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Critical Reviews in Biotechnology

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Spoilage Yeasts
Graham Fleet a
a
Department of Food Science and Technology, The University of New South Wales, Kensington, New South
Wales, Australia

Online Publication Date: 01 January 1992

To cite this Article Fleet, Graham(1992)'Spoilage Yeasts',Critical Reviews in Biotechnology,12:1,1 — 44

To link to this Article: DOI: 10.3109/07388559209069186
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 Critical Reviews in Biotechnology, 12( 112):1-44 ( 1992)

Spoilage Yeasts
Graham Fleet
Department of Food Science and Technology, The University of New South Wales, Kensington,
New South Wales, Australia

ABSTRACT: Yeasts are best known for their beneficial contributions to society, and the literature abounds
with discussions of their role in the fermentation of alcoholic beverages, bread, and other products. Yeasts also
cause spoilage, but, with a few exceptions, this unwanted activity often goes unrecognized and underestimated
as a major problem in the food and beverage industries. In some cases, there is only a fine line between what
is perceived as either a spoilage or beneficial activity. This review examines the occurrence and growth of yeasts
in foods and beverages with respect to their spoilage activities, the biochemistry of this spoilage, and technologies
for the enumeration and identification of spoilage yeasts.
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KEY WORDS: yeasts, spoilage, foods, properties, spoilage yeasts

I. INTRODUCTION from ethanol); however, the public health safety

of yeasts in foods may need some rethinking.
The presence of microorganisms in foods, There are occasional reports of gastroenteritis
beverages, and other commodities is significant from foods, wherein yeasts were suspected to be
to the human community for three main reasons: the causative agent. In addition, there is increas-
(1) the microorganisms may be pathogenic and ing evidence that some individuals develop al-
pose a risk to public health; (2) they may depre- lergic and other negative reactions to yeast^,^ and
ciate the sensory appeal of the product to the point this has led to the publication of significant lay
that it is considered spoiled and unacceptable; literature and the promotion of so-called “yeast
and (3) some species can effect desired changes free” diet^.^ As a consequence of this increased
in products, as in the production of fermented medical awareness, the inadvertent presence of
foods and beverages. Yeasts, as one group of yeasts in foods, whether they be spoilage species
microorganisms, are best known for their positive or otherwise, is likely to attract more attention
contributions to society, particularly through their in the future.
activities in the fermentation of bread, alcoholic Many studies have been published on the
beverages, and other products. Yeasts also cause spoilage of foods and beverages by yeasts, and
spoilage, but, with the exception of their effects these have been reviewed comprehensively on
on a few specific commodities, this negative at- several occasions.5-8 The thrust of this literature
tribute often goes unrecognized and underesti- has been ecological, essentially describing in
mated. The public health significance of yeast qualitative terms the main products spoiled and
contaminants in foods and beverages has been the species of yeasts responsible. Most reviewers
considered negligible. Infections from the few have concluded that yeast spoilage is limited to
known pathogenic yeasts, such as Candida a narrow range of products, especially those of
albicans and Cryptococcus neoformans, are not low pH or high sugar concentration, where com-
transmitted through foods. Moreover, humans petition from bacterial growth is restricted. Fleet
have been inadvertently consuming high popu- has reexamined the literature on spoilage yeasts
lations of viable yeast cells in fermented foods for foods generally9 and for dairy products spe-
and beverages for thousands of years without ob- cifically,1° and concluded that yeasts occur and
vious detriment to health (apart from intoxication grow in a greater range of products than previ-

0738-8551192/$.50
0 1992 by CRC Press, Inc.
1
 ously thought. It was also concluded that further erators. Bottles of tomato and other sauces, jams,
advances in understanding the spoilage activities and syrups that are opened and stored in kitchen
of yeasts would require a more quantitative ap- cupboards occasionally ferment. Slices of bacon
proach to studying their occurrence and growth and other varieties of preserved meats can de-
in specific products and more detailed investi- velop surface colonies of yeasts if stored too long
gations of their biochemical transformations. For in the refrigerator. Similarly, packaged fruit
these reasons, and because the ecological studies juices, opened and kept in the domestic refrig-
have been thoroughly covered,’-I0 the present re- erator, develop significant yeast populations if
view gives stronger emphasis to the biochemical not consumed within 5 to 7 d. Various cheeses
and physiological properties of spoilage yeasts. may quickly develop yeast populations of lo6 to
Information on the ecology of spoilage yeasts is los cells per gram after opening. The average
updated and presented in overview form to pro- consumer is largely unaware of these circum-
vide the appropriate background and orientation. stances and happily consumes these foods, seem-
Because of the importance of being able to ac- ingly without complaint or illness.
curately determine the populations and identities Most microbiological consultants have ex-
of spoilage yeasts, recent developments in tech- periences with yeast spoilage of products at the
nologies for conducting these measurements are industrial scale. This problem is not uncommon,
covered. The discussion is limited to foods and and the financial losses can be quite high. Prod-
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beverages and, in some cases feeds, and does not ucts often implicated involve fruit pulps, fruit
cover yeast spoilage of pharmaceuticals and juices, syrups, soft drinks, various sauces, al-
health-care products. “J* coholic beverages, and confectionery products.
Fleet’ has mentioned one example of yogurt
spoilage by yeasts, in which the cost of the out-
-
II. SPOILAGE RECOGNITION AND break was in excess of $100,000. For reasons of
ECONOMIC IMPLICATIONS commercial confidentiality, the incidence and
economic cost of industrial outbreaks of yeast
Changes in the sensory properties of foods spoilage remain unreported. In documenting the
do not become apparent to the consumer until costs of such outbreaks, consideration needs to
yeasts have grown to populations of lo5 to lo6 be given to (1) the value of the spoiled product,
cells per gram. These changes are most evident (2) the cost of recall and disposal, (3) subsequent
at populations of lo7to los cells per gram. How- decreased retailer and consumer purchase of the
ever, unless yeast growth is accompanied by very product because of tarnished reputation, and (4)
obvious physical effects such as swelling and the legal and insurance fees associated with de-
explosion of packages or gross alteration to prod- termining responsibility and awarding compen-
uct appearance, spoilage may go unnoticed. Apart sation. Usually, several parties represented by
from carbon dioxide, the major products of yeast manufacturers, suppliers of raw materials and
growth in foods are likely to be alcohols, organic packaging, and retailers are involved in these
acids, and esters.I3A large proportion of the com- cases.
munity will have positive associations with the
aromas and flavors of these substances through
their experiences in consuming fermented foods 111. SPOILAGE OF SPECIFIC
and alcoholic beverages. Consequently, many COMMODITIES
consumers may not interpret the unwanted oc-
currence of such substances in other commodities
as spoilage. A. Meats
In the author’s experience, foods obviously
affected by yeasts frequently occur at retail and Literature on the microbial spoilage of meats
domestic locations. Swollen containers of yo- is dominated by reference to the activities of bac-
gurts, cottage cheese, salads, and coleslaw are teria.14 Apart from the discussions by Jay’5 and
often seen in retail outlets and domestic refrig- Dalton et al. l6 and the more recent review of Fung

2
 and Liang,'6a very few studies have comprehen- Retail samples of minced or ground meat
sively addressed the occurrence, growth, and sig- contain variable populations of yeasts that range
nificance of yeasts in meats and meat products. from lo2to lo7cells per gram.'6,35-40 Yeasts read-
This lack of interest apparently originates from ily proliferate in comminuted meats during re-
the widely accepted view that bacteria grow much frigerated storage, but their final populations
better and faster on meat substrates than yeast (lo6 to lo7 cells per gram) remain insignificant
and, consequently, they will have a greater pres- compared to those of bacteria. Packaging under
ence and significance. While this view may be an atmosphere of carbon dioxide, but not nitro-
correct for fresh meats stored at refrigeration or gen, may restrict their Although yeasts
ambient temperatures, it may not be appropriate play only a minor role in the spoilage of ground
for processed meats or fresh meats stored under meats, their presence at lo6 to lo7cells per gram
other conditions. Bacterial growth on such meats may be significant to consumers who suffer yeast
may be restricted, thereby allowing increased allergies. The species most frequently isolated
growth and prevalence of yeasts. The following from refrigerated, comminuted meats include
discussion demonstrates a greater occurrence and Candida zeylanoides, C. lipolytica, C . famata
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significance of yeasts in meats and meat products (sporogenous equivalent, Debaryomyces han-
than previously considered. senii), C. sake, and Cryptococcus Zaurentii var.
Zaurentii (Table 1).
Long-term frozen storage of either lamb,41
1. Fresh Red and Poultry Meats beef,6 p o ~ l t r y ,or~ offal
~*~~ can give a
yeast-dominated spoilage flora that produces
Freshly slaughtered cuts of beef, '7-23 lamb,24-26 spoilage off-flavors. Under these conditions, low
Pork, '6.27728 p o ~ l t r y ,and
~ ~ alIigato?l
,~~ meats, as temperature and reduced water activity of the
well as offal r n e a t ~ ,harbor
~ ~ - ~low
~ populations meat surface combine to restrict bacterial growth,
(10' to lo3 cells per gram or square centimeter) allowing yeasts to multiply from initial popula-
of yeasts. There is limited growth of yeasts on tions of 10 to lo3 cells per square centimeter to
these meats during refrigerated (4"to 5°C) stor- lo6 to lo7 cells per square centimeter. For both
age, but the maximum populations formed rarely lamb4] and poultry,3o the dominant species at
exceed lo5 to lo6 cells per gram or square cen- spoilage were Cryp. laurentii var. laurentii and
timeter. The effect of packaging environment on C . zeylanoides (Table 1). Both species are li-
this growth requires more study, but it seems that polytic and this property could account for their
it is not encouraged by vacuum packaging and ability to spoil the meats. Spoilage of frozen meats
may be restricted by packaging under an atmos- by yeasts is probably more common than pres-
phere of carbon dioxide. 18-22.26.27 Overall, yeast ently thought. Further research is required to de-
populations on fresh and refrigerated carcasses termine the frequency of this problem and to con-
or cuts of carcasses represent only 5 to 10% of firm the role of yeasts in producing off-flavors
the total microbial flora and are insignificant in and taints in these products.
the spoilage process when compared with bac-
teria. However, conditions that suppress bacterial
growth on fresh meats, such as addition of an- 2. Processed Red and Poultry Meats
tibiotics or acidulents such as lactic, citric, and
acetic acids, will encourage yeast growth during In contrast to fresh meats, retail samples of
refrigerated tora age.^^.^^ Because of their low processed delicatessen-type meats are frequently
populations and general insignificance, the spe- contaminated with quantitatively significant pop-
cies of yeasts associated with fresh meats have ulations (105 to lo7 cells per gram) of yeasts.4245
not been the subject of detailed taxonomic study. Specific studies have been conducted with fresh
The most frequently encountered species are those and fermented sausages,16,46-51 bacon,52 frank-
of Candida and RhodotoruZa and, to a lesser ex- f u r t e r ~corned
, ~ ~ beef,42various cured h a r n ~ , ~ ~ - ~ *
tent, Saccharomyces and Debaryomyces (Table and haggis.59There is little doubt that yeasts pro-
1). liferate in these products during refrigerated stor-

3
 TABLE 1
Yeast Species Most Frequently Isolated from Meat Products

Product Yeast species Ref.

Fresh red and poultry meats Candida spp., Rhodotorula spp., Debaryornyces spp., 16, 75, 76
Trichosporon (not adequately studied)
Frozen lamb Cryptococcus laurentii, C. infirmo-miniatus, Candida 41
zeylanoides, Trichosporon pullulans
Frozen turkey Cryptmomus laurentii ,a Candida zeylanoides a 30
Ground/minced meat Candida lipolytica,a C. zeylanoides, C. larnbica, C. i6,37,3a
sake, Cryptococcus laurentii, Debaryornyces han-
senii, Pichia rnembranaefaciens
Processed meats (frankfurt- Debaryomyces hansenii, a Candida spp.” Rhodotorula 16, 17, 45, 51,
ers, sausages, hams, SPP. 52, 55, 77
bacon)
Fish Debatyomyces spp., Candida spp., Rhodotorula spp., 66-68. 74
C. /ipo/yticaa
Shrimp Candida spp., Rhodotorula spp., Trichosporon spp. 63-65
Shellfish Rhodotorula rubra, a Candida spp. 9, 72, 73
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Crabmeat Rhodotorula spp., Candida spp., Cryptococcus spp., 70, 71

Trichosporon spp.

a Indicates species associated with reports of spoilage; see also more extensive Tables in Jay‘” and Fung
and Liang.’”

age, especially if they have been vacuum pack- swelling of packaged, sliced meat^.^^','^ Other
aged.42,49*50Yeasts in vacuum-packaged corned less obvious but negative effects include the pro-
beef, for example, increased from lo3to 1O7 cells duction of off-flavor and taints, the production
per gram during storage for 15 d at 5°C.42Similar of metabolites such as acetaldehyde that can neu-
increases were reported during the refrigerated tralize the preservative effects of sulfur dioxide,
storage of British fresh sausage.I6 While such and the utilization of sodium nitrite that is added
growth appears significant, the final population as a curing agent and preservative. 16,2s However,
of yeasts may represent only 10% or less of the yeast growth may be desirable during the pro-
total flora. Packaging under carbon dioxide or duction of fermented sausages.mq61According to
nitrogen can prevent this yeast growth .47-49*s3 Grazia et al.,” the occurrence of D. hunsenii in
The species of yeasts associated with pro- Italian salamis has a positive effect on product
cessed meats are listed in Table 1. By far, De- quality.
buryomyces hansenii and its asporogenous form,
C. fumatu, are the most frequently isolated spe-
cies. In a survey of 200 Italian salami sausages, 3. Seafoods
for example, Grazia et al.51reported 82% of the
821 yeast isolates as D. hansenii. Unfortunately, Yeasts occur in aquatic environments at pop-
most of the studies listed in Table 1 do not report ulations of lo2 to lo3 cells per milliliter. This
quantitative population data for the species population, as well as the species present, varies
isolated. with proximity to land masses and the degree of
The significance of yeasts in processed meats pollution.62 It is not unexpected, therefore, that
will depend upon the product, but this subject the surfaces and intestinal contents of freshly
requires more detailed investigation. In some ~ - ~ ’ fish specie^,^^-^^
caught ~ h r i r n p s , ~various
products, yeasts cause spoilage. For example, c r a b ~ , ~and
~ * ~~h’e l l f i s h ’ ~harbor
* ~ ~ yeasts. Such
they may cause slimes and discoloration on the studies are too few and incomplete to draw gen-
surfaces of frankfurters and sausages, and gas- eral conclusions about the association of yeasts

4
 with seafoods, but it seems that the populations myces marxianus, Cryptococcusflavus, and Sac-
of yeasts in freshly caught products are usually charomyces cerevisiae readily grew to popula-
<lo3cells per gram or per square centimeter and tions of lo8 to lo9 cells per milliliter after
represent <5% of the total microbial flora. Table inoculation into sterilized milk.79Sweetened con-
1 indicates some species isolated from seafoods. densed milks are prone to gassy fermentation and
The ability of yeasts to grow in seafoods spoilage by yeasts because bacterial growth is
during refrigerated storage and cause spoilage restricted by the high concentration of sugar and
seems very minimal but exceptions may occur.71 low water activity of this p r o d ~ c t . ~There
, ~ is
Kobatake et al.74refer to an interesting series of some evidence that the so-called “health milks”,
Japanese studies that suggest yeasts have a more containing Lactobacillus acidophilus” or bifi-
significant role in the spoilage of seafoods than dobacteria,81will be particularly susceptible to
generally thought. In particular, they note that yeast spoilage.
some species of yeasts such as C . lipolytica may High-fat dairy products may be spoiled by
be just as important as spoilage bacteria in the yeasts, although the incidence of this problem is
production of volatile nitrogen bases in fish meats. rather low. lo Lipolytic species of Candida, Rho-
The pink or red discoloration of oyster meats dotorula, and Cryptococcus (Table 2) can grow
during frozen or refrigerated storage has been in and on the surface of butter,a4lead-
attributed to the growth of pigmented yeasts be- ing to the development of off-flavors. Residual
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longing to the genus R h o d o t o r ~ l a .A~ .clearer

~~ lactose in cream or sugar added to sweetened
picture of the role of yeasts in spoilage of sea- cream can be fermented by yeasts, causing a
foods and of their ability to grow in these prod- gassy, foamy a p p e a r a n ~ e .There
~ , ~ is very little
ucts under different conditions of storage must quantitative information on the occurrence of
await more quantitative ecological study of the yeasts in cream or butter. In a survey of retail
species present. creams purchased in Sydney, Australia, Fleet and
found 48% of samples with yeast counts
of lo3 to 10“ cells per milliliter and 14% with
B. Dairy Products counts of lo4 to lo5 cells per milliliter. Cream
samples stored at 5°C for 10 d increased their
Fleetlo recently reviewed the literature on yeast populations 100-fold.
yeasts in dairy products and concluded that their
significance in these products has been very much
underestimated. General discussions on the mi- 2. Yogurt
crobiology of milk and milk products focus on
the activities of bacteria and easily mislead the During the last 30 to 40 years, yogurts have
reader into thinking that yeasts are relatively un- become a popular product in many countries.
important in the dairy industry. Marth78has pro- This increased popularity stems from the addition
vided another account of the occurrence and sig- of sugar, fruits, flavors, and other ingredients to
nificance of yeasts in dairy products. the basic formulation. Spoilage of yogurts by
yeasts has emerged as a major problem in the
dairy i n d u ~ t r y .The
~ ~ ,yeasts
~ ~ originate from the
7. Milk, Cream, Butter ingredients, especially fruits, but also from pro-
cessing equipment that has not been properly
Yeasts occur in raw and pasteurized milks at cleaned and sanitized. Starter cultures of lactic
low populations, generally <lo3 cells per mil- acid bacteria used to ferment the yogurt are an-
liliter. These yeasts rarely grow in milk during other potential source of yeast contamination.
refrigerated storage, and are quickly overgrown When produced under conditions of good man-
by psychrotrophic However, in the ufacturing practice, yogurts should contain less
absence of significant bacterial competition, than one yeast cell per gram. They should not
yeasts can establish very good growth in milk. undergo spoilage by yeasts and should have a
Thus, several species of Candida, KZuyvero- refrigerated shelf-life of 3 to 4 weeks or longer.

5
 TABLE 2
Yeast Species Most Frequently Isolated from Dairy Products

Product Yeast species Ref.

Raw/pasteurized Rhodotorula spp., Candida famata, C.diffluens, C. 6 , 7, 79, 109

milks curvata, Kluyveromyces marxianus, Cryptococcus
flavus (few ecological studies conducted)
Cream and butter Rhodotorula rubra, R. glutinis, Cryptococcus laurentii, 6, 7, 79, 82-84
C. diffluens, C. famata, C. lipolytica (few ecological
studies conducted)
Yogurts Kluyveromyces marxianus, C. famata, other Candida 79, 85-88, 110
spp., Debaryomyces hansenii, Saccharomyces
cerevisiae, Hansenula anomala
Cottage and Kluyveromyces marxianus, C. lipolytica, other Can- 79, 95-97
fresh cheese dida spp., Cryptococcus laurentii, Sporobolmyces
roseus
Mold-ripened soft Kluyveromyces marxianus, D. hansenii, C. famata, C. 99- 108
cheeses lipolytica, Pichia membranaefaciens,P. fermentans,
Saccharomyces cerevisiae, Zygosaccharomyces
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rouxii

However, surveys of retail yogurts in several 3. Cheese

countries have revealed a high incidence of yeast
contamination, with many samples (20 to 60%, Reports on the occurrence of yeasts in cheeses
depending on the report) harboring yeast popu- date back to the early part of this century and a
lations of lo3 cells per gram or more. In some sizeable literature on the subject has since ac-
cases, yeast counts of lo6 to lo7 cells per gram cumulated.10.90Nevertheless, it is not widely ap-
have been recorded. 10.7935-89 Spoilage becomes preciated that yeasts can be an important com-
evident when yeast populations reach lo5 to lo6 ponent of the microflora of many, if not all, cheese
cells per gram, and is first recognized as a swell- varieties. There are numerous references to the
ing of the yogurt package due to gas production occurrence of yeasts in retail samples of soft,
by yeast fermentation. The yogurt acquires a semisoft, semihard, and hard cheeses. It is not
yeasty, fermented odor and flavor and a gassy unusual to find yeast counts of approximately 10'
appearance. The package eventually ruptures. to lo6 cells per gram and, in some varieties,
Sometimes, colonies of yeasts can be seen on the counts as high as lo7 to lo8 cells per gram are
undersurface of the package lid. lo Procedures for often reported.
controlling yogurt spoilage are discussed by Cheese manufacture involves three main
Davisx5 and Fleet.lo The main species of yeasts stage^:^^.^'
isolated from yogurts are shown in Table 2, with
species of Candida and Kluyveromyces being most 1. Production of a curd by fermentation of milk
prevalent. The predominance of any particular with lactic acid bacteria and by the addition
species in yogurts is related to its ability to (1) of proteolytic enzymes
grow at low temperatures (5" to 10°C) of yogurt 2. Further processing of the curd by heating,
storage; (2) produce lipolytic and proteolytic en- addition of salt, and, in some cases, inoc-
zymes that hydrolyze milk fat and protein; (3) ulation with specific bacteria or fungi
ferment lactose or sucrose, which are the main 3. Maturation of the curd by storage at low
carbohydrates of either natural or flavored yo- temperature.
gurts; and (4)utilize lactic and citric acids, the
main organic acids of y o g ~ r t . ~ ~ , ~ ~ Yeasts grow as natural contaminants in the curd

6
 during the stage of maturation. They are insig- yeast populations as high as 10' cells per gram
nificant at the earlier stages of production. During are not u n u ~ u a l . ~ ~A~mixed
' ~ ' ~ 'population
~~ of
maturation, the cheese presents an environment oxidative and fermentative species (Table 2)
of low pH, low moisture content, elevated salt grows within the curd and on the surface of the
concentration, and low temperature. These con- curd. The kinetics of growth varies according to
ditions are very favorable and selective for yeast location in the curd, yeast species, and the variety
growth. The significance of this growth depends of cheese. In particular, the salt concentration
upon the cheese. In some varieties they make a used in the manufacture of these cheeses can vary
positive contribution to the development of flavor between 5 to lo%, and in our observations (un-
and texture. published data) this will significantly affect the
Ingram6 and Walker and Ayres7 reviewed profile of yeast growth. A more accurate under-
early studies that describe the spoilage of Ched- standing of the growth of individual species
dar and Swiss cheeses by yeasts. More recent throughout maturation is required.
reports include the spoilage of processed cheese Other cheese varieties in which yeasts grow
by D. hansenii,'* Australian Cheddar by a Can- during maturation include Cabrales, Limburger,
dida s ~ .and , ~Parmesan
~ by Kluy. marxian~s.'~ Brick, Trappist, Kopanisti, Saint-Nectaire,
The main defects attributable to yeast activity are Gruyere, Cantal, and roman^.^^^'^-'^^ The Lim-
burger, Brick, and Trappist varieties are semisoft
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fruity, bitter, or yeasty off-flavors and gassy,

open texture with semihard or hard cheeses. As- cheeses that involve predominant surface growth
sessment of cheese spoilage is complicated by of the bacterium Brevibacterium linens during
subjective judgments as to whether yeast activity maturation. The growth of this bacterium does
during maturation and retailing is detrimental or not occur until yeasts have grown in the curd and
beneficial to product quality. Continued lactose its pH has increased to approximately 5.7 by
fermentation by yeasts at these stages leads to metabolizing lactic acid. Io5
increased acidity, gassiness, and fruit flavors, The main species isolated from soft cheeses
while continued hydrolysis of protein and fat soft- during maturation are D . hansenii, Kluy. marx-
ens the texture of the product and produces bitter ianus, C . famata, C . lipolytica, Pichia mem-
and rancid flavors. With cottage cheese or similar branaefaciens, P. fermentans, and other species
types of unripened soft cheeses, such as quarg, of Candida (Table 2). The same species are also
there is little doubt that yeasts cause spoilage. isolated in high populations from retail samples
Yeast populations of lo6 to lo7 cells per gram of these c h e e ~ e s . ~ ~ . ' ~ . ' ~ ~
frequently develop during refrigerated storage of There are several mechanisms by which yeast
these products leading to flavor and odor defects growth is thought to influence the maturation pro-
and g a s s i n e s ~ .The
~ ~ species
- ~ ~ implicated in such cess and the final quality of cheese:w~'08
spoilage are shown in Table 2. It is likely that
the soft, brined cheeses such as Feta and Domiatiy8 1. Fermentation of residual lactose within the
are prone to yeast spoilage, but the microbiology curd by species such as Kluy. marxianus
of these products has received little attention. produces secondary (flavor) metabolites as
Yeasts have a special association with the well as carbon dioxide gas that opens up
semisoft, mold-ripened cheeses such as Roque- the curd texture. In the case of blue-veined
fort, Danish Blue, Gorgonzola and Stilton (the cheeses, opening up and aeration of the curd
blue-veined cheeses), and Camembert and Brie. is considered desirable because it encour-
Retail samples of these cheeses have a very high ages growth and vein development by
incidence of yeast presence, with most samples P . ruqueforti.
exhibiting counts exceeding lo6 cells per 2. Utilization of Iactic acid is a major conse-
gram.yy.lOO The curd of these cheeses is inoculated quence of yeast growth in cheeses. This
with either Penicillium ruquefurti or P. camem- action decreases acidity of the curd (which
berti just prior to maturation.y' Growth of the may be a desirable sensory attribute by it-
mold is accompanied by extensive growth of nat- self) and increases its pH to a value that can
ural yeast flora during maturation, and maximum encourage the growth of "maturation" bac-

7
 teria. Moreover, the change in pH could ulations when they occur in association with high
affect the activity of lipases and proteases populations of molds (see Section V). In the au-
produced by the Pencillium species. thors view, the microbial ecology of fruit spoil-
3. The activity of extracellular proteases and age is an area of food biotechnology that needs
lipases produced by some yeast species, such rigorous scientific investigation to better under-
as C. lipolytica, could alter curd flavor and stand the interactions between fungi, yeasts, and
texture. bacteria. This need will become more evident as
4. The release of autolytic products by yeasts new technologies for packaging, storage, and
can influence flavor, as well as encourage biocontrol are developed to extend shelf-life and
the growth of bacteria. add value to fresh fruit. The same comments
would apply to fresh vegetables (see Section
1II.E).
Although these influences of yeasts seem very As reviewed by several a u t h o r ~ , "'I6~ yeasts
logical, key experiments that link the growth and commonly occur on the surfaces of freshly har-
activity of particular species to a sensory outcome vested fruits at populations of lo3to lo5cells per
remain to be done. It is important to realize that square centimeter. Martini and Martini'" have
the yeast flora that develops during maturation questioned the reliability of earlier ecological data
is a relatively uncontrolled mixture of wild spe- because of inadequate procedures used for dis-
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cies. While some species may benefit cheese lodging yeasts from fruit surfaces for subsequent
quality, others may have a detrimental effect. measurement. In most circumstances, this sur-
Further research must identify the desired and face flora of yeasts is considered to remain rel-
undesired species. When this information be- atively inactive as the species present do not pro-
comes available, it may be possible to select con- duce the appropriate cellulolytic and pectinolytic
ditions that specifically encourage the growth of enzymes to degrade the skin of the fruit and es-
the desired species, or to add them as starter tablish However, physical damage
cultures. Both D . hansenii and C . lipolyfica have of the skin by overripening, mechanical injury,
been suggested as potential species for deliberate or fungal attack exposes the fruit tissue upon
use in cheese maturation.'0.90 which yeasts can rapidly grow. Damaged fruit
frequently harbors yeast populations of lo6to 10'
cells per gram, but the kinetics and significance
C. Fresh Fruits of this growth in relation to the total process of
spoilage, and especially fungal development, are
The visible presence of fungal mycelium and not clear. Nevertheless, there are occasional re-
spores on the surface of fruits at the time of ports that testify to a more active role of yeasts
rotting has led to the well-accepted conclusion in fruit spoilage. These include:
that molds are mostly responsible for the spoilage
of these products."l Books on the postharvest 1. The fermentative spoilage of strawberries
spoilage of fruit focus on the activities of molds by Kloeckera apiculata' I')
and rarely consider any contribution from 2. Fermentation of tomatoes by Hansenias-
yeast^."^.^'^ While yeasts may not be the main pora uvarum, K . apiculata, and Pichia
pioneers or initiators of fruit spoilage, it seems kluyveri120
unusual that they are not more frequently de- 3. Spoilage of figs by apiculate yeasts, Can-
scribed as part of the spoilage flora. They com- dida stellata, and C . krusei"'
monly occur on the surfaces of fruits at harvest, 4. The association of K . apiculata, P . fer-
and the low pH and sugary composition of fruit mentans, and P . kluyveri with necrotic
tissue presents a most conducive environment for oranges'22
their growth. It is very likely that the real con- 5 . Rotting of rhubarb by Trichosporon
tribution of yeasts to the dynamics of fruit spoil- cutaneum ' '*
age has been overlooked because of the technical 6. Spoilage of pineapples by H . guilliermondii
difficulties that can arise in measuring yeast pop- and C . g ~ i l l i e r m o n d i i l ~ ~

8
 7. The association of K . apiculata, C. krusei, vent yeast growth. The yeasts originate from the
Metschnikowia pulcherrima, and Sacchar- surface of the fruit and improperly cleaned pro-
omycopsis crataegensis with sour rot in cessing equipment. The yeasts responsible for
grapes. Iz4 this fermentative spoilage have been well studied
for apple, 133~134g r a ~ e , ' ~and
~ - orange6*'
'~~ juices.
Long-term storage of frozen fruits may select Species of Kloeckera, Hanseniaspora, Candida,
for the growth of spoilage yeasts but there are and Hansenula initiate the fermentation, but are
few studies on this to pi^.^^^ As briefly noted by soon overgrown by more ethanol-tolerant strains
Golden et al. shrink-wrapping is another pro- of Saccharomyces cerevisiae. Final yeast popu-
cess that could encourage the growth of yeasts lations of lo7 to lo9 cells per milliliter easily
on fresh fruits, but this possibility requires more develop in these juices. Refrigerated (0" to 5°C)
study. storage of the juice will retard but not prevent
A recent and most exciting discovery has yeast spoilage. The spoilage flora of refrigerated
been the isolation from fruits of yeast species that juices might include a greater presence of Kloeck-
exhibit antifungal activity.126-128 Such yeasts in- era and Candida species because the ethanol tol-
clude Cryp. Eaurentii, D. hansenii, and Candida erance of these yeasts is enhanced at lower tem-
sp., and currently they are being examined for peratures.136~137The addition of preservatives such
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potential use as agents for the biocontrol of fruit as sulfur dioxide, benzoic acid, or sorbic acid,
spoilage fungi. The fact that these species have combined with refrigeration will further extend
been isolated from the surfaces of fruits rein- shelf-life, but yeast spoilage is inevitable.138.139
forces the need for more comprehensive study of In these circumstances, the preservative resistant
the microbial ecology of fruits and fruit spoilage. yeast, Zygosaccharomyces bailii, often domi-
nates the spoilage flora.'"O Fleet and Mian (un-
published data) and SandI4' reported interesting
D. Processed Fruits examples of yeast growth in refrigerated fruit
juice dispensers or fountains frequently seen at
Yeast spoilage is a major problem to indus- "fast food" outlets. Yeast populations as high
tries that process fruits. Products of interest in- as lo6cells per milliliter were found, with a dom-
clude fruit juices, fruit juice and fruit pulp con- inant presence of Zygosacch. bailii, Sacch. cere-
centrates, canned fruits, glacCd fruits, and ready- visiae, and Candida sake.
to-eat fruit slices and fruit salads. Carbonated soft Storage of fruit juice or fruit pulp as frozen
drinks are included here because many of these concentrates is an effective means of controlling
use fruit extracts as a base ingredient. Informa- yeast spoilage. 130*132The sugar concentration of
tion on the occurrence, growth, and control of these products is in the range of 45" to 65" brix
yeasts in processed fruits has been well re- and, in combination with storage temperatures
viewed.118-129-132 However, new developments and <O"C, this factor prevents yeast growth. How-
directions in fruit processing demand continued ever, yeasts will grow in these concentrates if
study of yeast associations. These developments the storage temperature increases above 5°C.
include the use of enzymes and membrane fil- Yeasts reported to grow under these conditions
tration in processing, new packaging technolo- include the osmotolerant species of Zygosacch.
gies, the introduction of new products such as rouxii, Hanseniaspora valbyensis, C . krusei, and
"ready-to-eat'' sliced fruits and fruit salads, and other Candida species.142-144
an increasing demand by consumers for less use Heating is one of the main processes used
of preservatives in processing these products. for controlling yeast spoilage of fruit juice, fruit
Also, processed fruits are used as ingredients in concentrates and soft drinks. Outbreaks of spoil-
other commodities such as yogurts and frozen age of these products have stimulated consider-
fruit pies, and they can be a major source of yeast able research into factors that affect the resistance
contamination and spoilage of these products. of yeasts to heat destruction.145-147 Apart from the
Freshly extracted fruit juices quickly undergo temperature and time of treatment, significant
alcoholic fermentation unless processed to pre- variables include the concentration of sugar in

9
 the product, the presence of any preservatives, Yeasts are invariably active during the fer-
and the heat resistance of yeast ascospores (see mentation of brined vegetables such as sauer-
Section 1V.J). Saccharomyces cerevisiae, Zyg- kraut, olives, and pickles.1S2J65Although lactic
osacch. huilii, and occasionally species of Bret- acid bacteria are primarily responsible for the
tanomyces and Candidu are the yeasts mainly fermentation, the presence of salt and the reduced
responsible for the spoilage of heat processed pH created by the production of lactic acid select
fruit juices and soft drinks. 13”,148.149 for the healthy growth of yeasts during the main
Yeast spoilage of other fruit products such stages of fermentation and during postfermen-
as dried dates, prunes and figs, glackd fruits, and tation. Fermentative species of yeasts grow in the
sulfited fruits is well described in the litera- depths of the brine and oxidative species grow
’ . ”yet,
t ~ r e . ~ ~As ~ there is little baseline data on on the surface. Species from both groups produce
the occurrence and growth of yeasts in some of flavor defects in the final product, and, in ad-
the newer fruit products such as the “ready-to- dition, the oxidative yeasts utilize lactic acid,
eat” fruit salads, fruit slices, and fruit peels.150~’s1 thereby increasing pH and encouraging the growth
However, it seems likely that yeasts will be sig- of spoilage bacteria. Other spoilage characteris-
nificant in determining the quality and shelf-life tics caused by yeasts include discoloration, soft-
of these products. ening, gaseous blistering, and bloating. 118s152Pink
discoloration of sauerkraut is caused by species
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of Rhodotorula. Softening of product texture is

E. Fresh and Processed Vegetables caused, in part, by pectolytic enzymes produced
by species of Debaryomyces, Pichia, Candida,
Little is known about the yeast ecology of Saccharomyces, and Rhodotorula. Ibb Swelling
fresh vegetables and any role that yeasts might and blistering in olives and pickles are the result
play in the spoilage of these products.152Yeasts of excessive gas production by Saccharomyces
are certainly part of the flora of vegetables, as and Hansenula sp.Il8 However, not all of the
reported for cabbage,153+154 lettuce,’ss corn ker- yeast species that grow during vegetable fermen-
nels,Is6 and various sliced products. 157-159The tations cause spoilage; although rarely stated, it
populations are generally low (around lo3to lo4 is likely that some species will make a positive
cells per gram), but they may increase during contribution to product quality.
storage, especially if the product is sliced or “Ready-to-eat” or “take-away’’ vegetable
shredded. Yeast counts of lo8cells per gram have salads, such as coleslaw or potato salad, present
been reported in stored cabbages, with Cryp. al- an interesting example of yeast spoilage. Retail
bidus, Cryp. laurentii, Cryp. macerans, and Spo- samples of these salads frequently have yeast
robolomyces roseus being the most prevalent spe- populations of lo6 cells per gram or higher and
cies. 152-154 can show evidence of spoilage through the de-
Fungi and bacteria are considered to be the velopment of off-flavors, gassiness, and surface
main perpetrators of fresh vegetable spoil- colonies of y e a ~ t s . I ~ ~Mayonnaise,
-I~l used as a
but more careful ecological study of base in preparing many of these products, lowers
the spoilage flora is likely to reveal a greater pH, making them a selective environment for the
contribution by yeasts. Several recent studies growth of yeasts. Species reported to grow in
demonstrate this possibility. The spoilage of these salads during refrigerated storage include
“ready-to-use” grated carrots is caused by the Sacch. duirensis, Sacch. exiguus, P . membran-
combined growth of lactic acid bacteria and aefaciens, C . sake, C . tambica, C . lipolytica,
yeasts. 16” Soft rot in onions, usually attributed to and C . zeylanoides. 118*169.170
the growth of the bacterium, Erwinia carotovora,
is also caused by Kluy. marxianzis.161,162 Rho-
dotorula glutinis has the potential of spoiling peas F. Foods Containing High
during frozen storage. 163 Shrink wrapping and Concentrations of Sugar or Salt
gas packaging encouraged the growth of yeast
and molds during the storage of fresh bell pep- Foods containing high concentrations (40 to
pers; these organisms did not grow on unpack- 70%) of sugar include sugarcane, syrups, honey,
aged peppers. lM molasses, maple syrup, malt extract, fruit juice
10
 concentrates, jams, jellies, conserves, confec- and similar sauces by Zygosacch. bailli, P . mem-
tionery products, and dried fruits. If contami- branaefaciens, and C. krusei. 1 8 2 ~ 1 8 3
nated with particular species of yeasts and in-
adequately processed and stored, they will
undergo fermentative spoilage to acquire an es- G. Bakery Products
tery fruity character and a gassy, frothy texture.
Packaged, products may swell and explode. Although yeasts are primarily responsible for
TilburyI7' has given a detailed account of the the fermentation of bakery products, they can
yeast spoilage of these products. More recent also cause their spoilage (for reviews, see Seiler'&
surveys of the presence of yeasts in high sugar and Ponte and T ~ e n ' * ~Breads
). may develop a
foods have been published by Tokuoka et a1.'73 range of alcoholic, fruity, and acetone-like off-
and Jermini et al.174Almost invariably, the high flavors, and, in the case of dark varieties, a spec-
concentration of sugar and resultant low water kled chalky discoloration as well. Yeasts re-
activity (Aw <0.85) select for the growth of only sponsible for such problems include Hansenula
one species, namely, Zygosacch. rouxii, and anomala var. anomala, Endomycopsis burtonii,
populations as high as lo6 to lo9 cells per gram Hyphopichia sp., and Sacch. cerevisiae. 1843186

may develop. 1749175On some occasions, osmo- Yeasts can grow to spoilage populations during
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tolerant strains of Zygosacch. bailii, D.hansenii, the refrigerated storage of unbaked bread, pastry,
Torulaspora delbrueckii, H. anomala, and Schi- biscuit, and pizza doughs. 187,188Yeast contami-
zasuccharomyces sp. have been isolated from nation originates from the pastry ingredients and
these types of products. ' 7 3 ~ 1 7 4 fillers and toppings (e.g., olives and cheese in
In contrast to high-sugar foods, there have the case of pizzas). The species associated with
been fewer studies on the yeasts specifically as- these types of products have not been identified.
sociated with foods containing high concentra- Frozen or refrigerated fruit pies or turnovers are
tions of salt. High-salt (5 to 15%) environments obvious targets for yeast spoilage. The spoilage
occur during the production of fermented, brined of apple turnovers by Sacch. cerevisiae has been
vegetables and some cheeses, and the yeasts as- reported.lE9Yeast growth can occur in the jam,
sociated with these products are discussed in Sec- fruit, and cream fillings of cake A
tions I1I.B and 1II.E. O n i ~ h ihas ' ~ ~reviewed the problem not mentioned in the literature, but ev-
growth of yeasts in soy sauce and miso, which ident from our own studies, is the potential con-
contain salt at concentrations of 10 to 20%. The tamination of commercial baker's yeast (Sacch.
most dominant yeasts in these products are Zyg- cerevisiae) with wild yeasts. However, for some
osacch. rouxii, D . hansenii, C . famata, other of the more traditional sourdough and other types
Candida sp., Pichia sp., and Hansenula subpel- of breads, yeasts other than Sacch. cerevisiae
liculosa. Yeasts appear to be associated with the may be important in contributing to the Gnique
salted fish products of Asian and Southeast Asian characteristics of the product. 190-192
countries, but taxonomic studies of the main spe-
cies present are lacking. 177 Less obvious high-
salt environments are the aqueous phases of H. Alcoholic Beverages
margarine^'^^ and m a ~ o n n a i s e sin'~~ which con-
centrations of 10 to 12% salt are found. Lipolytic 1. Beer
spoilage of margarines by C. lipolytica has been
and presumably this species can tol- The wort used for fermentation into beer is
erate the 10 to 12% salt. Spoilage of mayonnaise relatively sterile because of the boiling process.
and salad dressing by Zygosacch. baitii is well The fermentation is conducted by inoculation of
described.179-'81 In addition to tolerating the salt a relatively pure culture of the desired strain of
and sugar concentrated in the aqueous phase, this Sacch. cerevisiae. Accordingly, beer spoilage by
species is also resistant to the high concentrations yeasts should not be a problem to the brewing
of acetic used in formulating these products. industry. Nevertheless, experience has shown that
Somewhat related is the spoilage of tomato sauce if good manufacturing and good quality assur-

11
 ance practices are not following, beer can be Sacch. cerevisiae for conducting the fermenta-
spoiled by the growth of wild yeasts, i.e., species tion. One particular strain may create a desired
or strains other than the one inoculated into the style of beer under one set of fermentation con-
wort. Principally, wild yeasts gain access to the ditions, but a less desired product under different
beer as contaminants of the pitching (inoculum) conditions.19* Since the brewery may be working
yeast, but they also originate from improperly with several different strains in producing a range
cleaned equipment and from ingredients or pro- of beer varieties, the potential exists for cross-
cessing aids used after fermentation. Spoilage contamination between strains and the inadvert-
can occur (1) in the finished product, (2) during ent use of the wrong strains. Such problems may
conditioning or maturation of the beer in tanks be viewed as a more subtle form of yeast spoil-
prior to packaging, and (3) to a lesser extent, age. In a similar context, vigilance is required to
during fermentation. The ecology and mecha- ensure that unwanted killer strains of Sacch. cere-
nisms of beer spoilage by yeasts have been well visiae do not contaminate the pitching yeast. Such
reviewed,193-19s with few advances in knowledge strains can alter the conduct of the fermentation
in recent years. and depreciate beer quality. 199.200 The elevated
Yeast spoilage of bottled or canned beer is importance of strain selection in modem brewing
rarely a problem these days, if proper heat pas- places new demands on quality-assurance pro-
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teurization or aseptic packaging have been con- grams to adopt advanced technologies for veri-
ducted. Failure in these processes can lead to fying the strain homogeneity of the pitching
fermentative spoilage, giving turbidity, sedi- yeast. 198
ment, and gassiness in the product. Generally, Some beers, such as those prepared in Af-
species of Saccharomyces are responsible, with rican countries,2o1and the lambic and gueuze beers
Sacch. diastaticus being of special concern be- prepared in Belgium,197are still produced by tra-
cause of its ability to ferment the residual starch ditional fermentations that involve the growth of
dextrins of the beer.196Draft beer in barrels is a mixture of yeast species. The African sorghum
more prone to spoilage because it is not heat beers are characterized by the predominant growth
pasteurized, and requires careful handling during of Sacch. cerevisiae as well as strong contribu-
retailing and dispensing. It may undergo fer- tions from a wide range of Candidu species. The
mentative spoilage by species of Saccharomyces, growth of B. intermedius in these beers, how-
and, if it is exposed to air, oxidative yeasts such ever, produces a poor-quality product.201In con-
as P . membranaefaciens, P . fermentans, H . an- trast, Brettanomyces species, in conjunction with
omala, and various Candida sp. may grow on K1. apiculata and several species of Saccharo-
the surface to spoil the product.193.195 myces, play a key role in the production of char-
Beer is most vulnerable to yeast spoilage dur- acteristic lambic and gueuze beers. 197
ing the stage of conditioning or maturation, when
it is held in tanks at refrigeration temperatures
for several days or weeks. The microbial ecology 2. Wine
of this part of the brewing process has not re-
ceived the same degree of attention as other stages Although yeasts are primarily responsible for
and warrants more detailed consideration. How- the alcoholic fermentation of grape juice and other
ever, undesirable strains of Sacch. cerevisiae, juices into wines, their uncontrolled growth leads
other species of Saccharomyces (e.g., Sacch. to significant wine spoilage. This growth and
diastaticus), species of Brettanomyces, and fer- spoilage can occur at several stages of produc-
mentative species of Candida can produce marked tion: in the finished product, during alcoholic
off-flavors.193+195 Succh. diastaticus gives phe- fermentation, and during bulk storage of the wine
nolic off-flavors and Brettanomyces species can in cellars prior to packaging. Outbreaks of wine
give undesirable acetic acid and estery spoilage, the yeast species responsible, and meth-
character. 197 ods for controlling this problem are well re-
Modem brewing practices have become very viewed.202-2fls Nevertheless, recent advances in
strain oriented with respect to the selection of knowledge about the microbial ecology and bio-

12
 chemistry of wine fermentations demand reex- as for Sacch. cerevisiae, there is likely to be
amination and reevaluation of the role of yeasts considerable strain variation within each species.
in causing wine spoilage.206This task is too large Some strains of Kl. apiculata and H . anomala,
for the present review, but the following com- for example, may produce undesirably high con-
ments will indicate the general scope of the centrations of ethyl acetate. 2043205 Saccharomy-
problem. codes ludwigii produces high concentrations of
The incidence of yeast spoilage of bottled or aceteldehyde.205 While the controlled growth of
"bag in the box" wines has decreased in recent these indigenous species may in some circum-
years because of increased packaging by sterile stances enhance the chemical complexity and
filtration. However, spoilage outbreaks still oc- sensory quality of wines, there are other circum-
cur, with ethanol tolerant and sulfur dioxide tol- stances in which their contribution may be spoil-
erant strains of Zygosacch. bailii and Sacch. age. Recent findings that the killer character can
cerevisiae being the main causative organisms. occur in wine strains of Sacch. cerevisiae2"jand
These species ferment residual sugar in the wine, in strains of indigenous non-Saccharomyces
producing turbidity, sediment, and gassiness. yeasts2I7introduce further possibilities of spoil-
Packaged wine containing these yeasts at popu- age during the stage of alcoholic fermentation.
lations as low as 5 to 100 cells per liter are likely Objectionable taints to flavor can easily de-
to spoil. 140,207,208 velop during bulk storage of wine in cellars, un-
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A little over 100 years of empirical and sci- less sound hygienic practices are followed. Wines
entific research has shown that Sacch. cerevisiae exposed to air quickly develop a surface flora of
is the most desirable species for conducting the film yeasts that oxidize ethanol and produce un-
alcoholic fermentation of wines. Although this desirable concentrations of acetaldehyde, esters,
species eventually dominates in fermentations al- and volatile acids. Species of Candida and Pichia
lowed to proceed naturally, many winemakers are principally involved in this type of spoilage
encourage its presence and growth by inoculation but the fermentative yeasts Saccharomycodes
of the juice with commercial preparations of this ludwigii and Brettanomyces sp. can also be trou-
organism.2wIt is now recognized, however, that b l e ~ o r n e . The - ~ ~ ~of B. intermedius in
~ ~ ~growth
considerable strain variation occurs within this wines has been connected with the production of
species; while some strains produce wines of de- excessive acetic acid and substituted tetrahydro-
sirable quality, others produce wines with objec- pyridines that confer a distinctive mousy taint . 2 1 8
tionable concentrations of metabolites such as In addition, this species produces volatile phe-
sulfides or volatile acids .2w-212
Another unwanted nolic derivatives such as 4-ethyl guaiacol and 4-
character of some strains is the generation of ethyl phenol that give distinctive, unwanted taints
excessive foam during f e r m e n t a t i ~ n . ~In~these
~.~'~ described as spicy, medicinal, and
contexts, some strains of Sacch. cerevisiae are
clearly in the category of spoilage yeasts.
The early stages of most wine fermentations, I. Grains and Grain Silage
whether they develop naturally or after inocula-
tion with Sacch. cerevisiae, are characterized by Yeasts of the genera Candida, Cryptococcus,
the significant growth of indigenous species of Rhodotorula, and Sporobolomyces are frequently
non-Saccharomyces yeasts. Prominent among isolated from grains prior to harvest,6.220.2*'but,
these yeasts are species of Kloeckera, Hansen- like many other commodities discussed in this
iaspora, Candida, Pichia, and Hansenula. 135*215 review, the significance of this presence has not
The degree to which these species contribute to been seriously considered. Fungi are considered
the overall fermentation varies, depending upon to be the main agents of pre- and postharvest
vinification factors such as extent of juice clar- spoilage of grains.222*223 Nevertheless, recent ob-
ification, temperature of fermentation, and use servations suggest that yeast association with
of sulfur dioxide.137,206As yet, it is not clear how grains might be more important than generally
the growth of these yeasts affects the chemical thought. has noted a strong and possibly
composition and final sensory quality of the wine; commensalistic association of Candida guiltier-

13
 mondii with the fungal species Fusarium moni- Under these conditions, the yeasts metabolize
liforme and Aspergillus f l a w s during the moldy lactic and acetic acids, the main acids of silage,
spoilage of preharvest corn. The spoilage of grains causing the pH to increase and encourage the
during postharvest storage in silos is initiated when growth of spoilage bacteria. 221 The yeast species
they are not sufficiently dried or become wet. associated with silage depend on the raw material
The author has often noticed strong, fermentative In the case of maize silage, the pre-
alcoholic odors emerging from such grains; it dominant species at both fermentation and spoil-
would be surprising not to find yeasts as part of age have been reported as Candida holmii, C .
the spoilage flora. In this respect, A y e r ~ briefly
t~~~ milleri, C . krusei, C . lambica, C . famata, H .
noted the significant occurrence of yeasts, such anornula, Sacch. dairensis, and Sacch. exig-
as Hansenula sp., in moist grains stored at low uus.221.227,228
For wheat and alfalfa silages, the
temperatures. Interestingly, both Ingram' and main yeasts associated with aerobic spoilage of
Walker and Ayres7 refer to several early studies the products were Endomycopsis burtonii, E. se-
where yeasts (Endomycopsis chodati, H . anom- lenospora, Hansenula canadensis (in wheat only),
ala, P . farinosa, C . tropicalis, and C. pseudo- Candida tenvis. and Candida sulvicola.22'
tropicalis) were implicated in the spoilage of
stored rice. Yeast populations as high as lo7cells
per gram were capable of developing in these J. Miscellaneous Fermented Products
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cereals. On the basis of these few reports, it seems

that the association of yeasts with the pre- and In addition to the fermented products men-
postharvest deterioration of grains needs further tioned previously, there are many other examples
investigation, especially in the direction of in- where the growth of yeasts contributes signifi-
teractive relationships between yeasts and other cantly to the microbial ecology of the fermen-
fungi. tation. Many of these products are produced in
Flannigan22"has reviewed the microbial ecol- developing countries by traditional methods, and,
ogy of barley, with special reference to the to a large extent, the fermentations represent the
changes in flora that occur during the malting uncontrolled growth of indigenous species. Ov-
process, Although bacteria predominate during ergrowth of yeasts during fermentation or inad-
the steeping and germination stages of malting, vertent growth of the wrong species can readily
yeasts grow to populations of lohto lo7cells per compromise product quality. Unfortunately, for
kernel. The predominant species in green malt a majority of these products, the yeast ecology
were Candida catenulata and D . hansenii while of the fermentation is not accurately known. The
Rhodotorula mucilaginosa and C . catenulata were following examples are presented to draw atten-
prevalent in screened malt. 224.22s tion to the significance of yeasts in these types
It is now evident that yeasts play a significant of foods.
role in the production and spoilage of grain silage Cocoa beans are subject to fermentation be-
for animal feed. The details of silage production fore manufacture into chocolate. There is no doubt
have been reviewed by Woolford.226Although that the sensory characteristics of chocolate are
lactic acid bacteria are primarily responsible for intimately linked to the conduct of this fermen-
silage fermentation, fermentative yeasts grow to tati~n.~'OAmong other microorganisms, yeasts
populations of lo7cells per gram during the initial play a key role in the fermentation, developing
stages. Thereafter, their populations decrease, but to populations of lo6to lo* cells per gram during
remain significant (around lo5cells per gram) for the initial stages. A range of Kloeckera, Hun-
many months. It is considered that yeasts com- senula, Candida, Saccharomyces, and Pichia sp.
Pete with lactic acid bacteria for fermentable has been implicated in these fermentations, but
growth substrates but may nevertheless encour- a most desired species has not been identi-
age the growth of these bacteria by the production fied.230-232Pectinolytic species of yeasts are be-
of vitamins. However, exposure of fully fer- lieved to be involved in the fermentation of coffee
mented silage to air activates yeast growth and beans.z3oHowever, their impact on the quality
leads to rapid deterioration in product quality. of the final product appears minimal but never-

14
 theless worthy of more detailed investigation. tive alcoholic aroma and flavor, along with gas-
Fermented rice, cassava, maize, and vegetable siness. In addition, many hundreds of secondary
products have major significance in the diets of end products are formed, and these have a sig-
people in Asia and Africa, and recent studies nificant impact on sensory properties. Such prod-
suggest important roles of yeasts in contribut- ucts include higher alcohols, organic acids, es-
ing to the quality and acceptability of these ters, aldehydes, and ketogenic substances that,
foods .233-236 although produced in small concentrations, have
very low flavor and aroma t h r e ~ h o l d s .The ~~,~~~
production and sensory relevance of these sec-
ondary metabolites are well known for Sacch.
IV. GROWTH AND BIOCHEMICAL
cerevisiae because of the importance of this
ACTIVITIES OF YEASTS IN FOODS
species in the fermentation of alcoholic bever-
ages,’3,244-247 but unfortunately, not much is known
During their growth, yeasts utilize food con-
about their formation by other species. The re-
stitutents and generate metabolic end products.
views of Benda,204and later Lafon-Lafourcade205
As a consequence, the physical, chemical, and
on wine fermentation, and the book written by
sensory properties of the food are substantially
Margalith248refer to secondary metabolite pro-
changed. Generally, the nature of these changes
duction by species other than Sacch. cerevisiae,
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for any particular food is not well described,

but the available information is patchy and some-
making it difficult to explain spoilage on a bio-
times conflicting. Tables 3 and 4 are presented
chemical basis. Many factors affect the growth
as a guide to the literature on the production of
and biochemical activities of yeasts in foods. In
some alcohols, esters, acetic acid, and acetal-
broad terms, the main factors are the chemical dehyde by a range of species significant in food
composition of the food, the conditions of pro- and beverage spoilage. Most of these species do
cessing and storage, and the inherent properties not produce as much ethanol as Sacch. cerevis-
of the yeast species present. Many aspects of the iae, but some species, for example, K. apiculata,
growth and biochemical activities of yeasts in H . anomala, Zygosacch. bailii, Zygosacch.
relation to food spoilage have been reviewed and rouxii, Brettanomyces sp., and Candida sp. are
discussed by previous author^.^-^. 237-240 The fol- noted for their stronger production of secondary
lowing sections provide a more detailed and up-
metabolites such as acetic acid, ethyl acetate, and
dated discussion of these topics, highlighting, acetaldehyde. In high enough concentrations,
where appropriate, major gaps in existing knowl- these substances can have an overpowering effect
edge. on the sensory quality of the product. The con-
centrations of individual metabolites produced by
Sacch. cerevisiae are significantly influenced by
A. Utilization of Carbohydrate Sugars the strain of yeast and environmental factors such
as oxygen availability, temperature, and chemi-
Fermentation of sugars such as glucose, fruc- cal composition of the growth substrate. Such
tose, sucrose, and maltose is a key metabolic influences should also apply to other species of
reaction of most yeasts when cultured under fa- spoilage yeasts.
cultative anaerobic conditions. 241.242 Because Some species, especially those in the genera
sugars commonly occur in foods and beverages, Rhodotorula and Cryptococcus, and a few spe-
fermentation features significantly in the spoilage cies in Candida, Pichia, Hansenula, and De-
process. Lactose is fermented by only a few baryomyces, can only utilize sugars under aero-
species243(e.g., Kluy. marxianus, C. pseudotro- bic c ~ n d i t i o n s .Their
~ ~ ’ growth on the surface of
picalis) that become relevant in the spoilage of products is frequently obvious as film, powder,
dairy products. Principally, these sugars are con- or colonies, but nothing can be stated about the
verted to ethanol and carbon dioxide, causing the types of secondary end products they might pro-
product to lose sweetness and acquire a distinc- duce under these conditions.

15
 TABLE 3
Production of Alcohols by Several Species of Spoilage Yeast

lsoamyl 2-
Ethanol Propanol lsobutanol alcohol Phenvlethanol
Species ("/I (mg/l) (mg/l) (mg4 (ms4 Ref.

Saccharomyces cerevisiae 6-23 9-1 70 5-78 17-330 5-83 247,249-258

Kloeckera apiculata 5-6.5 16-32 4-38 4-17 21 -27 137,251,253,
254,256,257
Hanseniaspora uvarum 2.5-3 1-3 2-3 - 1.5-3.5 252,255
Candida krusei 1-6.5 1-23 38-1 06 22-1 00 - 251,254,256
Candida sfellata 4.5-6.5 4-8 13-21 - 6-1 1 137,255
Zygosaccharomyces bailii 5.5-1 2.5 10-34 12-57 59-1 40 13-22 255,256
Saccharomycodes ludwigii 8-1 7 5-42 22-1 38 50-63 15-87 252-255
Pichia membranaefaciens 0.1-0.5 <1 1-9 0.5-9.5 - 250,251,254,
256
Hansenula anomala 0.2-4.5 3-15 18-29 1 1 -25 27 250,252,254,
256
Metschnikowia 2 <1-43 37-1 23 21 -243 22 254
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pulcherrima
Schizosaccharomyces 2-14 1-15 3-22 5-40 13 249,251,253-
pombe 256

Note: See also References 204,205,and 248.

6. Metabolism of Nitrogen Compounds is caused by growth of B . intermedius and the

production of substituted tetrahydropyridines. The
Yeast metabolism of nitrogen compounds, formation of these substances appears to be con-
such as amino acids, amines, urea, purines, and nected to the metabolism of lysine.218.21y
pyrimidines, was reviewed by Large,261who in- Utilization of the curing agents sodium nitrite
dicated the fragmentary nature of knowledge on and sodium nitrate by some yeasts (e.g., D.hun-
this subject, Even less is known about any link senii and C. furnatu) has implications in the mi-
between the metabolism of these substances and crobiological stability and safety of processed
the generation of end products that could influ- meats. 16.52.77
ence the sensory quality of foods. However, it
is known from beer,246wine,202-205 and
fermentations that amino acid metabolism is C. Organic Acids
linked to the production of higher alcohols, al-
dehydes, and ketogenic end products (e.g., di- Yeasts can either produce or metabolize or-
acetyl) that can significantly impact on sensory ganic acid^,^^^,^^^ thereby changing the acidity
properties. Production of the aromatic alcohol, and flavor profile of the product. Succinic acid
phenylethyl alcohol, in wines is related to the is the main carboxylic acid produced by yeasts
metabolism of phenylalanine by Succh. cerevis- during fermentation and amounts up to 2 gfl may
iae,2hswhile in cheeses it is formed from this be formed; however, its impact upon product
amino acid by the activities of Kluy. marxianus quality seems rarely mentioned. More sensory
and D. hansenii.266Decarboxylation of amino significance is attached to acetic acid, which is
acids leads to the production of amines.264The the main volatile acid produced on sugar fer-
reports74on the production of volatile amines and mentation. As indicated in Table 4, there is a
ammonia by C. lipolytica during growth on sea- significant variation between species in the pro-
foods need follow-up study. As mentioned al- duction of this acid, but more careful comparative
ready, the development of mousy taints in wines studies are required. Moreover, environmental

16
 TABLE 4
Production of Acetic Acid, Esters, and Acetaldehyde by Several Species of Spoilage
Yeasts

Acetic acid Ethyl acetate lsoamylacetate Acetaldehyde

Species (9/1) (mg/l) (mg/l)
Saccharomyces cerevisiae 0.3-0.8 10-100 0.1-16 50-1 20 253-268
Kloeckera apiculata 1-2.5 25-375 0.4-5 6-40 253,254,256,
260
Hanseniaspora uvarum - 25-70 0.2-0.3 - 255
Candida krusei 1 .o 220-730 <o. 1 - 254,256,260
Candida stellata 1-1.3 7-25 0.1-0.4 - 255
Zygosaccharomycesbailii 0.3 23-53 0.1-0.5 - 255,256,260,
261
Saccharomycodesludwigii - 26-200 0.1-0.7 5-217 253,255
Pichia membranaefaciens 0.25 16-21 1-6 - 254,256,261
Hansenula anomala 1-2 137-21 50 1-1 1 - 254,256,259,
261
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Metschnikowia pulcherrima 0.1-0.1 5 150-382 0.1-0.8 23-40 254

Schizosaccharomyces 0.3 10-40 <0.1 5-160 253,254,256,
Pmbe 261
Information on acetic acid and ethyl acetate production by Zygosaccharomyces rouxii and Brettanomyces
sp. may be found in the referencesof Yong et al.262.2a3
and Verachtert et aI.,ls7respectively;see also References
204,205,248.

conditions will influence the concentration of of spoilage bacteria. As mentioned in previous

acetic acid produced by yeasts. Low temperatures sections, such reactions are important in fer-
and high sugar concentrations increase acetic acid mented dairy and vegetable products, and silages
~ ~it~ is. ~ ~ ~where lactic, acetic, and propionic acids may be
production by Sacch. c e r e v i ~ i a e ,but
not known how these factors affect its production metabolized by surface flora of Pichia, Candida,
by other species. Thus, acetic acid may be a Rhodotorula, Cryptococcus, and Debaryomyces
prominent product in the low-temperature spoil- sp. The acidity of fruit products could be reduced
age of fruit juices and fruit pulps. Less attention by the utilization of citric and malic acids. Some
has been given to the production of medium and yeast species can metabolize malic acid under
long chain volatile fatty acids by yeasts, although fermentativeconditions. While Sacch. cerevisiae
it is known that they may affect sensory quali- only partially ferments this acid, species of Schi-
ties. 13247 The production of hexanoic, octanoic, zosaccharomyces and Zygosacch. bailii can fer-
and decanoic acids by yeasts has gained recent ment it completely.267
interest because of the possible antimicrobial ac-
tion of these compounds and their ability to limit
yeast g r ~ w t h . ~ ~ ~ , ~ ~ ' D. Volatile Sulfur Compounds
Many yeast species oxidatively metabolize
organic acids via the tricarboxylic acid cycle.241 At concentrations above certain threshold values,
However, the kinetics of these reactions are very volatile sulfur compounds such as hydrogen sul-
much determined by the mechanisms for trans- fide, sulfur dioxide, dimethyl sulfide, and other
porting the acid into the cell and the influence of organic thiols have objectionable sensory char-
environmental factors upon this transport. 267*271 Although bacteria are significant in
Oxidative utilization of organic acids can appre- the putrefactive sulfurous spoilage of foods, al-
ciably decrease the acidity of products and in- most nothing is known about the ability of yeasts
crease their pH to values that allow the growth to cause such spoilage. However, it is well doc-

17
 umented in the brewing and wine literature that basidium pullulans, and Trichosporon cutaneum
some, but not all, strains of Sacch. cerevisiae were caseinolytic. They tested 68 strains of D.
can produce objectionable concentrations of hy- hansenii because of its association with food
drogen sulfide and sulfur dioxide, and that these spoilage and found only 4 strains to be proteo-
properties are linked to their metabolism of amino lytic. Several species of Candida, including the
acids and inorganic sulfur compounds in the spoilage species C . lipolytica, were proteolytic.
growth medium. 13.246.272.273 Sulfur dioxide pro- Subsequent surveys278-283 have demonstrated ex-
duction not only affects aroma and flavor, but it tracellular protease production by a range of spe-
also has antimicrobial and antioxidant properties cies in the genera Candida, Cryptococcus, Rho-
that can affect the microbiological stability and dotorula, Pichia, Hansenulu, and Metschnikowia,
color of Reports on the production with more specialized attention being given to
of volatile sulfur compounds by other yeasts are the activities produced by Cryp. a l b i d ~ sSac- ,~~~
scant. R a n k i t ~ e ’briefly
~ ~ noted hydrogen sulfide charomycopsis f i b u l i g e ~ a , *K~. ~apiculata,281
*~~~
production by unspecified strains within the gen- Candida ole^,^^^ Yarrowia (Candida) lipoly-
era Pichia, Hansenula, Debaryomyces, Candida, t i ~ a , ~Torulopsis
” magnoliea,282and C . albi-
Hanseniaspora, and Rhodotorula. None of these cans.286Most authors conclude that Sacch. cere-
strains produced more hydrogen sulfide than visiae does not produce extracellular proteases.
Sacch. cerevisiae, except Schizosaccharomyces report^*^^^**^ on the presence of proteases in the
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malidevorans, which was noted as a strong pro- culture filtrates of this yeast should be cautiously
ducer. For all the yeasts examined, greater hy- accepted because it is possible that the authors
drogen sulfide production occurred during growth were measuring intracellular activity released by
at 30°C than at 15°C. There are brief references autolysis.
to H . anomola as being a significant producer of Recent interest in yeast proteases has been
hydrogen sulfide. 13.248 In unpublished work, we stimulated by the prospects of using these en-
have not detected hydrogen sulfide production in zymes to remove protein hazes from beer and
several isolates each of K . apiculata, C . krusei, wine,280-283 rather than by their roles in spoilage.
C. valida, and C . pulcherrima. Under the same Eklund et al.70 suggested a role of proteolytic
test conditions, all isolates of C . colliculosa, H . yeasts in the spoilage of crab meat, while Fleet
anomala, Sacch. cerevisiae, and some strains of and Mian79correlated the predominance of Kluy.
C . stellata produced hydrogen sulfide. None of marxianus and C.difluens in diary products with
the non-Saccharomyces yeasts produced more their strong caseinolytic activity. The single re-
hydrogen sulfide than Sacch. cerevisiae. port of extracellular protease production by K .
apiculata is worthy of follow-up research be-
cause this is a common spoilage yeast. Reports
E. Degradation of Proteins on protease production by spoilage species of
Kluyveromyces and Debaryomyces are not con-
Microbial proteolysis is a key spoilage re- sistent and further examination of these yeasts is
action in foods. Initially, it leads to the devel- needed. Candida zeylanoides and Cryp. Lauren-
opment of bitter flavors, followed by the pro- tii, frequently associated with meats, appear not
duction of strong ammoniacal odors and to be p r ~ t e o l y t i cThere
. ~ ~ seems to be no mention
putrefaction. K a l i ~ z has
* ~ ~written a general re- of protease production by the spoilage species,
view on microbial proteases. Until recently, little Zygosacch. bailii and Zygosacch. rouxii.
attention was given to the production of extra- Special consideration must be given to the
cellular proteolytic enzymes by yeasts. Ahearn selection of methods for screening the presence
et al.277screened approximately 800 species of of extracellular proteases in yeasts.282Some of
yeasts and yeast-like fungi for the production of these enzymes will hydrolyze casein but not gel-
extracellular caseinolytic enzymes and found only atin or albumin.*77*2x” The pH of the medium may
20 to 25% of the cultures to be positive for this affect the result and false positive reactions due
activity. Nearly all the isolates of Kluyvero- to autolytic release of intracellular enzymes can
myces, Endomycopsis, Sporobolmyces, Aureo- occur in older culture^.^^^.^^^

18
 F. Degradation of Lipids comprehensively reviewed by several authors.302-
306 This interest has not been stimulated by any

Steadzx9has written an excellent review of concern about the role of amylolytic yeasts in
the role of microbial lipases in causing food spoil- food spoilage, but by the desire to produce ethanol
age. Enzymatic degradation of food lipids pro- and yeast biomass from starchy ~ u b s t r a t e ands~~
duces a range of free fatty acids that, depending to produce low-carbohydrate beers. 305 According
on the type of acid and its concentration, confer , ~ ~ ~ 150 yeast spe-
to McCann and B a r r ~ e t t about
characteristic off-flavors described as either ran- cies produce extracellular amylases. Most studies
cid, soapy, metallic, oxidized, or “cardboardy”. have focused on the amylases produced by
The degradation of phospholipids can change the Schwaniomyces occidentalis. Saccharomycopsis
structural organization of lipid components within fibuliger, Sacch. diastaticus, and, to a lesser ex-
foods. Although the metabolism of lipids by tent, species within Candida and pic hi^.^‘"-^^
yeasts, including their production of extracellular With the exception of Sacch. diastaticus, the
lipases, has been well r e v i e ~ e d ,there ~ ~ ~ amylases of spoilage yeasts have not been studied
~ ~ -has
been little consideration of the role of yeasts in in any detail. As previously noted, Sacch. dias-
causing lipolysis of foods. Lipolytic yeasts mostly taticus causes beer spoilage by fermentation of
occur in the genera Candida, Rhodotorula, and residual dextrins. It seems that Zygosacch. rouxii
Cryptococcus and have been implicated in the and D . hansenii do not produce extracellular
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breakdown of fats in dairy and meat prod- amylases but further studies are needed of more
ucts.6.7.38.70.79.82 Approximately 30%of the yeasts strains of these species as well as other spoilage
isolated from British fresh sausages and minced yeasts.303 Amylolytic yeasts are potentially sig-
beef were lipolytic. I 6 Candida l i p ~ l y t i c ais~an~ ~ nificant in the spoilage of cereal products and
exceptionally strong producer of extracellular li- those products (e.g., meat sausages, yogurts, fruit
pase that is able to degrade the fats in margar- pulp, salad dressing, sauces) where starch is used
ine,293,z94 lard,295,red meat,296 and olive as an ingredient. Ardhana and Fleet233have ob-
and soybean oils. 298 Other spoilage yeasts that served the growth of amylolytic yeasts in fer-
have been reported to produce extracellular lipase menting rice. The review of De discusses
activity are Cryp. a l b i d ~ sCryp. methods
, ~ ~ l~a ~ r e n t i i , ~ ~ . ~ ~ for determining amylase production by
C . z e ~ l a n o i d e sC, ~. f~~ m a t aC, .~r~~ g o s aC, .~ ~ yeasts.
d i f l u e n ~Kluy.
, ~ ~ m a r x i a l t ~ sand
, ~ ~species of the
yeast-like organism, T r i c h o s p ~ r o nHowever,
.~~
most of these reports require confirmation. At H. Degradation of Cellulose, Pectin, and
this stage, virtually nothing can be stated about Xylan
the biochemical characteristicsof the lipases pro-
duced by these species and how they operate in Microorganisms that produce extracellular
food systems. Because of the insolubility of lipids cellulases, pectinases, and xylanases are signif-
under aqueous conditions, methods for the study icant in initiating the spoilage of fruits and veg-
of microbial lipases are a little more complicated etables by breaking down the polysaccharides of
than usual, and this has probably deterred interest the skin. Only a few yeast species have been
in these enzymes. The reader is referred to the found to produce these enzymes. No yeasts have
reviews of Stead,289Ratledge and Tan,292and been reported to degrade cellulose, although spe-
Shelley et al.301for a discussion of methods for cies within the yeast-like fungi, Trichosporon,
studying microbial lipases. Aureobasdium, and Geotrichum possess this
p r ~ p e r t y . ~The
~ ~ following
-~’~ yeast species ex-
crete enzymes capable of degrading pectin: Kluy.
G. Degradation of Starch mar~ianus,~” C . kejj~r,~” C . f ~ r n a t a Cryp.
,~~~
a l b i d ~ sRhodotorula
,~~~ spp. ,314 and certain strains
Yeasts that have the ability to degrade starch of Sacch. c e r e ~ i s i a e as
, ~ ~well
~ as species of
have been the subject of many ecological, bio- Trichosporon and A ~ r e o b a s i d i u r n . ~ ’Th ~e. ~ ~ ~ ~ ~ ~ ~
chemical, and genetic studies in recent years, as few yeasts able to degrade xylan are Cryp. al-

19
 b i d u ~ ,Pichia
~ ' ~ ~ t i p i t i s ,and
~ ' ~species of Tricho- temperatures <O"C. 323 Davenport323focused at-
sporon and Aureobasidium. 3n7.3w Methods for tention on cold tolerant yeasts by collating reports
screening yeasts for the presence of these en- of species able to grow at low temperatures. His
zymes should take into consideration that enzyme data suggested that many yeasts probably grow
production may be constitutive, require the pres- much better at low temperatures than generally
ence of the polysaccharide substrate for induc- thought, and that many of the spoilage species
tion, be repressed by the presence of glucose, could be described as cold-tolerant or psychro-
and require the presence of glucose as well as trophic, i.e., able to grow well over the range 5"
the polysaccharide sub~trate.~"'~" .312~315 to 30°C. However, careful studies to determine
More careful examination of the yeasts as- the growth rates of spoilage yeasts at low tem-
sociated with spoiling fruits and vegetables will peratures and, more importantly, their minimum
probably reveal a greater incidence and signifi- temperatures for growth are lacking. A most
cance of polysaccharide degrading species than noteworthy study is that of Jermini and Schmidt-
presently thought. The spoilage of olives166.314 lor en^,^*^ who reported cardinal temperatures for
and sulfited strawberries"8,317by pectinolytic the growth of strains of Sacch. cerevisiae, Zyg-
yeasts is well documented. Pectinolytic yeasts osacch. bailii, Zygosacch. rouxii, and D . han-
appear to be very active in the fermentation of senii in a medium containing 10% glucose. All
cocoa and coffee bean^.^^^-^^^ It is likely that the of the strains grew at 4"C, except that of Zygo-
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soft rotting of onions by Kluy. marxianuss161.*62 sacch. bailii, which grew at 6.5"C. None of the
is connected to pectinase production by this spe- strains grew at 4°C when glucose concentration
cies. Finally, the spoilage of fruit juices by Sacch. in the medium was increased to 50% or higher.
cerevisiae needs reinterpretation in view of the At these high glucose concentrations, the mini-
recent report3I5that some strains of this species mum temperature for growth was in the range
produce extracellular polygalacturonase. 12"to 13°C forzygosacch. bailii and6.5" to 10°C
for the other yeasts. In other studies, the presence
of antioxidant~,~~' sodium bi~arbonate,~'~ and
1. Growth and Activities at Low in the medium has decreased the ability
Ternperatures of Sacch. cerevisiae to grow at 4°C.Thus, in a
food environment, there may be several inter-
As indicated in Section 111, foods stored un- active factors that will determine the minimum
der refrigerated or frozen conditions undergo temperature at which yeasts grow.
spoilage by yeasts. Thus, knowledge about the Temperature also affects the metabolic be-
growth and biochemical activities of yeasts at low havior and other properties of yeast,320and con-
temperatures becomes relevant in understanding sequently should affect the biochemistry of food
the spoilage process and in developing predictive spoilage. Presently, not much is known about the
strategies for spoilage control. The effects of tem- influences of low temperature on the metabolism
perature, in general, on the growth and properties of spoilage yeasts. Many studies in the wine lit-
of yeasts have been reviewed by Van erature have certainly shown that Sacch. cere-
U d e r ~ , ~and
~ ' Watson,322but these discussions visiae produces different concentrations of al-
serve only to illustrate what little information is cohols, esters, and organic acids when grown at
known about the behavior of yeasts at low tem- low temperatures (5" to 10°C) compared with
peratures, especially for yeasts other than Sacch. high temperatures (20" to 25°C).204*20'*258~328 The
cerevisiae. There is little doubt from the exam- tolerance of ethanol is a key property of yeasts
ples presented in Section I11 that many food- affected by temperature. 3277329Generally, ethanol
spoilage species (e.g., Sacch. cerevisiae, Zygo- toIerance is decreased at the extremes of high
sacch. bailii, Kl. apiculata, Kluy. marxianus, D . (>30"C) and low (-3°C) temperatures. The
hansenii, Candida sp.) grow very well in the ethanol tolerance of K1.apiculata, and C . stellata
temperature range 5" to 10°C. Some species (e.g., is significantly increased at 10°C compared with
C. zeylanoides, Cryp. laurentii, D. hansenii, 25" to 30°C,330thereby allowing these species to
Rhodotorula sp.) have been reported to grow at make a greater contribution to the ecology and

20
 biochemistry of fruit juice spoilage at lower tem- visiae are 50- to 150-fold higher than the D60”
peratures. 137 At the higher temperatures, these values for vegetative cells. 1 4 5 , 3 3 3 Asci-producing
species are quickly overgrown by the more cultures of Zygosacch. rouxii and Zygosacch.
ethanol-tolerant species of Sacch. cervisiae and bailii have D60” values, respectively, that are 20-
Zygosacch. bailii. Yeast metabolism of organic to 50-fold and 5- to 8-fold greater than those of
acids at low temperatures would be of particular vegetative cultures.343 Collectively, the findings
relevance in the spoilage and processing of dairy of these heat-resistance studies have important
products, and warrants examination. practical implications in designing treatments for
heat-processing products, such as fruit concen-
trates, soft drinks, and syrups, where sugar con-
J. Heat Inactivation centrations are high and preservatives and an-
tioxidants may or may not be present.
Outbreaks of yeast spoilage in heat-processed
soft drinks, fruit juices, fruit concentrates, syr-
ups, and beer have stimulated much interest in K. Growth in High Concentrations of
the susceptibilityhesistance of yeasts to heat de- Sugar and Salt
struction. 1 4 5 , 3 3 1 Thermal death curves and deci-
Yeasts that grow in environments containing
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mal reduction (D) values have now been pub-

lished for Sacch. c e r e v i ~ i a e , Zygosacch. ~~~-~~ high concentrations of sugar (50 to 60%) or salt
rouxii, 341.342 Zygosacch. bailii,33 1.333.337-339.343 H (10 to 20%) deserve special mention not only
anomala,331 , 3 3 6 , 3 3 7 , 3 3 9 3 4 D . ha n ~ e n i i , ’P~. ~ . ~ because
~~ they commonly spoil foods with these
m e r n b r a n a e f a ~ i e n s , ~ ~Kluy. ~ * ~ ~ ~rnarxi-
*~~~ properties, but also because they have interesting
anurs,145,332,336k,lapiculata,332,336 C . krusei,335-337,339 metabolic reactions. The best known examples
C . l a m b i ~ aB, .~a~n ~o r n a l ~ sand , ~ ~several
~ other of these species are Zygosacch. rouxii, Zygo-
species mentioned in these references. Under sacch. bailii, Zygosacch. bisporus, Schizosacch.
normal environmental conditions, the vegetative pornbe, Candida lactis-condensi, C . farnata, and
cells of these species are very quickly inactivated H . anomala which are frequently associated with
by temperatures of 60” to 65°C. The D60” values sugary environments, 172,346 and D . hansenii,
of Sacch. cerevisiae, Zygosacch. bailii, and Zyg- C . famata, C . polymorpha, Pichia farinosa, Pi-
osacch. rouxii, some of the more heat-resistant chia miso, and Zygosacch. rouxii, with respect
yeasts, are in the range of 0.1 to 0.4 min. How- to high salt environment.’76,346 Such species do
ever, for all yeasts, these D values are signifi- not have an obligate requirement for high con-
cantly influenced by environmental factors. They centrations of solutes, and they grow equally well
are decreased (i.e., the yeasts are more sensitive in environments of low sugar or low salt con-
to destruction) when the cells are healed in the centration. However, they are referred to as being
presence of preservatives (e.g., sodium ben- xero- or osmotolerant to distinguish them from
zoate, potassium sorbate, sulfur dioxide),334-339 other species, such as Sacch. cerevisiae, that can-
organic a ~ i d ~antioxidants,325 , ~ ~ ~ * ethan01,~”9~~*
~ ~ ~ not grow at these high concentrations. A distin-
and low pH.334*336,337 In contrast, yeast cells are guishing characteristic is their ability to grow in
much more resistant to inactivation when heated environments having water activity (Aw) values
in environments containing high concentrations <0.85. Aspects of the ecology and biochemistry
of sugars (30 to 60%) or salt.335*339,341-343*345 The of these yeasts have been reviewed by Tilbury,172
D60”values for Zygosacch. rouxii or Zygosacch. C ~ r r yand , ~ Onishi.176
~
bailii can increase from <O. 1 min in the presence Biochemical studies of xerotolerant yeasts
of 3% glucose to >2.5 to 10.0 minutes in the have focused on the mechanisms they adopt to
presence of 60% glucose, depending on the syn- grow under these extremes of solute concentra-
ergistic influence of other factors such as tion and external osmotic pressure. Much re-
PH.”~-”~ Yeasts that produce ascospores are more search, reviewed by O n i ~ h iand
’~~ has
heat resistant than nonascospore-forming yeasts. established convincingly that the tolerance of
The D60” values for ascospores of Sacch. cere- Zygosacch rouxii and D . hansenii to these ex-

21
 tremes is achieved by the synthesis and intracel- osacch. rouxii, Zygosacch. bisporus, C . krusei,
lular accumulation of glycerol to concentrations P . membranaefaciens, and Schizosacch.
that balance the osmotic pressure across the cell pornbe.182,356.357 Table 5 shows the minimum con-
membrane. In addition, other polyalcohols such centrations of several preservatives necessary to
as arabitol may be p r ~ d u c e d . ~ A~ *similar-~~~ inhibit the growth of a range of spoilage yeasts.
mechanism operates in H. an~rnala.~”Interest- The data clearly show Zygosacch. bailii to be the
ingly, Sacch. cerevisiae also produces high con- most preservative-resistant species - a fact well
centrations of glycerol in response to environ- accepted by most authors. 140*182,357 However, the
ments of low Aw, but is unable to retain this values presented in Table 5 should be taken as a
molecule within the cell, and it leaks into the guide only, and in the context of demonstrating
extracellular environment.348.352 This process is the diversity of resistance between yeast species.
energetically unfavorable, thereby restricting the Many environmental factors affect the minimum
ability of this species to tolerate environments of concentration of preservative needed to inhibit
very low Aw. yeast growth. Of these factors, pH is the most
The relevance of this discussion to food important. The inhibition of yeast growth by all
spoilage is that xerotolerant and nonxerotolerant the preservatives shown in Table 5 is significantly
yeasts respond to high salt or high sugar envi- enhanced at lower pH values (e.g., pH 3.0 to
ronments by producing very significant concen- 4.0), where a greater proportion of the acid or
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trations of polyols, and these would be expected sulfur dioxide is present as the undissociated
to impact on the sensory qualities of the product. form.357-359 It is the undissociated form of these
The type of polyol produced (e.g., glycerol, xy- molecules that is best able to enter the cell. Thus,
litol, arabitol, dulcitol, mannitol, etc.) depends at pH 3.0, the growth of Zygosacch. bailii is in-
on the species and environmental influences, and hibited by 1500 mg/l of sodium benzoate, where-
these topics are discussed in detail by O n i ~ h i ” ~ as at pH 4.8 a concentration of 4500 mg/l is
and Spencer and Spencer.353In the cases of Zyg- required for this i n h i b i t i ~ n . ’However,
~~ Cole and
osacch. rouxii and Zygosacch. bailii, ethanol is Keenan3@’ carefully point out that the concentra-
still a main end product of metabolism at high tion of the undissociated acid is not the sole factor
concentrations of glucose, but less is formed as and that there is also a synergistic interaction
some of the glucose is channeled into polyol pro- between pH and the preservative acid. The pres-
d ~ c t i o n . ” ~ .It~ ’would
~ be interesting to know ence of sugars and lowered water activity, as
how growth of yeasts in high salt or high sugar occurs in foods of high sugar concentration, may
environments affects their production of second- either increase or decrease yeast tolerance of the
ary metabolites (e.g., higher alcohols, esters, etc.) preservative, but further studies on these influ-
and their ability to metabolize organic acids. ences are needed to clarify discrepant observa-
tions. 3.58.359.361.362The presence of ethanol ampli-
fies the effect of sorbic acid on Zygosacch.
L. Preservatives and Antimicrobials bisporus and Sacch. c e r e v i ~ i a e The . ~ ~ ~type of
acid (e.g., citric, lactic, malic) naturally present
When permitted by food legislation, pre- in the food or added as an acidulant can also
servatives may be added to some foods and bev- affect yeast tolerance of preservatives. 258,3627364

erages to control yeast Foods so treated, There is now good evidence to show that some
however, are prone to spoilage by preservative- yeasts build up resistance through repeated ex-
resistant species, and this problem is consistently posure to the pre~ervative.~“’,~~’ Thus, adaptation
observed for products such as soft drinks, fruit of Sacch. cerevisiae to growth in the presence of
juices, fruit concentrates, syrups, salad dress- sodium benzoate increased its tolerance of this
ings, mayonnaise, tomato and other types of preservative from 100 to 175 mg/l and adaptation
sauces, and wines. 140.182.355 The main preserva- of Zygosacch. bailii increased its tolerance from
tives used are benzoic acid and its derivatives, 600 to 1300 mg/l.365Also of significance is the
sorbic acid, acetic acid, and sulfur dioxide. The report that ascospores may be more resistant to
main resistant yeasts are Zygosacch. bailii, Zyg- preservative action than vegetative cells. 366

22
 TABLE 5
Minimum Concentrations of Preservatives Required to Prevent the Growth of Some Spoilage
Yeasts”

Benzoic acid Sorbic acid Acetic acid Propionic acid Sulfur dioxide
Species (mg/l) (mgll) (s4 (9/1) (mg/l, (free)b

Zygosaccharomyces bailii 600 600 (1200) 25 15 200

Zygosaccharomyces rouxii 200 500 (1200) 9 3 -
Candida krusei 300 300 15 8 75
Pichia membranaefaciens 200 200 20 - -
Schizosaccharornyces pombe 300 600 16 10 125
Saccharomyces cerevisiae 100 200 10 6 75-1 00
Hansenula anomala 1 40 150 6 4 50-75
Kloeckera apiculata 125 200 6 3 7
Kluyveromyces marxianus 125 150 6 3 50
Rhodotorula rubra 100 <loo <1 - -
Breitanomyces intermedius 300 400 - - -

Concentrations measured at pH 3.5. The

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Data adapted from Warfh,357,36B.369Pitt,358E k l ~ n d and

, ~ ~King
~ et
values in parentheses are for cells adapted to growth in the presence of the preservative. See Restaino et
and Jerrnini and Schrnidt-Loren~~~~ for the effects of sorbic acid and benzoic acid on osmotolerant yeasts. Sac-
chammycodes ludwigii tolerate up to 200 mg/l of sulfur dioxide (free).368
Free sulfur dioxide represents the mixture of molecular sulfur dioxide and the bisulfite and sulfite anions.3m

E k l ~ n has
d ~ discussed
~~ the molecular mech- conditions it seems that they produce unusually
anisms by which sorbic and benzoic acids inhibit high concentrations of carbon dioxide.
yeasts, but information on this subject is not com- The use of sulfur dioxide as an antimicrobial
plete. Of special note is the work of Warth,368-371 agent is well r e ~ i e w e d , ~ but,
~ ~ ”surprisingly,
~’ its
who has attempted to explain why some yeasts action against yeasts is still very poorly under-
(e.g., Zygosacch. bailii) are more preservative- stood. Although Table 5 shows strains of Sac-
tolerant than others (e.g., Sacch. cerevisiae). On charomycodes ludwigii and Zygosucch. bailii
entering the cell, the undissociated acid disso- being among the most resistant to sulfur dioxide,
ciates into its anion and a proton because of the more comprehensive comparative studies are
somewhat neutral intracellular pH. Intracellular necessary. Pilkington and have noted a
accumulation of the anion and acidification due strain of Zygosacch. bailii that was more sensi-
to proton production eventually inhibit the met- tive to sulfur dioxide than Sacch. cerevisiue, and
abolic machinery of the cell. According to Heard and Fleet377noted some resistance in strains
Warth,357preservative-resistant species such as of K . apiculata. Assessing the antimicrobial ac-
Zygosacch. bailii have developed special trans- tivity of sulfur dioxie is complicated by the fact
port and pumping mechanisms for exporting the that in aqueous solution it forms sulfurous acid
anion and protons out of the cell, thereby pre- that dissociates into three forms, namely, mo-
venting their intracellular accumulation. More- lecular sulfur dioxide, sulfite, and bisulfite, the
over, they may have mechanisms that restrict proportions of which depend upon the pH.373-375
entry of the preservative into the ce11.370,371
These Molecular sulfur dioxide is the form that is an-
explanations, however, are not fully supported timicrobial because it readily enters the yeast cell,
by the observations of Cole and Keenan.372 but, at pH values above 4.0, the dissociation
There appears to be no information on the equilibrium is such that <1% occurs in this
types of secondary end products produced by form.373Moreover, the sulfite and bisulfite an-
yeasts when grown in the presence of sorbate or ions have a strong tendency to irreversibly bind
benzoate preservatives, although under these to any carbonyl compounds (e.g., sugars, acet-

23
 aldehyde) that may be present in the food, further dissolves in the aqueous phase of food systems
reducing the concentration of molecular sulfur for form carbonic acid and also readily dissolves
dioxide. Consequently, high concentrations of in organic components such as ethanol. The in-
total sulfur dioxie (>200 mg/l) must be added to fluence of carbon dioxide on microbial activity
foods to obtain sufficient molecular sulfur diox- in foods is complicated by food properties that
ide (e.g., 1 to 2 mg/l) that would have any an- affect its solubility as carbonic acid and the dis-
timicrobial benefit. Most foods to which sulfur sociation of carbonic acid into the bicarbonate
dioxide has been added would contain high con- and carbonate ions, and any effect of pressure
centrations of the sulfite anion,25and more con- buildup when this gas is produced in an enclosed
sideration needs to be given to any effect this system. Several recent review^^^*-^^^ focus atten-
form would have on yeasts. tion on the effects of carbon dioxide on micro-
By comparing the reactions of strains of organisms, including yeasts, but data are still
Sacch. cerevisiae, Saccharomycodes ludwigii, insufficient to draw specific conclusions. How-
and Zygosacch. bailii, Rose and c o - w o r k e r ~ ~ ~ ever,
~ * ~ ~some
~ general points can be presented. At
have attempted to explain why some yeasts are high pressures (>30 atm), the viability of yeast
more tolerant of sulfur dioxide than others. At cells is 1 0 ~ t ,and ~ at~ extremely
~ - ~ ~high ~ pressures
this stage, it appears that sulfur dioxide-tolerant (>5000 atm) the spoilage of fruit juices by yeasts
strains produce and excrete higher concentrations is prevented.386At much lower pressures (e.g.,
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of acetaldehyde (which binds the sulfite anion) 0.5 to 2 atm, as might be produced during food/
when they are cultured in the presence of sulfur beverage spoilage), the rate of yeast (Sacch. cere-
dioxide. This behavior also has been observed visiae) growth is reduced, and there can be sig-
for sulfite-resistant strains of Candida spp. iso- nificant effects upon the utilization of amino acids
lated from Overall, the molecular basis and production of secondary metabolites that af-
of sulfur dioxide action against yeast cells is very fect flavor The influence of car-
complex and poorly understood, and the reader bon dioxide upon yeast growth and metabolic
is directed to the discussions of Rose and behavior may vary with the yeast species. Ac-
Pilkington17' and Dillon and Board25for further cording to Ison and G~tteridge,~*'species of
details. However, it is relevant that when grow- Brettanomyces and Dekkera are more tolerant of
ing in the presence of sulfur dioxide, yeasts ex- higher concentrations of carbon dioxide (at pH
crete significant concentrations of acetaldehyde 3.65) than species such as Sacch. cerevisiae and
and this could affect the sensory properties of the Zygosacch. bailii, and this may account for their
product. greater predominance in the spoilage of some
The resistance of some yeasts (e.g., Zygo- carbonated beverages. Between pH 7.5 and 9.5,
sacch. bailii and P . membranaefaciens) to rela- most of the carbon dioxides exist as the bicar-
tively high concentrations of acetic acid (Table bonate ion, and there is some inconclusive evi-
5 ) is significant in products such as mayonnaise, dence suggesting that this anion can be inhibitory
salad dressings, and various sauces where this to yeast growth.326.389
acid is used as an acidulant and preserva-
tive. 17O.17Y.182.379 Other organic acids considered
useful in controlling yeast growth include pro- M. Lysis
pionic, citric, and lactic acids, but generally they
are less effective than acetic a ~ i d . ~ ' ~ . ~ ~ ~ The . ~ ~lysis
~ .of~ microbial
~ ~ cells and release of
The antagonistic effects of carbon dioxide on their intracellular constituents into the environ-
the growth, survival, and metabolic behavior of ment are rarely considered in the context of spoil-
yeasts demand more serious consideration than age. This lack of consideration is probably due
given in the past. Carbon dioxide is a major end to oversight rather than any assumption that cell
product of the growth of yeasts and other micro- lysis is not significant in the spoilage reaction.
organisms, but, because it is usually perceived The lysis of yeast cells in food/beverage envi-
as a gas that escapes to the environment, its in- ronments can be caused by two mechanisms: by
fluences are generally overlooked. However, it the action of exogenous enzymes that degrade

24
 the cell walls of the yeasts and by autolysis. Some as a significant reaction in the spoilage of foods
but not all commodities are spoiled by a mixed and beverages.
flora of microorganisms, including yeasts. Some
species within this flora could produce the ap-
propriate glucanase-type enzymes that hydrolyse V. ISOLATION, ENUMERATION, AND
the walls of yeasts.3goDuring the course of our IDENTIFICATION OF FOOD SPOILAGE
own unpublished studies, we have observed, YEASTS
microscopically, the presence of yeast cells in
the initial stages of spoilage of some fruits and The isolation, enumeration, and identifica-
cereal products. A day or two later, the presence tion of yeasts in foods involve the following op-
of yeast cells is not evident by microscopic ob- erations: (1) suspension of the food sample by
servation, and the cells have been replaced by homogenization in a suitable diluent; (2) dilution
bacteria. Clearly, the yeast cells have been lysed, of the suspension; (3) enumeration of the cell
presumably by enzymes produced by the suc- population in suspension by most probable num-
ceeding flora. The intracellular contents of lo6 ber, agar plating, membrane filtration, micro-
to 10' yeast cells per gram would be released into scopic or electronic techniques; (4)purification
the product, and must impact on its sensory of isolates; and (5) identification of isolates to
properties. generic and species level according to morpho-
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Autolysis occurs when yeast cells have com- logical, biochemical, and physiological proper-
pleted their growth. At this state, cellular organ- ties. Recent literature detailing the principles,
ization breaks down and the macromolecular con- practices, and problems associated with these op-
stituents of the cell are degraded by the action of erations has been reviewed by Fleet.9 Other key
endogenous proteases, lipases, nucleases, and reviews covering these topics are those of Fung
carbohydrases. The degraded products as well as and Liang,16" Mossel et al. ,397
the enzymes responsible are released into the sur- Koburger and Marth,398Pitt and Jar-
rounding environment. Although the chemical vis and Williams,400and King et a1." The fol-
changes that occur during yeast autolysis have lowing sections summarize the current status of
been studied by several authors, their description knowledge, emphasizing recent developments and
is still very incomplete, and the biochemical basis future research needs.
of the process remains poorly understood.391392
Moreover, the available knowledge about yeast
autolysis concerns only Sacch. cerevisiae and A. Isolation
nothing is known about the autolysis of other
species. Yeast autolysis is known to occur during 1. Diluents
wine202and champagne393fermentation and dur-
ing the maturation stage of beer A suitable diluent is required for preparation
where it causes significant increases in the con- of the food suspension and its subsequent dilution
centrations of free amino acids and free fatty before plating onto agar media. Little consider-
acids in these products. The flavor profile of the ation has been given to the selection of diluents
product is changed and, depending on the degree for the enumeration of yeasts. Examination of
of autolysis, this change may either contribute or the literature shows frequent use of distilled water,
detract from product quality. Excessive autolysis saline, phosphate buffer, peptone water, 10%su-
can spoil the flavor of the product and also pro- crose solution, and saline solutions containing
vide nutrients that encourage the growth of spoil- Tween 80. Unpublished results from the labo-
age bacteria. ratory of Mian and Fleet indicate significant de-
Yeast extracts and yeast autolysates are pow- creases in the viability of several spoilage yeasts
erful flavorants, a property well illustrated by the on dilution in either distilled water or saline. Vi-
fact that they are commercially prepared for use ability of the same species remained constant for
as flavor enhancers in the food industry.395Con- 2 h after dilution in 0.1% peptone solution, and
sequently, it is unrealistic to ignore yeast lysis this is the preferred general-use diluent in our

25
 laboratory. However, for isolation of yeasts from effective bacterial control, each antibiotic being
foods containing high sugar concentration, it is used at a final concentration of 100 mg/l. In our
necessary to add sucrose at a concentration 10% laboratory, malt extract agar containing oxyte-
or higher to the diluent to minimize the death tracycline and, if necessary, chloramphenicol is
and loss of cells by osmotic hock.'^*^^* Simi- used for general yeast isolation and enumeration.
larly, diluents containing added salt may benefit Other laboratories use oxytetracycline-glucose
the isolation of yeasts from high-salt foods. yeast extract agar397or chlortetracycline-chlor-
amphenicol plate count agar.398There appears to
be very little difference in the performance of
2. General Plating Media these and other media. The book edited by King
et al.@I contains contributions from several lab-
Agar plating is the most frequently used oratories where performances of the different me-
method for isolating and enumerating yeasts in dia have been compared. There is some indica-
foods, although direct microscopic examination, tion that gentamicin may inhibit the growth of
especially for foods that appear spoiled, should certain y e a s t ~ . ~ " . ~ ~ ~
not be discounted as a rapid, inexpensive method Overgrowth of isolation plates with molds
for assessing yeast presence and approximate cell can be a serious problem for some foods. Various
population. Both pour and spread plating tech- authors have incorporated either rose bengal,
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niques are used, but there is increasing evidence dichloran, sodium or potassium propionate, or
that spread plating gives more accurate and more diphenyl into isolation media to control this
reliable data.9*401 growth, but careful evaluation of the effects of
The ideal plating medium should have the these substances on yeast recovery has not been
following properties: (1) be nutritionally suffi- d ~ n e .Moreover,
~ . ~ ~ the potential for these sub-
cient to support the growth of all yeast species; stances to interact and reduce the effectiveness
(2) allow the recovery and growth of sublethally of bacterial antibiotics in the medium has not
injured yeast cells; (3) selectively suppress the been examined. An alternative approach for con-
growth of bacteria; and (4) restrict overgrowth trolling mold growth involves preincubation of
by molds. Frequently used media include potato inoculated plates under anaerobic conditions for
dextrose agar, malt extract agar, plate count agar 3 d, followed by 2 d of aerobic incubation.404
and glucose yeast extract agar.9.396.'97,400,401
Bac-
terial growth in these media is controlled either
by adjusting the pH to 3.5 or by incorporating 3. Selective-Differential Plating Media
bacterial antibiotics into the medium composi-
tion. Use of acidified (pH 3.5) media has de- Several authors have discussed the concept
clined in recent years because they give lower of using selective-differential media for the "tar-
yeast counts than media containing antibiotics .9 get" isolation and enumeration of particular yeast
Antibiotics used to control bacterial growth in species, but, compared with bacteria, this ap-
yeast media have been tabulated by Davenport396 proach is poorly developed. 83239*3967400 The most
and Jarvis and Williams,'"' and are oxytetracyc- comprehensive studies have been conducted n the
line, chlortetracycline, chloramphenicol, genta- b r e ~ i n g ' ~and
~-~' ~i ~n e ' " ' ~industries,
.~ where the
micin, and streptomycin. The antibiotic selected goal has been to develop media that selectively
should: (1) be active against a broad spectrum of differentiate between Sacch. cerevisiae, spoilage
bacteria; (2) be resistant to inactivation by other species within the genus Succharomyces, and
media components and food inocula; (3) be stable spoilage species in other genera. Thus, lysine
during incubation of the plating medium; and (4) agar is used to isolate non-Saccharomyces spe-
have no adverse effect on the recovery of yeasts. cies when they occur in conjunction with high
For foods that contain high populations of bac- populations of Sacch. cerevisiae, since the latter
teria (e.g., fresh meat, dairy, and vegetable prod- organism cannot utilize lysine as a nitrogen
ucts), it may be necessary to incorporate a mix- source. 1949405 Ethanol-tolerant yeasts may be iso-
ture of two antibiotics into the medium for lated in the presence of ethanol-sensitive species

26
 by plating onto a medium supplemented with Underestimation of injured yeast cells in pro-
ethan~l.~" Species (e.g., Zygosacch. bailii) re- cessed foods might be avoided by incubating the
sistant to preservatives, such as sodium benzoate food suspension in a repair medium before enu-
or potassium sorbate, can be selectively cultured meration by plating. This approach is well ac-
on media that incorporate these preservatives or cepted for the enumeration of bacterial cells,
acetic acid in their formulation.182,399 Xerotoler- where optimum conditions (e.g., medium com-
ant yeasts that dominate in foods of high sugar position, temperature, and time of incubation) for
concentration are specifically isolated on media the repair and resuscitation of injured cells have
containing 45 to 60% sucrose or sucrose plus been determined. However, practical conditions
glucose.'72,402 Kluyveromyces marxianus, a spe- for the repair of injured yeast cells have not been
cies that causes spoilage of dairy products, is established and warrant study.9
selectively cultured by exploiting its ability to
utilize lactose and grow at 45°C.239References
for the isolation of amylolytic, proteolytic, pec- B. Enumeration
tinolytic, and lipolytic yeasts were mentioned in
previous sections. The potential use of various Agar plating is the most common method
dyes in media for the selective isolation of food used to enumerate yeasts in foods. Other con-
spoilage yeasts is reported by Fung and Liang.I6" ventional methods often used are membrane fil-
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tration, most probable number, and microscopic

observations of stained or unstained prepara-
4. Sublethal Injury t i o n ~ . With
~ ~ ~the, ~exception of microscopic
techniques, which are relatively insensitive and
The performance of any isolation medium for tedious, these cultural methods generally require
yeasts should take into consideration the recovery 2 to 5 d of incubation before visible colonies are
of sublethally injured cells. Since most foods are formed and a result obtained. In many instances,
processed in some form, they are likely to harbor this time is too long for quality control manage-
a proportion of injured yeast cells that might not ment to take corrective action should unaccept-
grow on the medium chosen for isolation. This able contamination be detected. In recent years,
possibility is particularly relevant for media made there have been major advances in developing
selective by conditions such as decreased pH or methods for the rapid detection and enumeration
increased concentration of sugar or salt. Fleet9 of microorganisms, including yeasts. The most
has reviewed the literature on sublethal injury in promising methods are those based on the mea-
yeasts, but the reader is also referred to earlier, surement of electrical impedance, the measure-
more extensive discussions by Stevenson and ment of ATP, and examination by fluorescence
G r a ~ m l i c hBeuchat,408
,~~~ and several reviews in microscopy. The application of these methods to
King et a1.401Literature on the topic is scant and food spoilage yeasts is discussed in the following
unfocused, but the available data do show that sections. The reader is referred to Wood and
environmental stresses such as heating and freez- Gibb~,~'O Jarvis and E a ~ t e r , ~and
" Firstenberg-
ing cause sublethal injury in yeast cells, and that Eden and Z i n d ~ l u for
s ~ ~general
~ reviews of the
this injury is manifested by an inability of the principles and applications of these technologies.
cells to form colonies on nutritionally limiting or
selective media. Thus, heat-stressed cells of Zyg-
osacch. rouzii give 10- to 100-fold less counts 1. Electrical Impedance
on yeast extract-malt agar supplemented with 49%
glucose (Aw 0.880) than on unsupplemented me- As a consequence of growth, microorgan-
dium (Aw 0.998).409 Generally, more research is isms change the electrical properties (conduct-
needed to quantify the degree of injury suffered ance, capacitance, impedance) of their environ-
by yeast cells when exposed to various stresses ment. These changes are readily measured
and to determine the potential of such cells to electronically and two instruments, the Malthus
initiate spoilage. and the Bactometer, are commercially available

27
 for this purpose. The time to detect these changes with a sensitive photometer and optimum assay
is directly related to the initial population of mi- conditions, it seems possible to detect as few as
crobial cells, and it is this principle that is ex- 10 cells per milliliter within an assay time of
ploited in the microbiological analysis of foods. about 5 min. Research to date suggests that this
The technology offers the advantage of faster technology would have excellent potential for the
detection of microbial populations compared with very rapid detection of yeasts in beer,42’-424
plate counting, as well as the benefits of testing wine,208.425 carbonated beverage^,^" and culture
many samples simultaneously, automation, and media.427Where membrane filtration of the prod-
computer processing of data. Impedance tech- uct is possible (e.g., with beer, wine, and some
nology is now widely accepted in the food in- carbonated beverages), yeast cells from 1 to 2 1
dustry for monitoring the populations of both to- of sample could be concentrated on the mem-
tal and specific bacteria.412 brane, thereby extending the lower limit of de-
The application of impedance technology to tection to a few cells per liter. Despite the obvious
monitoring yeast populations in foods is at an attractions of simplicity, speed, and sensitivity
early stage of development. The main obstacle offered by this technology, it has not received
has been the development of suitable media that widespread acceptance by the food industries.
restrict the growth of bacteria, permit rapid growth Some obstacles to its acceptance have been in-
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of yeasts, and generate a good, reliable electrical terference from ATP of nonmicrobial origin,
signal, with little interference from the food sam- quenching of the bioluminescent reaction by food
ple. The formulations of several media that meet constituents, cost of reagents and instruments,
these requirements have been given and these and the fact that the data produced are nonspecific
offer prospects of detecting yeast contamination (i.e., the ATP measured comes from all bacteria,
of lo2 to lo3 cells per milliliter within 12 to 24 yeasts, and molds present in the sample). How-
h -413-416 Promising applications of impedance ever, many of these problems can be overcome,
technology for monitoring yeasts in orange juice but more rigorous evaluation of the technology
c~ncentrate,~”fruit mixes for yogurt produc- is needed to confirm its reliability and sensitivity
t i ~ n , ~wines,419
’* and beePo have been reported. for particular applications.
By incorporating ethanol into the formulation,
Henschke and Thomas4IYattempted to develop a
medium that selectively measured the presence 3. Fluorescence Microscopy
of wine spoilage yeasts. While a reliable elec-
trical signal was obtained with this medium, the Microscopic examination provides a direct,
rate of yeast growth was decreased and detection rapid means of estimating the presence of mi-
times of 2 to 3 d or longer were required to detect crobial contaminants in food samples. Objections
the presence of lo3 cells per milliliter for some to this method have included poor sensitivity
species. Attempts to develop a medium for the (populations of lo5 to lo6 cells per milliliter are
selective measurement of wild brewing yeasts necessary to observe any cells within a micro-
were not successful because the selective agent scope field), inability to distinguish between vi-
(copper sulfate) added to the formulation inter- able and nonviable cells, and the tedious nature
fered with the electrical of the work. In recent years several advances
have occurred that overcome such objections.
Membrane filtration of liquid samples or food
2. Measurement of ATP homogenates significantly improves the sensitiv-
ity of detection by concentrating the microbial
All viable microorganisms contain ATP. cells from larger volumes of the sample onto the
Measurement of ATP by bioluminescence tech- surface of the membrane. Subsequently, these
nology permits the detection and enumeration of membranes can be treated and stained for direct
microorganisms in a matter of minutes. There is examination under the microscope. Treatment of
a very good linear relationship between the con- food homogenates with a mixture of trypsin and
centration of ATP in yeast cells and colony counts; Tween 80 to dissolve and disperse particulate

28
 material significantly improves their filterability quires considerable expertise, and is further com-
so that larger sample volumes can be examined. plicated by many changes to the generic and spe-
Fluorogenic stains such as aniline Via- cific names of yeasts that have occurred over the
and tetrazolium derivatives430reliably years. The changes continue, as taxonomists
distinguish between viable and nonviable yeast search for better phylogenetic classifications.
cells, and dramatically facilitate cell detection Thus, key spoilage species such as Zygosacch.
and enumeration by fluorescence or epifluoresc- bailii and Zygosacch. rouxii were previously
ence microscopes linked to image analyzers and known as Sacch. bailii and Sacch. rouxii, re-
computers for data processing. When combined spectively. Kluyveromyces marxianus was pre-
into the so-called direct epifluorescent filter tech- viously described as Kluy. fragilis, Kluy. lactis,
nique (DEFT), these developments offer excel- Kluy. bulgaricus, Sacch. lactis, or Sacch. fra-
lent prospects for the rapid detection (within 30 gitis. Spoilage species once described in the ge-
min) of yeasts in beer, wine, and carbonated bev- nus Torulopsis are now described within Can-
e r a g e ~ . The
~ ~ main
~ . ~limitation
~~ of DEFT is its dida. A detailed discussion of these taxonomic
sensitivity, as it requires a minimum population changes is beyond the scope of this review and
of approximately lo3yeast cells per milliliter for the reader is referred to Deak and B e u ~ h a t 4for~~
a detection signal. However, it has the potential a more specific account.
to detect as little as 1 yeast cell per milliliter of The practical difficulties associated with
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beer or wine because of the ability to filter 1 1 identifying yeasts by conventional procedures
or more of these products. P e t t i ~ h e Phas
~ ~de- have led to the development of shortened iden-
scribed a 30-min DEFT procedure that detects tification schemes that are based on yeast re-
500 cells or more of osmophilic spoilage yeasts sponse to a few carefully selected tests, and min-
in creme fondant. By preincubating the sample iaturized diagnostic kits that are now
of creme fondant for 24 h prior to the application commercially available. Deak and B e ~ c h a t 4de- ~~
of DEFT, the procedure could detect an initial scribe an identification key, specific for food
contaminating load of 2 yeast cells per gram. spoilage yeasts, that is based on reactions to about
These short times of assay (30 mid24 h, de- 15 tests. They claim that it eliminates the need
pending on contamination level) represent a sub- for conducting about 80% of the conventional
stantial improvement over the 3 to 4 d required tests, and reliably identifies 215 species. How-
by conventional agar plating. The use of DEFT ever, a recent practical and theoretical evaluation
to measure yeast populations in foods and bev- of this simplified key has found it to be wanting
erages is still very limited and further research and unreliable.439Rodriguez440has described a
is needed on its application and reliability. simplified system for identifying wine spoilage
yeasts, based on the growth of isolates on lysine
agar, pantothenate-free agar, and two other me-
C. Yeast Identification dia containing either cycloheximide or 5% so-
dium chloride.
Yeasts are classified into genera and species Fung and Liar@" have published a detailed
on the basis of their morphological, physiologi- study on the use of selective dyes and 23 key
cal, biochemical, and, more recently, genetic tests for accelerated and convenient identification
proper tie^.^^^,^^^ They are identified by conduct- of yeasts isolated from meat products. A com-
ing the tests and following the classification puter program was used to assist interpretation
schemes described in Kreger-~an-Rij~~' and Bar- of the data. The general utility and reliability of
nett et al.436Lin and Fung437give a more detailed this interesting system needs confirmation by
critical assessment of some of these tests. Gen- studies in other laboratories.
erally, it is necessary to conduct some 50 to 100 Several ready-to-use diagnostic kits have been
tests to reliably identify most yeasts to species developed for the rapid identification of clinically
level. Consequently, the work load is demanding significant yeast species. 16a,437,44' Generally, they
and 1 to 2 weeks are required to obtain results. exploit yeast response to a very limited range of
Moreover, accurate interpretation of the data re- carbon and nitrogen assimilation compounds and

29
 give results within 48 h. Computer-assisted inter- assay (ELISA) for Brettanornyces sp. that causes
pretation of the data is available for some kits. wine ~poilage.~"
In our experience,&* these kits offer too few tests
to permit unequivocal identification of food and
beverage yeasts. and Ison4& have VI. FURTHER RESEARCH
shown that the APISOCH system, which tests the
assimilation of 49 carbohydrate substrates, could Gaps in existing knowledge and specific re-
be adapted to assist yeast identification. While search needs for spoilage yeasts have been men-
the data from these galleries seem reliable, they tioned in different sections of this review. In sum-
must be supplemented with the results of addi- mary, future research should aim to:
tional tests (e .g., nitrogen assimilation) to enable
unequivocal yeast identification. We have de- 1. Provide a stronger quantitative knowledge
veloped a system that enables all of the fermen- of the occurrence and growth of yeasts in
tation and assimilation tests (both carbon and ni- specific commodities and to identify to spe-
trogen substrates) listed in K r e g e r - ~ a n - R iand
j~~~ cies level the main yeasts present
Barnett et al.436 to be done in the wells of a 2. Examine the ecological interrelationships
microtiter tray.442Data are available within 48 between yeasts, bacteria, and molds during
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h. Moreover, vitamin growth tests, other growth spoilage of products

tests, and sporulation tests can be conducted in 3. Determine the biochemical and physiolog-
the wells. Eighteen reference yeast species were ical properties of spoilage yeasts other than
reliably identified by this system. When data from Sacch. cerevisiae and to examine the influ-
the trays are processed using the computer pro- ence of environmental factors upon the bio-
gram of Barnett et al. (Barnett, Payne, and Yar- chemical reactions of these yeasts in foods
row, Yeast Identification: PC Program-Version 4. Develop the use of impedimetric, biolu-
2, August 1990), a most convenient and rapid minescene, and fluorescence microscopy
system for identifying yeasts is obtained. methods for the rapid enumeration of yeasts
As mentioned in the section on alcoholic bev- 5 . Develop gene probe and ELISA techniques
erages, it is now important to distinguish between for the rapid detection of key spoilage yeasts
strains of yeasts within the one species. Several
molecular techniques have been investigated for
this purpose, of which chromosome electropho-
resis and DNA fingerprinting by restriction nu-
clease degradation are the most promising .445 Both
wine strains and brewing strains of Sacch. cere-
1. Hurley, R., de Louvois, J., and Mulhall, A., Yeasts
visiae are readily differentiated by either of these
as human and animal pathogens, in The Yeasts, Vol.
techniques .445-48 Other methods hat show good 1 , 2nd ed., Rose, A. H. and Harrison, J. S . , Eds.,
prospects of distinguishing between strains within Academic Press, London, 1987, 207.
the one species as well as between strains of 2. Todd, E. C., Foodborne disease in Canada - a 5
different species are based on the electrophoretic year summary, 1.Food Protect., 46, 650, 1983.
3 . Adverse Reactions to Foods, NIH, Publ. No. 114-
analysis of protein^‘'‘'^ and chromatographic pro-
2442. American Academy of Allergy and Immunol-
files of fatty acids comprising cell lipids.450-452 ogy Committee on Adverse Reactions to Foods, Na-
However, both of these methods require a strong tional Institute of Allergy and Infectious Diseases,
degree of control and standardization because the U.S. Department of Health and Human Services,
protein and lipid composition of yeasts vary with Washington, D.C., 1984.
culture conditions and age. 4. Crook, W. G., The Yeast Connection: A Medical
Breakthrough, 3rd ed., Professional Books, Nash-
Enzyme immunoassay and gene probe tech- ville, TN, 1986.
nologies have not yet been developed for the 5 . Mrak, E. M. and Phaff, H. F., Yeasts, Annu. Rev.
rapid analysis of spoilage yeasts, although there Microbial., 2 , I , 1948.
is one report of an enzyme-linked immunosorbent 6. Ingram, M., Yeasts in food spoilage, in The Chem-

30
 istry and Biology of Yeasts, Cook. A. H . , Ed., Ac- various types of vacuum packages and length of stor-
ademic Press, New York, 1958, 603. age on the microbial flora of wholesale and retail cuts
7. Walker, H. W. and Ayres, J. C., Yeasts as spoilage of beef, J . Milk Food Technol., 39, 745, 1976.
organisms, in The Yeasts, Vol. 3, Yeast Technology, 22. Vanderzant, C., Hanna, M. O., Ehlers, J. H.,
Rose, A. H. and Harrison, J. S . , Eds., Academic SaveU, J. W., Smith, G. C., Griffin, D. B., TerreU,
Press, London, 1970, 463. R. N., Lind, K. O., and Galloway, D. E., Cen-
8. Peppier, H. J., Yeasts, in FoodMicrobiology: Pub- tralized packaging of beef loin steaks with different
lic Health and Spoilage Aspects, De Figueiredo, M. P. oxygen-barrier films: microbiological characteristics,
and Splittstoesser, D. F., Eds., AVI Publishing, J . Food Sci., 47, 1070, 1982.
Westport, CT, 1976, 427. 23. Vanderzant, C., Chesser, L. K., Savell, J. W.,
9. Fleet, G. H., Food spoilage yeasts, in Yeast Tech- Gardner, F. A., and Smith, G. C., Effect of ad-
nology, Spencer, J. F. T. and Spencer, D. M., Eds., dition of glucose, citrate and citrate-lactic acid on
Springer-Verlag, Berlin, 1990, 124.. microbiology and sensory characteristics of steaks
10. Fleet, G. H., Yeasts in dairy products: a review, J . from normal and dark, firm and dry, beef carcasses
Appl. Bacteriol., 68, 199, 1990. displayed in polyvinyl chloride film and in vacuum
11. Beveridge, E. C., The microbial spoilage of phar- packages, J . Food Protect., 46, 775, 1983.
maceutical products, in Microbial Aspects of rhe De- 24. Ali, S. H., Hoshsyare, D. F., and At-Delaimy,
terioration of Materials, Gilbert, R. J. and Lovelock, K. S., Microbial counts on surfaces of lamb, J . Food
D. W., Eds., Academic Press, London, 1975, 213. Protect., 45, 1013, 1982.
12. Baird, R. M., Drugs and cosmetics, in Microbial 25. Dillon, V. M. and Board, R. G., A study of sulfite-
Deterioration, Economic Microbiology, Vol. 6, Rose, tolerant yeasts from comminuted lamb products, Bio-
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

A. H., Ed., Academic Press, London, 1981, 387. tech. Appl. Biochem., 12, 99, 1990.
13. Berry, D. R. and Watson, D. C., Production of 26. Patterson, J. T. and Gibbs, P. A., Some micro-
organoleptic compounds, in Yeast Biotechnology, biological considerations applying to the condition-
Berry, D. R., Russell, I . , and Stewart, G. G . , Eds., ing, ageing and vacuum packaging of lamb, J . Food
Allen & Unwin, London, 1987, 345. Technol., 13, 1, 1978.
14. McMeekm, T. A., Microbial spoilage of meats, Dev. 27. Blickstad, E. and Molin, G., Carbon dioxide as a
FoodMicrobiol., 1, 1, 1982. controller of the spoilage flora of pork with special
15. Jay, J. J., Meats, poultry and seafoods, in Foodand reference to temperature and sodium chloride, 1.Food
Beverage Mycology, 2nd ed., Beuchat, L. R., Ed., Protect., 46, 756, 1983.
AVI PublishingNan Nostrand Reinhold, New York, 28. Blickstad, E. and Molin, G., The microbial flora
1987, 155. of smoked pork loin and frankfurter sausage stored
16. Dalton, H. K., Board, R. G., and Davenport, in different gas atmospheres at 4"C, J . Appl. Bac-
R. R., The yeasts of British fresh sausage and minced terol., 54, 45, 1983.
beef, J . Microbiol. Serol., Antonie van Leeuwen- 29. McMeekin, T. A. and Thomas, C. J., Aspects of
hoek; 50, 227, 1984. the microbial ecology of poultry processing and stor-
16a. Fung, D. Y. C. and Liang, C., Critical review of age: a review, Food Technol. Aust., 31, 35, 1979.
isolation, detection and identification of yeasts from 30. Barnes, E. M., Impey, C. S., Geeson, J. D., and
meat products, Crit. Rev. Food Sci. Nutr., 29, 341, Buhagiar, R. W. M., The effect of storage tem-
1990. perature on the shelf-life of eviscerated air-chilled
17. Aboukheir, S. and Kilbertus, G., Frequence des turkeys, Br. Poult. Sci., 191, 77, 1978.
levures dans les denrks alimentaires 5 base de viande, 31. Oblinger, J. L., Kennedy, J. E., McDonald, E. D.,
Ann. Nutr. Aliment., 28, 539, 1974. and West, R. O., Microbiological analysis of alli-
18. Beyer, K. and Sinell, H. J., Psychrotrophic micro- gator (Alligator mississippiensis) meat, J . Food Pro-
organisms in vacuum packaged chilled beef trim- tect., 44, 98, 1981.
mings, in Psychrotrophic Microorganisms in Spoil- 32. Hanna, M. O., Smith, G. C., Savell, J. W., Keith,
age and Pathogeniciry, Roberts, T. A., Hobbs, G., F. K., and Vanderzant, C., Microbial flora of liv-
Christian, J. H. B . , and Skovgaard, N . , Eds., Ac- ers, kidneys and hearts from beef, pork and lamb:
ademic Press, London, 1981, 191. effects of refrigeration, freezing and thawing, J . Food
19. Newsome, R. L., Langlois, B. E., Moody, W. G., Protect., 45, 63, 1982.
Gay, N., and Fox, J. D., Effect of time and method 33. Rothenberg, C. A., Berry, B. W., and Oblinger,
of ageing on the composition of the microflora of J. L., Microbiological characteristics of beef tongues
beef loins and corresponding steaks, J . Food Pro- and livers as affected by temperature-abuse and pack-
tect., 47, 114, 1984. aging systems, J . Food Protect., 45, 52, 1982.
20. Simard, R. E., Zee, J., and L'Heureux, L., Mi- 34. Visser, I. J. R., Koolmees, P. A., and Bijker,
crobial growth in carcasses and boxed beef during P. G. H., Microbiological conditions and keeping
storage, J . Food Protect., 47, 773, 1984. quality of veal tongues as affected by lactic acid de-
21. Seidman, S. C., Vanderzart, C., Hanna, M. O., contamination and vacuum packaging, J . Food Pro-
Carpenter, L. L., and Smith, G. C., Effect of tect., 51, 208, 1988.

31
 35. Shoup, J. G. and Oblinger, J. L., Microbiological packaging atmospheres, temperature and duration of
evaluation of retail ground beef: centralized and tra- storage on microbial changes, J. Food Sci., 49, 827,
ditional preparation, J. Milk Foud Technol., 39, 179, 1984.
1976. 50. Nielsen, H. J. S., Composition of bacterial flora in
36. Jay, J. M. and Margitic, S., Incidence of yeasts in sliced vacuum packaged bologna-type sausage as
fresh ground beef and their rations to bacteria, J. influenced by nitrate, J. Food Technol.. 18, 573,
Food Sci., 46, 648, 1981. 1983.
37. Hsieh, D. Y. and Jay, J. M., Characterization and 51. Grazia, L., Suzzi, G., Romano, P., and Giu-
identification of yeasts from fresh and spoiled ground dici, P., The yeasts in meat products, Yeasts, 5, S495,
beef, Int. J. Food Microbiol., 3 , 141, 1984. 1989.
38. Johannsen, E., Niemand, J. G., Eagle, L., and 52. Gardner, G. A., Microbiological and chemical
Bradenhann, G., Yeast flora of non-radurised and changes in lean wiltshire bacon during aerobic stor-
radurised mince beef - a taxonomic study, Int. J. age, J. Appl. Bacteriol., 34, 645, 1971.
Food Microbiol., 4, 217, 1984. 53. Sward, R. E., Lee, B. H., Laley, C. L., and
39. Dijkmann, K. E., Merits and shortcoming of DG18, Holley, R. A., Effects of temperature, light and stor-
OGY, OGGY and DRBC media for the examination age time on the microflora of vacuum or nitrogen-
of raw meats, in Methods for the Mycological Ex- packed frankfurters, J. Food Protect., 46, 199, 1983.
amination of Food, King, A. D.,Pin, J. l . , Beuchat, 54. Baldock, J. D., Frank, P. R., Graham, P. P., and
L. R., and Cony, J. E. L., U s . , Plenum Press, New h e y , F. J., Potassium sorbate as a fungistatic agent
York, 1986, 120. in country cured ham processing, J . Food Protect.,
40. Nychas, G. J. and Aikoudelos, J. S., Microbiol- 42, 780, 1979.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

ogical and physiochemical changes in minced meats 55. Draughon, F. A., Melton, C. C., and Maxe-
under carbon dioxide, nitrogen or air at 3"C, Inr. J . don, D., Microbial profiles of country cured hams
Food Sci. Technol., 25, 389, 1990. aged in stockinettes, barrier bags and paraffin wax,
41. Lowry, P. D. and Gill, C. O., Development of yeast Appl. Envzron. Microbiol., 41, 1078, 1981.
microflora on frozen lamb stored at - 5"C, J. Food 56. Kernp, J. D., Langlois, B. E., and Fox, J. D.,
Protect., 47, 309, 1984. Effects of vacuum packaging and potassium sorbate
42. Shay, B. J., Grau, F. H., Ford, A. L., Egan, on yield, yeast and mould growth and quality of dry-
A. F., and Ratcliff, D., Microbiological quality and cured hams, J. Food Sci., 46, 1015, 1981.
storage life of vacuum-packaged small goods, Food 57. Kernp, J. D., Langlois, B. E., and Fox, J. D.,
Technol. Aust.. 30, 48, 1978. Effect of potassium sorbate and vacuum packaging
43. Oblinger, J. L. and Kennedy, J. E., Microbiol- on the quality and microflora of dry-cured intact and
ogical evaluation of selected delicatessen meats from boneless hams, 1.Food Sci., 48, 1709, 1983.
retail supermarkets, J . Food Prorecr., 43, 530, 1980. 58. Kemp, J . D., Langlois, B. E., Fox, J. D., and
44. Tiwari, N. P. and Kadis, V. W., Microbiological Nicastro, F., Quality of dry-cured hams produced
quality of some delicatessan meat products, J. Food from pre-frozen hams as affected by mechanical ten-
Protect., 44,821, 1981. derization and vacuum packaging, J. Food Protect.,
45. Liestner, L. and Bern, Z., Vorkommen und Be- 49, 417, 1986.
deutung von Hefen bei Pokelfleischwaren, Fleis- 59. Halls, N. A., Aitken, K. H. R., and Henry, D.,
chwrrtschuf, 3, 350, 1970. The aerobic microflora of Scotch haggis, J. Food
46. Blickstad, E., Influence of water activity on micro- Technol.. 15, 111, 1980.
bial development in minced, cured pork, in relation 60. Liepe, H. U., Starter cultures in meat production, in
to gas headspace composition, Food Microbiol., 1, Biotechnology, Vol. 5, Food and Feed Produc.tion
177, 1984. with Microorganisms, Reed, G . , Ed., Verlag Chemie,
47. Blickstad, E. and Molin, G., Carbon dioxide as a Weinheim, 1983, 399.
controller of the spoilage flora of pork with special 61. Lucke, F. K., Fermented sausages, in Microbiology
reference to temperature and sodium chloride, J . Food of Fermented Foods, Vol. 2, Wood, B. J . B., Ed.,
Protect., 46, 756, 1893. Elsevier Applied Science, London, 1985, 41.
48. Lee, B. H., Simard, R. E., Laleye, C. L., and 62. Hagler, A. N. and Ahearn, D. G., Ecology of aquatic
Holley, R. A., Shelf-life of meat loaves packaged in yeasts, in The Yeasts, Vol. 1, 2nd ed., Biology of
vacuum or nitrogen gas. I. Effect of storage temper- Yeasts, Rose, A. H. and Harrison, J. S., Eds., Ac-
ature, light and time on the microflora change, J . ademic Press, London, 1987, 181.
Food Protect.. 47, 128, 1984. 63. Phaff, H. J., Mrak, E. M., and Williams, 0. B.,
49. Laleye, L. C., Lee, B. H . , Simard, R . E., Yeasts isolated from shrimp, Mycologia, 44, 432,
Carmichael, L., and Holley, R. A., Shelf-life of 1952.
vacuum- or nitrogen-packed pastrami: effects of 64.Koburger, J. A., Norden, A. R., and Kernpler,

32
 G. M., The microbial flora of rock shrimps - Si- 80. Subramanian, P. and Shankar, P. A., Commen-
cyonia brevirostris, J . Milk Food Technol., 38, 747, salistic interaction between Lactobacillus acidiophi-
1975. lus and lactose-fermenting yeasts in the preparation
65. Pagnocca, F. G., Mendonca-Hagler, L. C., and of acidilophilus-yeast milk, Cultured Dairy Prod. J . ,
Hagler, A. N., Yeasts associated with the white 20, 19, 1985.
shrimp Penaeus schmitti, and water of Septiba Bay, 81. Jordano, R., Medina, L. M., and Linares, M. J.,
Rio De Janeiro, Brasil, Yeasts, 5, S479, 1989. Occurrence of Torulopsis candida in fermented milk
66. Ross, S. S. and Morris, E. O., An investigation of containing bifidobacteria, in Les Laits Ferment&,
the yeast flora of marine fish from Scottish coastal Actualite de la Recherche, John Libbey Eurotext,
waters and a fishing ground off Ireland, J . Appl. Paris, 1989, 269.
Bacteriol., 28, 224, 1965. 82. Garrisson, E. R., Lipolytic yeasts in cream from
67. Roth, F. J., Ahearn, D. G., Fell, J. W., Meyers, dairy farms, J. Dairy Sci., 42, 905, 1959.
S. P., and Meyers, S. A., Ecology and taxonomy 83. Thomas, S. B., Psychrotrophic organisms in market
of yeasts isolated from various marine substrates, cream: a review. 11, Dairy Ind., 36, 145, 1971.
Limnol. Oceanogr., 7, 178, 1962. 84. Thomas, S. B., Psychrotrophic organisms in butter:
68. Bruce, J. and Morris, E. O., Psychrophilic yeasts a review. I, Dairy Id., 35, 79, 1970.
isolated from marine fish, Antonie van Leeuwenhoek; 85. Davis, J. G., The microbiology of yogurt, in Lactic
J . Microbiol. Serol., 39, 331, 1973. Acid Bacteria in Beverages and Food, Cam, J. G . ,
69. Chung, Y. M. and Lee, J. S., Inhibition of micro- Cutting, C. V., and Whiting, G. C., Eds., Academic
bial growth in English sole (Parephrys retulus), J. Press, London, 1975, 245.
Food Protect., 44, 66, 1981. 86. Suriyarachchi, V. R. and Fleet, G. H., Occurrence
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

70. Eklund, M. W., Spinelli, J., Miyauchi, D., and and growth of yeasts in yogurts, Appl. Environ. Mi-
Groninger, H., Characteristics of yeasts isolated from crobiol., 42, 574, 1981.
Pacific crab meat, Appl. Environ. Microbiol., 13, 87. Green, M. D. and Ibe, S. N., Yeasts as primary
985, 1965. contaminants in yogurts produced commercially in
71. Eklund, M. W., Spinelli, J., Miyauchi, D., and Lagos, Nigeria, J. Food Protect., 50, 193, 1987.
Dassow, J., Development of yeast on irradiated Pa- 88. Rohm, H., Lecher, F., and Lehner, M., Micro-
cific crab meat, J. Food Sci., 31, 424, 1965. flora of Austrian natural-set yogurt, J . Food Protect.,
72. Buck, J. D., Bubucis, P. M., and Combs, T. J., 53, 478, 1990.
Occurrence of human-associated yeasts in bivalve 89. Williams, A. P., A comparison of DRBC, OGY and
shellfish from Long Island Sound, Appl. Environ. RBC media for the enumeration of yeasts and molds
Microbiol., 33, 370, 1977. in foods, in Methods for the Mycological Examina-
73. Hood, M. A., Effects of harvesting waters and stor- tion of Food, King, A. D., Pitt, J. I., Beuchat, L.
age conditions on yeast populations in shellfish, J. R., and Corry, J. E. L., Eds., Plenum Press, New
Food Protect., 46, 105, 1983. York 1986, 89.
74. Kobatake, M., Tonogai, Y., and Ito, Y., Time 90. Devoyod, J. J., Yeasts in cheesemaking, in Yeast
courses for viable counts, pH and total volatile basic Technology, Spencer, F. J. and Spencer, D. M., Eds.,
nitrogen in squid homogenates (Ommastraphes bar- Springer-Verlag, Berlin, 1990, 228.
trami) inoculated with spoilage yeast or bacteria, J. 91. Gripon, J. C., Mould-ripened cheese, in Cheese:
Food Protect., 51, 971, 1988. Chemistry, Physics and Microbiology, Vol. 2, Fox,
75. Ayres, J. C., Temperature relationships and some P. F., Ed., Elsevier, London, 1987, 121.
characteristics of the microflora developing on re- 92. Ikemiya, M. and Yasumi, K., A strain of Debar-
frigerated beef, Food Res., 25, 1, 1960. yomyces hansenii isolated from processed cheese, J .
76. Walker, H. W. and Ayres, J. C., Characteristics Ferment. Technol., 51, 761, 1973.
of yeasts isolated from processed poultry and the 93. Horwood, J. F., Stark, W., and Hull, R. R., A
influence of tetracyclines on their growth, Appl. Mi- fermented, yeasty flavour defect in cheddar cheese,
crobiol., 7, 251, 1959. Aust. J. Dairy Technol., 42, 25, 1987.
77. Drake, S. D., Evans, J., and Niven, C. F., The 94. Romano, P., Grazia, L., Suzzi, G., and Gui-
identity of yeasts in the surface flora of packaged dici, P., The yeasts in cheesemaking, Yeast, S,(Spec.
frankfurters, Food Res., 24, 243, 1959. Iss.), S151, 1989.
78. Marth, E. H., Dairy products, in Food and Beverage 95. Guiraud, J. and Galzy, P., R81e d'une levure dans
Mycology, 2nd ed., Beuchat, L. R., Ed., AVI h b - un accident de fabrication chez des fromages h pAte
lishing/Van Nostrand Reinhold, New York, 1987, fraiche, Le Lait, 56, 495, 1976.
175. 96. Brocklehurst, T. F. and Lund, B. M., Microbiol-
79. Fleet, G. H. and Mian, M. A., The occurrence and ogical changes in cottage cheese varieties during stor-
growth of yeasts in dairy products, Int. J. Food Mi- age at +7"C, Food Microbiol., 2, 207, 1985.
crobiol., 4, 145, 1987. 97. Engel, V. G., Vorkommen vo Hefen in Frischkse

33
 - organoleptische Beeinflussung, Milchwissen- Vol. 1 , Rose, A. H. and Harrison, J. S., Eds., Ac-
schuft, 41, 692, 1986. ademic Press, London, 1969, 183.
98. Ghoniem, N. A., Incidence of yeasts other than Can- 116. Phaff, H. J. and Starmer, W. T., Yeasts associated
didu species in Damietta cheese, Milchwissenschuft, with plants, insects and soil, in The Yeasts, Vol. 1,
23, 482, 1968. 2nd ed., Rose, A. H. and Harrison, J. S., Eds.,
99. De Boek, E. and Kuik, D., A survey of the micro- Academic Press, London, 1987, 123.
biological quality of blue-veined cheese, Neth. Milk 117. Martini, A. and Martini, A. V., Grape must fer-
Duiry Technol., 41, 227, 1987. mentations: past and present, in Yeast Technology,
100. Nooitgedagt, A. J. and Hartog, B. J., A survey of Spencer, J. F. T. andspencer, D. M., Eds., Springer-
the microbiological quality of Brie and Camembert Verlag, Berlin, 1990, 105.
cheese, Nerh. Milk Dairy Technol.. 42, 56, 1988. 118. Dennis, C. and Buhagiar, R. W. M., Yeast spoil-
101. Galzin, M., Galzy, P., and Bret, G., Etude de la age of fresh and processed fruit and vegetables, in
flore de levure dans le fromage de Foquefort, Le Lait, Biology andActivities of Yeusts, Skinner, F. A., Pass-
50, I , 1970. more, S. M., and Davenport, R. R., Eds., Academic
102. Schmidt, J. L. and Lenior, J., Contribution ? l’6tude
i Press, London, 1980, 123.
de la flore levure du fromage de Camembert. Son 119. Lowings, P. H., The fungal contamination of Ken-
evolution au cours de la maturation, Le Lait, 58, 355, tish strawberry fruits in 1955, Appl. Microbiol., 4,
1978. 84, 1956.
103. Schmidt, J. L. and Lenoir, J., Contribution B I’6tude 120. De Camargo, R. and Phaff, H. J., Yeasts occurring
de flore levure du fromage de Camembert 11, Le Lait, in Drosophilia flies and in fermenting tomato fruits
60, 272, 1980. in Northern California, Food Res., 22, 367, 1957.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

104. Nunez, M., Medina, M., Gaya, P., and Dras- 121. Miller, M. W. and Phaff, H. J., Successive mi-
Amado, C., Les levures et les moisissures dans le crobial populations of calimyrna figs, Appl. Micro-
fromage bleu de Cabarales, Le Lait, 61, 62, 1981. biol., 10, 394, 1962.
105. Olson, N. F., Ripened Semisoft Cheeses, Pfizer 122. Vacek, D. C., Starmer, W. T., and Heed, W. B.,
Cheese Monographs, Vol. 4, Pfizer, New York, 1969. Relevance of the ecology of Citrus yeasts to the diet
106. Tzanetakis, N., Litopoulou-Tzanetaki, E., and of Drosophila, Microb. Ecol.. 5 , 43, 1979.
Manolkidis, K., Microbiology of Kopanisti, a tra- 123. Robbs, P. G., Hagler, A. N., and Mendonca-
ditional Greek cheese, FoodMicrobiol., 4,25 1, 1987. Hagler, L. C., Yeasts associated with a pineapple
107. Vergeade, J., Guirand, J., Larpent, J. P., and plantation in Rio de Janeiro, Brazil, Yeast, 5(Spec.
Galzy, P., Etude de la flore de levure de Saint-Nec- Iss.), S485, 1989.
taire, Le h i t , 56, 275, 1976. 124. Guerzoni, E. and Marchetti, R., Analysis of yeast
108. Lenoir, J., the surface flora and its role in the rip- flora associated with grape sour rot and of the chem-
ening of cheese, Int. J. Dairy Fed. Bull., 171, 3, ical disease markers, Appl. Environ. Microbiol., 5 3 ,
1984. 571, 1987.
109. Engel, G., Yeasts in silage and raw milk, Milchwis- 125. Golden, D. A., Heaton, E. K., and Beuchat, L. R.,
senschaf, 41, 633, 1986. Effect of chemical treatments on microbiological,
110. Tilbury, R. H., Davis, J. G., French, E. F., sensory and physical qualities of individually shrink-
Campbell-Lent, K., and Orbell, C., Taxonomy of wrapped produce, J. Food Protecr., SO, 673, 1987.
yeasts in yogurts and other dairy products, in 4th Int. 126. Roberts, R. G., Postharvest biological control of
Symp. on Yeasts, Klaushofer, H. and Sleyter, V. B., gray mould of apply by Cryptococcus luurentii, Phy-
Eds., Hochschulerschaft an der Hochschule fur Bod- toparhology, 80, 562, 1990.
enkultur, Vienna, 1974, 265. 127. Droby, S., Chalutz, E., Wilson, C. L . , and
111. Dennis, C., Post-harvest spoilage of fruits and veg- Wisniewski, M., Characterization of the biocontrol
etables, in Water, Fungi and Plunts, Ayres, P. G. activity of Deburyomyces hansenii in the control of
and Boddy, L., Eds., Cambridge University Press, Pencilliurn digitutum on grapefruit, Can. J. Micro-
Cambridge, 1986, 343. biol., 3 5 , 794, 1989.
112. Dennis, C., Post-Harvest Pathology of Fruits and 128. McLaughlin, R. J., Wisniewski, M. E., Wilson,
Vegetables, Academic Press, London, 1983. C. L., and Chalutz, E., Effect of inoculum con-
113. Salunkhe, D. K. and Desai, B. B., Eds., Post- centration and salt solutions on biological control of
harvest Biotechnology of Fruits, Vol. 1 and 2, CRC postharvest diseases of apple with Candida sp., Phy-
Press, Boca Raton, FL, 1984. topathology, 80, 456, 1990.
114. Lund, A., Ecology of yeasts, in The Chemistry and 129. Berry, J. M., Yeast problems in the food and bev-
Biology cf Yeasts, Cook. A. H., Ed., Academic Press, erage industry, in Food Mycology, Rhodes, M. E.,
New York, 1958, 63. Ed., G. F. Hall, Boston, 1979, 82.
115. Last, F. T. and Price, P., Yeasts associated with 130. Baird-Parker, A. C. and Kooiman, W. J., Soft
living plants and their environments, in The Yeasts, drinks, fruit juices, concentrates and fruit preserves,
 in Microbial Ecology of Foods, Vol. 2, Food Com- D. L., Aciduric and heat resistant microorganisms in
modities, Academic Press, London, 1980, 643. apple juice and cider processing operations, J . Food
13 1. Batchelor, V. J., Further microbiology of soft drinks, Sci., 50, 336, 1985.
in Developments in Soft Drinks Technology, Vol. 3, 147. Deak, T., Tabajdi-Pinter, V., and Fabri, I., Base-
Houghton, H. W., Ed., Elsevier, London, 1984,167. line counts on yeasts in soft drinks, in Methods for
132. Splittstoesser, D. F., Fruits and fruit products, in the Mycological Examination of Food, King, A. D.,
Food and Beverage Mycology, 2nd ed., Beuchat, L. Pitt, J. I., Beuchat, L. R., and Cony, J. E. C., Eds.,
R., Ed., Van Nostrand Reinhold, New York, 1987, Plenum Press, New York, 1986, 188.
101. 148. Put, H. M. C., De Jong, J., Sand, F. E. M. J.,
133. Beech, F. W. and Davenport, R. R., The role of and Van Grinsven, A. M., Heat resistance studies
yeasts in cider-making, in The Yeasts, Vol. 3, Rose, on yeast spp causing spoilage of soft drinks, J. Appl.
A. H. and Harrison, J. S., Eds., Academic Press, Bacteriol., 40, 135, 1976.
London, 1970, 73. 149. Pit, J. I., Unacceptable levels of specific fungi, in
134. Doores, S., The microbiology of apples and apple Methods for the Mycological Examination of Food,
products, Crit. Rev,FoodSci. Nutr., 19, 133, 1983. King, A. D., Pitt, J. I., Beuchat, L. R., and Cony,
135. Fleet, G. H., Lafon-Lafourcade, S., and Ribkreau- J. E. C., Eds., Plenum Press, New York, 1986, 212.
Gayon, P., Evolution of yeasts and lactic acid bac- 150. Parish, M. E. and Higgins, D. P., Yeasts and moulds
teria during fermentation and storage of Bordeau isolated from spoiling citrus products and by-prod-
wines, Appl. Environ. Microbiol., 48, 1034, 1984. ucts, J. Food Protect., 52, 261, 1989.
136. Lawrence, N. L., Wilson, D. C., and Pederson, 151. Parish, M. E. and Higgins, D. P., Investigation of
C. S., The growth of yeasts in grape juice stored at the microbial ecology of commercial grapefruit sec-
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

low temperatures. The types of yeasts and their growth tions, J. Food Protect., 53, 685, 1990.
in pure culture, Appl. Microbiol., 7, 7, 1959. 152. Brackett, R. E., Vegetables and related products,
137. Heard, G. M. and Fleet, G. H., The effects of in Food and Beverage Mycology, 2nd ed., Beuchat,
temperature and pH on the growth of yeast species L. R., Ed., Van Nostrand Reinhold, New York, 1987,
during the fermentation of grape juice, J. Appl. Bac- 129.
teriol., 65, 1988. 153. King, A. D., Michener, H. D., Bayne, H. G., and
138. Pederson, C. S., Albury, M. N., and Christensen, Mihara, K. L., Microbial studies on the shelf life
M. D., The growth of yeasts in grape juice stored at of cabbage and coleslaw, Appl. Environ, Microbiol.,
low temperature. IV. Fugistatic effects of organic 31, 404, 1976.
acids, Appl. Microbiol., 9, 162, 1961. 154. Geeson, J. D., The fungal and bacterial flora of
139. Splittstoesser, D. R. and Mattick, L. R., The stor- stored white cabbage, J. Appl. Bacteriol., 46, 189,
age life of refrigerated grape juice containing various 1979.
levels of sulfur dioxide, Am. J. Enol. Vitic., 32, 171, 155. Riser, E. C., Grabowski, J., and Glen, E. P.,
1981. Microbiology of hydroponically grown lettuce, J.
140. Thomas, D. S. and Davenport, R. R., Zygosac- Food Protect., 47, 765, 1984.
charomyces bailii - a profile of characteristics and 156. Horn, B. J., Association of Candida guilliermondii
spoilage activities, Food Microbiol., 2, 157, 1985. with amylolytic filamentous fungi on preharvest corn,
141. Sand, F. E. M. J., Spoilage of fountain syrup by Can. J. Microbiol., 31, 19, 1985.
Saccharomyces bailii, Brauwelt, 117, 238, 1977. 157. Koek, P. C., de Witte, Y., and de Maakes, J.,
142. Kitchell, R. L. and Miller, M. W., The viability The microbial ecology of prepared raw vegetables,in
of a yeast in high density orange juice concentrates Food Microbiology: Advances and Prospects, Rob-
stored at various temperatures, Food Technol., 14, erts, T. A. and Skinner, F. A., Eds., Academic Press,
547, 1960. London, 1983, 231.
143. Murdock, D. J. and Hatcher, W. S., Effect of 158. Garg, N., Churey, J. J., and Splittstoesser, D. F.,
temperature on survival of yeast in 45” and 65” Brix Effect of processing conditions on the microflora of
orange concentrate., J. Food Protect., 41,689, 1978. fresh-cut vegetables, J. Food Protect., 53,701, 1990.
144. Juven, B. J., Fate of spoilage microorganisms in 159. Beckers, H. J., Baseline counts of yeasts and molds
frozen and chilled tomato juices, J. Food Protect., in foods in The Netherlands, in Methods for the My-
42, 19, 1979. cological Examination of Food, King, A . D., Pitt,
145. Put, H. M. C. and De Jong, J., The heat resistance J. I., Beuchat, L. R., and Cony, J. E. C., Eds.,
of selected yeasts causing spoilage of canned soft Plenum Press, New York, 1986, 179.
drinks and fruit products, in Biology and Activities 160. Carlin, F., Nguyen-The, C., Chambroy, Y., and
of Yeasts, Skinner, F. A., Passmore, S. M., and Reich, M., Effects of controlled atmospheres on mi-
Davenport, R. R., Eds., Academic Press, London, crobial spoilage, electrolyte leakage and sugar con-
1980, 181. tent of fresh “ready to use” grated carrots, Int. J.
146. Swanson, K. M. J., Leasor, S. B., and Downing, Food Sci. Technol., 25, 110, 1990.

35
 161. Johnson, D. A., Rogers, J. D., and Regner, K. M., 178. International Commission on Microbiological Spec-
A soft rot of onion caused by yeast Kluyveromyces ifications for Foods, Fats and Oils, in Microbial Ecol-
mrixanus var. marxianus, Plant Dis.. 72, 359, 1988. ogy of Foods, Vol. 2 , Food Commodities, Academic
162. Johnson, D. A., Regner, K. M., and Lunden, J. D., Press, London, 1980, chap. 25.
Yeast soft rot of onion in the Walla Walla Valley of 179. Smittle, R. B., Microbiology of mayonnaise and
Washington and Oregon, Plant Dis., 73, 686, 1989. salad dressing: a review, J. Food Protect., 40, 415,
163. Collins, M. A. and Buick, R. K., Effect of tem- 1977.
perature on the spoilage of stored peas by Rhodoto- 180. Kurtzman, C. P., Rogers, R., and Hesseltine,
rulu glutinis, Food Microbiol., 6, 135, 1989. C. W., Microbiological spoilage of mayonnaise and
164. Brackett, R. E., Influence of modified atmosphere salad dressings, Appl. Environ. Microhiol., 21, 870,
packaging on the microflora and quality of fresh bell 1971.
peppers, J. Food Protect., 53, 255, 1990. 181. Smittle, R. B. and Flowers, R. S., Acid tolerant
165. Fleming, H. P., Fermented vegetables, in Fermented microorganisms involved in the spoilage of salad
Foods, Rose, A. H. and Harrison, J. S., Eds., Ac- dressings, J. Food Protect., 45, 977, 1982.
ademic Press, London, 1982, 228. 182. Pitt, J. I. and Hocking, A. D., Problems with pre-
166. Vaughn, R. H., Stevenson, K. E., Dave, B. A., servative resistant yeasts, Microbiol. Aliment. Nutr. ~

and Park, H.C., Fermenting yeasts associated with 6, 19, 1988.

softening and gas-pocket formation in olives, Appl. 183. Flores, L. M.,Palomar, L. S., Roh, P. A., and
Microbiol., 23, 316, 1972. Bullerman, L. B., Effect of potassium sorbate and
167. Christiansen, L. N. and King, N. S., The microbial other treatments on the microbial content and keeping
content of some salads and sandwiches of retail out- quality of a restaurant-type, Mexican hot sauce, J.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

lets, J. Milk Food Technol., 34, 289, 1971. Food Protect., 51, 4, 1988.
168. Fowler, J. L. and Clark, W. S., Microbiology of 184. Seiler, D. A. L., Yeast spoilage of bakery products,
delicatessen salads, J. Milk Food Technol., 38, 146, in Biology and Activities of Yeasts, Skinner, F. A , ,
1975. Passmore, S. M., and Davenport, R. R.. Eds., Ac-
169. Brocklehurst, T. F., White, C. A., and Dennis, ademic Press, London, 1980, 135.
C., The microflora of stored coleslaw and factors 185. Ponte, J. G. and Tsen, C. C., Bakery products, in
affecting the growth of spoilage yeasts in coleslaw, Food and Beverage Mycology, 2nd ed., Beuchat, L.
J. Appl. Bacteriol., 55, 57, 1983. R., Ed., Van Nostrand Reinhold, New York, 1987,
170. Brocklehurst, T. F. and Lund, B. M., Microbiol- 233.
ogical changes in mayonnaise-based salads during 186. Jackel, N., Natural breads may cause microbiolog-
storage, Food Microbiol., 1, 5 , 1984. ical problems, Bakery. September, 138, 1980.
171. Lindroth, S. E., Korkeala, H. J., Suihko, M. K., 187. Hesseltine, C. W., Graves, R. R., Rogers, R., and
Aalto, M. J., Kuhmonen, A. A., and Penttila, Burmeister, H. R., Aerobic and facultative micro-
P. L., Microbiological and sensory quality changes flora of fresh and spoiled refrigerated dough products,
in cabbage casserole and mixed vegetable salads with Appl. Microbiol., 18, 848, 1969.
mayonnaise during storage, J. Food Protect., 48, 188. Swartzentruber, A., Schwab, A. H., Wentz, B. A.,
292, 1985., Duran, A. P., and Reed, R. B., Microbiological
172. Tilbury, R. H., Xerotolerant (osmophilic) yeasts, in quality of biscuit dough, snack cakes and soyprotein
Biology andActivities of Yeasts, Skinner, F. A., Pass- meat extender, J . Food Protect., 47, 467, 1984.
more, S. M., and Davenport, R. R., Eds., Academic 189. Smith, J. P., Ooraikul, B., Kaersen, W. J., van
Press, London, 1980, 153. de Voort, F. R., Jackson, E. D., and Lawrence,
173. Tokuoka, K., Ishitania, T., Goto, S., and R. A., Shelf-life extension of a bakery product using
Komagata, K., Identification of yeasts isolated from ethanol vapour, Food Mirrobiol., 4, 329, 1987.
high-sugar foods, J. Gen. Appl. Microbiol.. 3 I , 4 1 I , 190. Spicher, G., Baked goods, in Biotechnology, Vol.
1985. 5, Food and Feed Production with Microorganisms,
174. Jermini, M. F. G., Geiges, O., and Schmidt- Reed, G., Ed., Verlag Chemie, Weinheim, 1983, 1 .
Lorenz, W. M., Detection isolation and identifica- 191. Lonner, C., Welander, T. Molin, N., Dostalek, M.,
tion of osmotolerant yeasts from high-sugar products, and Blockstad, E., The microflora of sour dough
J. Food Protect., 50, 468, 1987. started spontaneously on typical Swedish rye meal,
175. Restaino, L., Bills, S., Tscherneff, K., and Food Microbiol., 3, 3, 1986.
Lenovich, K. L., Growth characteristics of Saccha- 192. Okagbue, R. N., A note on the leavening activity
romyces rouxii isolated from chocolate syrup, Appl. of yeasts isolated from Nigerian palm wine, J. Appl.
Environ. Microbiol., 54, 1614, 1983. Bacteriol., 64, 235, 1990.
176. Onishi, H., Yeasts in fermented foods, in Yeast 193. Rainbow, C., Beer spoilage microorganisms, in
Technology, Spencer, J. F. T. and Spencer, D. M.. Brewing Science, Vol. 2, Pollock, J. R. A., Ed.,
Eds., Springer-Verlag, Berlin, 1990, 167. Academic Press, London, 1981, 491.
177. Adams,. M.R., Fermented fresh foods, Prog. Ind. 194. Ingledew, W. M. and Casey, G. P., The use and
Microbiol., 23, 159, 1986. understanding of media used in brewing mycology.

36
 I. Media for wild yeast. 11. Media for mouldskapid 21 1. Vos, P. J. A. and Gray, R. S., the origin control
methods, Brew. Dig., 57(March), 18(April),22, 1982. of H,S during fermentation of grape must, Am. J.
195. Campbell, I., Wild yeasts in brewing and distilling, Enol. Vitic., 30, 187, 1979.
in Brewing Microbiology, Priest, F. G . and Camp- 212. Rupela, 0. P. and Tauro, P., Isolation and char-
bell, I., Eds., Elsevier, London, 1987, 187. acterization of low hydrogen sulphide producing wine
196. Day, A. and Meylling, J. C., Practical experience yeast, Enzyme Microb. Technol., 6, 419, 1984.
with rapid methods for detecting yeasts in breweries, 213. Romano, P. and Suzzi, G., Le schiume persistenti
J. Inst. Brew., 89, 204, 1983. durante la fermentazione dei mosti, Vignevini, 14,
197. Verachtert, H., Kumara, S., and Dawond, E., 63, 1987.
Yeasts in mixed cultures, with emphasis on Iambic 214. Suzzi, G. and Romano, P., Characteristics of high
beer brewing, in Yeast, Biotechnology and Bioca- foam producing strains of Saccharomyces, Ann. Mi-
talysis, Verachtert, H. and DeMot, R., Eds., Marcel crobiol., 28, 127, 1978.
Dekker, New York, 1990, 429. 215. Heard, G. M. and Fleet, G. H., Occurrence and
198. Johnston, J. R., Brewing and distilling yeasts, in growth of yeast species during fermentation of some
Yeast Technology, Spencer, J. F. T., and Spencer, Australian wines, Food Technol. Aust., 38,22, 1986.
D. M., Eds., Springer-Verlag, Berlin, 1990, 55. 216. Heard, G. M. and Fleet, G. H., Occurrence and
199. Hammond, J. R. M. and Eckersley, K. W., Fer- growth of killer yeasts during wine fermentation, Appl.
mentation properties of brewing yeast with killer Environ. Microbiol., 53, 2171, 1987.
character, J. Inst. Brew., 90, 167, 1984. 217. Radler, F., Schmitt, M. J., and Meyer, B., Killer
200. Young, T. W., Killer yeasts, in The Yeasts, Vol. 2, toxin of Hanseniaspora uvarum, Arch. Microbiol.,
2nd ed., Rose, A. H. and Harrison, J. S., Eds., 154, 175, 1990.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

Academic Press, London, 1987, 131. 2 18. Heresztyn, T., Formation of substituted tetrahydro-
201. Novellie, L. and de Schaepdrijver, P., Modern de- pyridines by species of Brettanomyces and Lacto-
velopments in traditional African beers, Prog. Ind. bacillus isolated from mousy wines, Am. J. Enol.
Microbiol., 23, 73, 1986. Vitic., 37, 127, 1986.
202. Kunkee, R. E. and Amerine, M. A., Yeasts in 219. Heresztyn, T., Metabolism of volatile phenolic com-
winemaking, in The Yeasts, Vol. 3, Rose, A. H. and pounds from hydroxycinnamic acids by Brettano-
Harrison, J. S., Eds., Academic Press, London, 1970, myces yeast, Arch. Microbiol,, 146, 96, 1986.
5. 220. Flannigan, B., The microflora of barley and malt,
203. Kunkee, R. E. and Goswell, R. W., Tables wines, in Brewing Microbiology, Priest, F. G . and Camp-
in EconomicMicrobiology, Vol. 1, Rose, A. H., Ed., bell, I., Eds., Elsevier, London, 1987, 83.
Academic Press, London, 1977, 315. 221. Middelhoven, W. J. and van Baalen, A. H. M.,
204. Benda, I., Wine and brandy, in Prescott and Dunn’s Development of the yeast flora of whole-crop maize
IndustrialMicrobiology, 4th ed., Reed, G., Ed., AVI during ensiling and during subsequent aerobiosis, J.
Publishing, Westport, CT, 1982, 293. Sci. Food Agric., 42, 199, 1988.
205. Lafon-Lafourcade, S., Wine and brandy, in Bio- 222. Christensen, C. M., Field and storage fungi, in Food
technology, Vol. 5 , Food and Food Production with and Beverage Mycology, Beuchat, L. R., Ed., Van
Microorganisms, Reed, G., Ed., Verlag Chemie, Nostrand Reinhold, New York, 1987, 21 1.
Weinheim, 1983, 81. 223. Ayerst, G., Water and the ecology of fungi in stored
206. Fleet, G. H., Which species really conducts the fer- products, in Water Fungi and Plants, Ayres, P. G .
mentation, in Proc. 7th Australian Wine Industry and Boddy, L., Eds., Cambridge University Press,
Technical Conference, Williams, P. J., Davidson, Cambridge, 1986, 359.
D. M., and Lee, T. H., Eds., The Australian Wine 224. Peters, H. I., Flannigan, B., and Austin, B., Quan-
Research Institute, Urrbrae, 1990, 153. titative and qualitative studies of the microflora of
207. De-ak, T. and Reichart, O., Unacceptable levels of barley malt production, J. Appl. Bacteriol., 65, 279,
yeasts in bottled wine, in Methods for the Mycol- 1988.
ogical Examination offood, King, A. D., Pitt, J. I., 225. Douglas, P. E. and Flannigan, B., A microbiol-
Beuchat, L. R., and Cony, J. E. L., Eds., Plenum ogical evaluation of barley malt production, J. Inst.
Press, New York, 1986, 215. Brew., 94, 85, 1988.
208. Thomas, S. and Ackerman, J. C., A selective me- 226. Woolford, M. K., The silage fermentation, in Mi-
dium for detecting yeasts capable of spoiling wine, crobiology of Fermented Foods, Vol. 2, Wood, B.
J. Appl. Bacteriol., 65, 299, 1988. J. B., Ed., Elsevier, London, 1985, 85.
209. Reed, G. and Nagodawithana, T. W., Technology 227. Middelhoven, W. J. and Frazen, M. M., The yeast
of yeast usage in winemaking, Am. J. Enol. Vitic., flora of ensiled whole-crop maize, J. Sci. Food Agric.,
39, 83, 1988. 37, 885, 1986.
210. Kunkee, R. E., Selection and modification of yeasts 228. Middelhoven, W. J., de Jong, T. M., and de
and lactic acid bacteria for wine fermentation, Food Winter, M., Yeasts and fungi occurring in ensiled
Microbiol., 1, 315, 1984. whole-crop maize and other ensiled vegetable crops,

37
 Antonie van Leeuwenhoek; J. Microbiol. Serol., 57, 246. MacDonald, J., Reeve, P. T. V., Ruddlesden,
153, 1990. J. D., and White, F. H., Current approaches to
229. Moon, N. J. and Ely, L. O., Identification and brewery fermentations, in Progress in Industrial Mi-
properties of yeasts associated with the deterioration crobiology, Vol. 19, Modern Applications of Tra-
of wheat and alfalfa silages, Mycopathologia, 69, ditional Biotechnologies, Bushell, M. E., Ed., El-
153, 1979. sevier, Amsterdam, 1984.
230. Jones, K. L. and Jones, S. E., Fermentations in- 247. Nunokawa, Y., Physiological aspects of yeast in
volved in the production of cocoa, coffee and tea, sake fermentation, Crit. Rev. Biotechnol., 2, 193,
Prox. lnd. Microbiol., 19, 41 I , 1984. 1985.
231. Sanchez, J., Guiraud, J. P., and Galzy, P., A 248. Margalith, P. Z., Flavour Microbiology, Charles C
study of the polygalacturonase activity of several yeast Thomas, Springfield, IL, 1982.
strains isolated from cocoa, Appl. Microbiol. Bio- 249. Ferreira, J. D., The growth and fermentation char-
technol., 20, 262, 1984. acteristics of six yeast strains at several temperatures,
232. Sanchez, J . , Daguenet, G., Guiraud, J. P . , Am. J. Enol. Vitic., 10, 1, 1959.
Vincent, J. C., and Galzy, P., A study of the yeast 250. Guymon, J. F., Ingraham, J. L., and Crowell,
flora and the effect of pure culture seeding during the E. A., Influence of aeration upon the formation of
fermentation process of cocoa beans, Lebensm. Wiss. higher alcohols by yeasts, Am. J. Enol. Vitic., 12,
Technol., 18, 69, 1985. 60, 1961.
233. Ardhana, M. and Fleet, G. H., The microbial ecol- 251. Van Zyl, J. A., De Vries, M. J., and Zeeman,
ogy of tape ketan fermentation, Inr. J. Food Micro- A. S., The microbiology of South African winemak-
hiol.. 9, 157, 1989. ing. 111. The effect of different yeasts on the com-
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

234. Adegoke, G. 0. and Babalola, A. K., Character- position of fermented musts, S . Afr. J. Agric. Sci.,
istics of microorganisms of importance in the fer- 6, 165, 1963.
mentation of fufu and ogi - two Nigerian foods, J. 252. Rankine, B. C., Formation of higher alcohols by
Appl. Bacteriol., 65, 449, 19118. wine yeasts and relationship to taste thresholds, J.
235. Ofuya, C. 0. and Nnajiofor, C., Development and Sci. Food Agric., 18, 583, 1967.
evaluation of a starter culture for the industrial pro- 253. Bertrand, A., Utilisation de la chromatographie en
duction of gari, J . Appl. Bacteria/., 66, 37, 1989. phase gazeuse pour le dosage des constituents volatils
236. Puspito, H. J. and Fleet, G. H., Microbiology of du vin, Conn. Vigne Vin, 2, 175, 1968.
sayur asin fermentation, Appl. Microbiol. Eiotech- 254. Sponholz, V. W. R. and Dittrich, H. H., Die Bil-
nol., 2 2 , 442, 1985. dung von SO, - bindenden Ghngs-Nebenproduk-
237. Walker, H. W., Spoilage of food by yeasts, Food ten hoheren Alkoholen und Estern bei einigen Rein-
Technol., 31, 57, 1977. zuchthefestammen und bei einigen fur die
238. Peppler, H. J., Yeast properties adversely affecting Weinbereitung wichtigen “wilden” Hefen, Wein
food fermentation, Food Technol., 3 I , 62, 1977. Wiss., 29, 301, 1974.
239. Miller, M. W., Yeasts in food spoilage: an update, 255. Soufleros, E. and Bertrand, A., R61e de la souche
Food Technol., 33, 76, 1979. de levure dans la production des substances volatiles
240. Rose, A. H., Responses to the chemical environ- au cours de la fermentation du jus de raisin, Conn.
ment, in The Yeasts, Vol. 2, 2nd ed., Rose, A. H. Vigne Vin, 13, 181, 1979.
and Harrison, J. S., Eds., Academic Press, London, 256. Shimazu, Y. and Watanabe, M., Effects of yeast
1987, 5. strains and environmental conditions on formation o f
241. Gancedo, C. and Serrano, R., Energy-yielding me- organic acids in must during fermentation, J. Fer-
tabolism, in The Yeasts, Vol. 3,2nd ed., Rose, A. H. ment. Technol., 59, 27, 1981.
and Harrison, J. S., Ed., Academic Press, London, 257. Shinohara, T., L’importance des substances vola-
1989, 205. tiles due vin. Formation et effets sur la qualiti, Bull.
242. Berry, D. R. and Brown, C., Physiology of yeast O.I.V., 57, 606, 1984.
growth, in Yeast Biotechnology, Berry, D. R., Rus- 258. Cottrell, T. H. E. and McLellan, M. R., The effect
sell, I., and Stewart, G. G., Eds., Allen & Unwin, of fermentation temperature on chemical and sensory
London, 1987, 159. characteristics of wines from seven grape cultivars
243. Castillo, F. J., Lactose metabolism by yeasts, in grown in New York State, Am. J . Enol. Vitic., 37,
Yeast Biotechnology and Biocatalysis, Verachtert, H. 190, 1986.
and de Mot, R., Eds., Marcel Dekker, New York, 259. Cantarelli, C., Influence des temperatures de fer-
1990, 297. mentation et de conservation du vin et des vins spk-
244. Nykiinen, L., Formation and Occurrence of flavour ciaux, Bull. O.I.V., 39, 1191, 1966.
compounds in wine and distilled alcoholic beverages, 260. Usseglio-Tomasset, L., Gli acidi volatili omologhi
Am. J. Enol. Vitic., 37, 84, 1986. dell’acetico nei fermentati con specie diverse di liev-
245. Simpson, R. F., Some important aroma components iti, Att. Accad. Ital. Vite Vino, 19, 165, 1967.
of white wine, Food Technol. Aust., 31, 516, 1979. 261. Goto, S., Yamazaki, M., Yamakawa, Y., and

38
 Yokotsuka, I., Decomposition of malic acid in grape 279. Federici, F., A note on the milk clotting ability in
must by wine and wild yeasts, Hakkokogaku, 56, the yeast genera Cryptococcus and Rhodotorula, J .
133, 1978. Appl. Bacteriol., 52, 293, 1982.
262. Yong, F. M., Lee, K. H., and Wong, H. A., The 280. Nelson, G. and Young, T. W., Yeast extracellular
production of volatile acids from glucose from soy proteolytic enzymes for chill-proofing beer, J . Inst.
yeast (Saccharomyces rouxii NRRCY- 1096),J. Food Brew., 92, 599, 1986.
Technol., 15, 421, 1980. 281. Lagace, L. S. and Bisson, L. F., Survey of yeast
263. Yong, F. M., Lee, K. H., and Wong, H. A., The acid proteases for effectiveness of wine haze reduc-
produetion of ethyl acetate by soy yeast Saccharo- tion, Am. J. Enol. Vitic., 41, 147, 1990.
myces rouxii, NRRLY-1096, J. Food Technol., 16, 282. Bilinski, C. A. and Stewart, G. G., Yeast proteases
177, 1981. and brewing, in Yeast Biotechnology and Biocata-
264. Large, P. J., Degradation of organic nitrogen com- lysis, Verachtert, H. and De Mot, R., Eds., Marcel
pounds by yeasts, Yeast, 2, 1 , 1986. Dekker, New York, 1990, 147.
265. Akita, O., Ida, T., Obata, T., and Hara, S., Mu- 283. Bilinski, C. A., Emery, C. J., Zygora, P. S.,
tants of Saccharomyces cerevisiae producing a large Russell, I., and Stewart, G. G., Application of
quantity of P-phenylethyl alcohol and P-phenylethyl extracellular yeast proteinases in beer stabilization,
acetate, J. Ferment. Bioeng., 69, 125, 1990. Crit. Rev. Biotechnol., 8, 1 1 , 1988.
266. Lee, C. W. and Richard, J., Catabolism of L-phe- 284. Nelson, G. and Young, T. W., Extracellular acid
nylalanine by some microorganisms of cheese origin, and alkali proteases from Candida olea, J. Gen. Mi-
J. Dairy Res., 51, 461, 1984. crobiol., 133, 1461, 1987.
267. Radler, F., Microbial biochemistry, Experientia, 42, 285. Ogrydziak, D. M., Production of alkaline extracel-
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

884, 1986. lular protease by Yarrowia lipolytica, Crit. Rev. Bio-

268. Monk, P. R. and Cowley, P. J., Effect of nicotinic technol., 8, 177, 1988.
acid and sugar concentration of grape juice and tem- 286. Douglas, L. J., Candida proteinases and candidosis,
perature on accumulation of acetic acid during yeast Crit. Rev. Biotechnol., 8, 121, 1988.
fermentation, J. Ferment. Technol., 62, 515, 1984. 287. Rosi, I., Costamagna, L., and Bertuccioli, M.,
269. Viegas, C. A., Rosa, F. M., Sa Correia, I., and Screening for extracellular acid protease(s) produc-
Novais, J. M., Inhibition of yeast growth by octanoic tion by wine yeasts, J. Inst. Brew., 93, 322, 1987.
and decanoic acids produced during ethanolic fer- 288. Sturley, S. L. and Young, T. W., Chill proofing
mentation, Appl. Environ. Microbiol., 55, 21, 1989. by a strain of Saccharomyces cerevisiae secreting
270. Edwards, C. G., Beelman, R. B., Bartley, C. E., proteolytic enzymes, J. Inst. Brew., 94, 133, 1988.
and McConnell, A. C., Production of decanoic acid 289. Stead, D., Microbial lipases: their characteristics,
and other volatile compounds and the growth of yeast role in food spoilage and industrial uses, J. Dairy
and malolactic bacteria during vinification, Am. J. Res., 53, 481, 1986.
Enol. Vitic., 41, 48, 1990. 290. Chopra, A. and Khuller, G. K., Lipid metabolism
271. Corte-Real, M. and Leao, C., Transport of malic of fungi, Crir. Rev. Microbiol., 1 1 , 209, 1986.
acid and other dicarboxylic acids in the yeast Han- 291. Ratledge, C. and Evans, C. T., Lipids and their
senula anomula, Appl. Environ. Microbiol., 56, 1109, metabolism, in The Yeasts, 2nd ed., Vol. 3, Rose,
1990. A. H. and Harrison, J. S., Academic Press, London,
272. Monk, P. R., Formation, utilization, and excretion 1989, 367.
of hydrogen sulphide by wine yeast, Aust. N. Z. Wine 292. Ratledge, C. and Tan, K. H., Oils and fats: pro-
Ind. J . , 1, 10, 1986. duction, degradation and utilization by yeasts, in Yeast
273. Stratford, M. and Rose, A. H., Hydrogen sulphide Biotechnology and Biocatalysis, Verachtert, H. J.
production from sulphite by Saccharomyces cerevis- and De Mot, R., Eds., Marcel Dekker, New York,
iae, J . Gen. Microbiol., 131, 1417, 1985. 1990, 223.
274. Tini, V., Romano, P., Suzzi, G., Arfelli, G., and 293. Castanon-VClez, M., and Leal, V. I., Microorgan-
Zironi, R., Yeast characteristics as factors affecting isms in margarine deterioration, Lebensm. Wiss.
stability of wine colour, Ind. Bev. 17 (February), 12, Technol., 6, 70, 1973.
1988. 294. Bows, J. and Mossell, D. A. A,, A comparison of
275. Rankine, B. C., Hydrogen sulfide production by methods for the determination of lipolytic properties
yeasts, J. Sci. Food Agric., 15, 872, 1964. of yeasts mainly isolated from margarine, moulds and
276. Kalisz, H. M., Microbial proteases, Adv. Biochem. bacteria, Arch. Lebensmittelhyg., 24, 197, 1973.
Eng. Biotechnol., 36, I , 1988. 295. Smith, J. L. and Alford, J. A., Action of micro-
277. Ahearn, D. G . , Meyers, S. P., and Nichols, R. A., organisms on the peroxide and carbonyls of fresh
Extracellular proteinases of yeast and yeast-like fungi, lard, J. Food Sci., 34, 75, 1969.
Appl. Microbiol., 16, 1370, 1968. 296. Tan. K. H. and Gill, C. O., Batch growth of Sac-
278. Carini, S., Carbrini, A., Todesco, R., Vezzoni, A., charomycopsis lipolytica on animal fats, Appl. Mi-
and Saracchi, S., Caseinolytic exo- and endo-cel- crobiol. Biotechnol., 21, 292, 1985.
lular systems of yeasts and their role in ripening of 297. Green. J. H., Paskell, S. L., and Goldmintz, D.,
cheese, Latte, 52, 153, 1975. Lipolytic fermentations of stickwater by Geotrichum

39
 candidurn and Candida lipolytica, Appl. Environ. Mi- 314. Vaughn, R. H., Jakabzyk, T., MacMillan, J. D.,
crobiol., 31, 569, 1976. Higgins, T. E., Dave, B. A., and Crampton, V. M.,
298. Jonsson, U., Rates of hyrolysis of olive oil, soya Some pinks yeasts associated with the softening of
bean oil and linseed oil by Saccharmyocopsis lipol- olives, Appl. Microbiol., 18, 771, 1969.
ytica and Micrococcus caseolyticus, Chem. Mikro- 315. McKay, A. M., Degradation of polygalacturonic acid
biol. Technol. Lebensrn., 4, 139, 1976. by Saccharomyces cerevisiae, Lett. Appl. Microbiol. ~

299. Fitzgerald, C. H. and Deeth, H. C., Factors influ- 11, 41, 1990.
encing lipolysis by skim milk cultures of some psy- 3 16. Petruciolo, M., Monteleone, E., and Federici, F.,
chrotrophic microorganisms, Aust. J. Dairy Tech- Optimization of polygalacturonase production by Au-
nol., 97, 1983. reobasidium pullulans on orange peel waste, Yeast,
300. Woo, A. H. and Lindsay, R. C., Characterization 5(Spec. Iss.), S157, 1989.
of lipase activity in cold stored butter, J . Dairy Sci., 317. Harris, J. E. and Dennis, C., The stability of pec-
67, 1194, 1984. tolytic enzymes in sulphite liquor in relation to break-
301. Shelley, A. W., Deeth, H. C., and MacRae, I. C., down of sulphited strawberries, J. Sci. Food Agric.,
Review of methods of enumeration detection and oso- 30, 704, 1979.
lation of lipolytic microorganisms with special ref- 318. Biely, P., VrSanskB, M., and Krhtky, Z., Xylan-
erence to dairy applications, J. Microbiol. Methods, degrading enzymes of the yeast Cryptococcus albi-
6, 123, 1987. dus, Eur. J. Biochern., 108, 313, 1980.
302. Spencer-Martins, I. and Van Uden, N., Yields of 319. Lee, H., Biely, P., Latta, R. K., Barbosa, M. F. S.,
yeast growth on starch, Eur. J. Appl. Microbiol., 4, and Schneider, H., Utilization of xylan by yeasts
29, 1977. and its conversion to ethanol by Pichia stipitis strains.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

303. McCann, A. K. and Barnett, J. A., The utilization Appl. Environ. Microbiol., 52, 320, 1986.
of starch by yeasts, Yeasts, 2, 109, 1986. 320. Stokes, J. L., Influence of temperature on the growth
304. De Mot, R. and Verachtert, H., Some microbiol- and metabolism of yeasts, in The Yeasts, Vol. 2,
ogical and biochemical aspects of starch bioconver- Physiology and Biochemistry of Yeasts, Rose, A. H.
sion by amylolytic yeasts, Crit. Rev. Biotechnol., 5. and Harrison, J. S., Eds., Academic Press, London,
259, 1987. 1971, 119.
305. Stewart, G. G. and Russell, I., Biochemical and 321. Van Uden, N., Temperature profiles of yeasts, Adv.
genetic control of sugar and carbohydrate metabolism Microbiol. Physiol., 25, 195, 1984.
in yeasts, in Yeast Biotechnology, Berry, D. R., Rus- 322. Watson, K. G., Temperature relations, in The Yeasts.
sell, I., and Stewart, G. G., Eds., Allen & Unwin, Vol. 2, 2nd ed., Yeasts and the Environment, Rose,
London, 1987, 277. A. H. and Harrison, J. S . , Eds., Academic Press,
306. De Mot, R., Conversion of starch by yeasts, in Yeast London, 1987, 41.
Biotechnology and Biocatalysis, Verachtert, H. and 323. Davenport, R. R., Cold-tolerant yeasts and yeast-
De Mot, R., Eds., Marcel Dekker, New York, 1990, like organisms, in Biology and Activities of Yeasts,
163. Skinner, F. A., Passmore, S. M., and Davenport, R .
307. Jeffries, T. W., Fermentation of D-xylose and cel- R., Eds., Academic Press, London, 1980, 215.
lobiose, in Yeast Biotechnology and Biocatalysis, 324. Jermini, M. F. and Schmidt-Lorenz, W., Cardinal
Verachtert, H. and De Mot, R., Eds., Marcel Dekker, temperatures for growth of osmotolerant yeasts in
New York, 1990, 349. broths at different water activity values, J. Food Pro-
308. Dennis, C., Breakdown of cellulose by yeast species, tect., 50, 473, 1987.
J. Gen. Microbiol., 71, 409, 1972. 325. Eubanks, V. L. and Beuchat, L. R., Combined
309. Stevens, B. J. H. and Payne, J., Cellulase and effects of antioxidants and temperature on the sur-
xylanase production by yeasts of the genus Tricho- vival of Saccharomyces cerevisiae. J. Food Protect.,
sporon. J. Gen. Microbiol., 100, 381, 1977. 46, 29, 1983.
310. Zimmermann, M. and Emeis, C. C., Extracellular 326. Curran, D. M. and Montville, T. J., Bicarbonate
polysaccharidases from Trichosporon heigelii, Yeast, inhibition of Saccaromyces cerevisiae and Hansenula
5(spec. 1Ss.1, s131, 1989. wingei growth in apple juice, Int. J. Food Microbiol.,
31 1 . Wirnborne, M. P. and Rickard, P. A., Pectinolytic 8, I , 1989.
activity of Saccharomyces fragilis cultured in con- 327. Van Uden, N., Effects of alcohols on the temperature
trolled environments, Biotechnot. Bioeng., 20, 23 1 , relations of growth and death in yeasts, in Alchohol
1978. Toxicity in Yeasts and Bacteria, Van Uden, N . , Ed.,
312. Call, H. P., Harding, M., and Emeis, C. C., CRC Press, Boca Raton, FL, 1989, 77.
Screening for pectinolytic Candida yeasts: optimi- 328. Bisson, J., Daulny, B., and Bertrand, A., Influ-
zation and characterization of the enzymes, J. Food ence de la temperature de fermentation sur la com-
Biochern., 9, 193, 1985. position d’un vin blanc sec, Conn. Vigne Vin, 14,
3 13. Federici, F., Production, purification and partial 195, 1980.
characterization of an endopolygalacturonase from 329. D’Amore, T. and Stewart, G. G., Ethanol tolerance
Cryprococcus albidus ver albidus, Antonie van Leeu- of yeast, Enzymes Microbiol. Technol., 9,322, 1987.
wenhoek; J . Microbiol. Serol., 51, 139, 1985. 330. Gao, C. and Fleet, G. H., The effects of temperature

40
 and pH on the ethanol tolerance of the wine yeasts, resistance of spoilage yeasts, J. Food Sci., 43, 1074,
Saccharomyces cerevisiae, Candida stellata and 1978.
Kloeckera apiculta, J. Appl. Bacteriol., 65,405, 1988. 346. Corry, J. E. L., Relationships of water activity to
331. Tsang, E. W. T. and Ingledew, W. M., Studies on fungal growth, in Food and Beverage Mycology, 2nd
the heat resistance of wild yeasts and bacteria in beer, ed., Beuchat, L. R., Ed., Van Nostrand Reinhold,
J. Am. SOC. Brew., 40, 1, 1982. New York, 1987, 51.
332. Put, H. M., de Jong, J., Sand, F. E. M. T., and 347. Brown, A. D., Compatible solutes and extreme water
Van Grinsven, A. M., Heat resistance studies on stress in eukaryotic microorganisms, Adv. Microbiol.
yeast spp. causing spoilage in soft drinks, J. Appl. Physiol., 17, 181, 1978.
Bacteriol., 40, 135, 1976. 348. Edgley, M. and Brown, A. D., Yeast water rela-
333. Put, H. M. C. and de Jong, J., The heat resistance tions: physiology changes induced by solute stress in
of ascospores of four Saccharomyces spp. isolated Saccharomyces cerevisiae and Saccharomyces rouxii,
from spoiled heat-processed soft drinks and fruit J. Gen. Microbiol., 129, 3453, 1983.
products, J. Appl. Bacreriol., 52, 235, 1982. 349. Nobre, M. F. and Da Costa, M. S., The accu-
334. Sptittstoesser, D. F., Lienk, L. L., Wilkinson, M., mulation of polyols by the yeast Debaryomyces han-
and Stamer, J. R., Influence of wine composition senii in response to water stress, Can. J. Microbiol.,
on the heat resistance of potential spoilage organisms, 31, 1061, 1985.
Appl. Microbiol., 30, 369, 1975. 350. Adler, L., Blomberg, A., and Nilsson, A., Glyercol
335. Beuchat, L. R., Effects of potassium sorbate and metabolism and osmoregulation in salt tolerant yeast,
sodium benzoate on inactivating yeasts heated in broths Debaryomyces hansenii, J . Bacteriol., 162, 300,
containing sodium chloride and sucrose, J. Food Pro- 1985.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

tect., 44,765, 1981. 351. Van Eck, J. H., Prior, B. A., and Brandt, E. V.,
336. Beuchat, L. R., Synergistic effects of potassium sor- Accumulation of polyhydroxy alcohols by Hansenula
bate and sodium benzoate on thermal inactivation of anomala in response to water stress, J. Gen. Micro-
yeasts, J. Food Sci., 46, 771, 1981. biol., 135, 3505, 1989.
337. Beuchat, L. R., Combined effects of food preserv- 352. Panchal, C. J. and Stewart, G. G., The effect of
atives and organic acids on thermal inactivation of osmotic pressure on the production and excretion of
yeasts in fruit juices, Lebensm. Wiss. Technol., 16, ethanol and glycerol by a brewing yeast strain, J.
51, 1983. Inst. Brew., 86, 207, 1980.
338. Bariller2, J. M., Bidan, P., and Dubois, C., Ther- 353. Spencer, J. F. T. and Spencer, D. M., Production
morksistance des levure et des batteries lactiques is- of polyhydroxy alcohols by osmotolerant yeasts, in
olees du vin, Bull. O.I.V., 627, 327, 1983. Economic Microbiology, Vol. 2, Rose, A. H., Ed.,
339. Beuchat, L. R., Thermal inactivation of yeasts in Academic Press, London, 1978, 393.
fruit juices supplemented with food preservatives and 354. Jermini, M. F. G., Weber, K., and Schmidt-
sucrose, J. Food Sci., 47, 1679, 1982. Lorenz, W., Influence of prolonged culture storage
340. Guerzoni, M. E., Gardini, F., and Duan, J., In- on the osmotolerance of Zygosaccharomyces yeasts,
teractions between inhibition factors on microbial sta- J. Food Protect., 50, 514, 1987.
bility of fruit-based systems, Int. J. Food Microbiol., 355. Sauer, F., Control of yeasts and moulds with pre-
10, 1 , 1990. servatives, Food Technol., 31, 66, 1977.
341. Corry, J. E. L., The effect of sugars and polyols 356. Pitt, J. I. and Richardson, K. C., Spoilage by
on the heat resistance and morphology of osmophilic preservative-resistant yeasts, CSIRO Food Res. Q . ,
yeasts, J. Appl. Bacteriol., 40, 269, 1976. 33, 80, 1973.
342. Berger, M. A., Richard, N., and Cheffel, J. C., 357. Warth, A. D., Preservative resistance of Zygosac-
Influence de I’activitk de I’eau sur la thermoresistance chromyces bailii and other yeasts, CSIRO Food Res.
d’une levure osmophile: Saccharomyces rouxii, dans Q . , 46, 1 , 1986.
un aliment a humiditt intermediare, Lebensm. Wiss. 358. Pitt, J. I., Resistance of some food spoilage yeasts
Technol., 15, 83, 1982. to preservatives, Food Technol. Aust., 26,238, 1974.
343. Jermini, M. F. G. and Schmidt-Lorenz, W., Heat 359. Jermini, M. F. G. and Schmidt-Lorenz, W., Ac-
resistance of vegetative cells and asci of two Zygo- tivity of Na-benzoate and ethyl-paraben against os-
saccharmoyces yeasts in broths of different water motolerant yeasts of different water activity values,
activity values, J. Food Protect., 50, 835, 1987. J . Food Protect., 50, 920, 1987.
344. Su, W., Beuchat, L. R., and Worthington, R. E., 360. Cole, M. B. and Keenan, M. H. J., Synergistic
Independent development of heat resistance and as- effects of weak-acid preservatives and pH on the
copores in Hansenula anomala, Can. J . Microbiol., growth of Zygosaccharomyces bailii, Yeast, 2, 93,
31, 45, 1984. 1986.
345. Juven, B. J., Kanner, J., and Weisslowicz, H., 361. Bills, S., Restaino, L., and Lenovich, L. M., Growth
Influence of orange juice composition on the thermal response of an osmotolerant sorbate resistant yeast,

41
 Saccharomyces rouxii at different sucrose and sorbate phur dioxide resistance in Saccharomyces cerevisiae
levels, J. Food Protect., 45, 1 120, 1982. and Sacchclromycodes ludwigii, J. Gen. Microbiol.,
362. Liewen, M. B. and Marth, E. H., Growth and 133, 2173, 1987.
inhibition of microorganisms in the presence of sorbic 379. Debevre, J. M., The use of buffered acidulant sys-
acid: a review, J. Food Prorect., 48, 364, 1985. tems to improve the microbiological stability of acid
363. Splittstoesser, D. F., Microorganisms in the spoilage foods, Food Microbiol., 4, 105, 1987.
of fermented fruit juices, J . Food Protect., 45, 874, 380. Moon, N. J., Inhibition of the growth of acid tolerant
1982. yeasts by acetate, lactate and propionate and their
364. Restaino, L., Lenovich, L. M., and Bills, S., Effect synergistic mixtures, J. Appl. Bacteriol., 5 5 , 453,
of acids and sorbate combinations on the growth of 1983.
four osmophilic yeasts, J. Food Protect., 45, 1138, 381. Siuhko, M. L. and Makinen, V., Tolerance of ace-
1982. tate, propionate and sorbate by Saccharomyces cere-
365. Warth, A. D., Effect of benzoic acid on growth visiae and Toru10psi.s holmi, Food Microbiol., 1, 105,
yields of yeasts differing in their resistance to pre- 1984.
servatives, Appl. Environ. Microbiol., 54,2091, 1988. 382. Jones, R. P. and Greenfield, P. F., Effect of carbon
366. Romano, P. and Suzzi, G., Sensitivity of Saccha- dioxide on yeast growth and fermentation, Enzymes
romyres cerevisiae vegetative cells and spores to an- Microbial. Technol., 4, 210, 1982.
tiniicrobial compounds, J. Appl. Bucteriol., 59, 299, 383. Dixon, N. M. and Kell, D. B., The inhibition by
1985. CO, of the growth and metabolism of microorgan-
367. Eklund, T., Organic acids and esters, in Mechanisms isms, J. Appl. Bacteriol., 67, 109, 1989.
of Action of Food Preservation Procedures, Could, 384. Slaughter, J. C., The effects of carbon dioxide on
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

G. W., Ed., Elsevier, London, 1989, 161. yeasts, in Biotechnology Applications in Beverage
368. Warth, A. D., Resistance of yeast species to benzoic Production, Cantarelli, C . and Lanzarini, G., Eds.,
and sorbic acids and to sulfur dioxide, J. Food Pro- Elsevier, London, 1989, 49.
tect., 48, 5 6 4 , 1985. 385. Haas, G. J., Prescott, H. E., Dudley, E., Dik, R.,
369. Warth, A. D., Relationships between the resistance Hintlian, C., and Keane, L., Inactivation of mi-
of yeasts to acetic, propanoic and benzoic acids to croorganisms by carbon dioxide under pressure, J.
methyl paraben and pH, Int. J . Food Microbiol., 8, Food Safety, 9, 253, 1989.
343, 1989. 386. Hoover, D. G., Metrick, C., Papineau, A. M.,
370. Warth, A. D., Relationships among cell size, mem- Farkas, D. F., and Knorr, D., Biological effects
brane permeability, and preservative resistance in yeast of high hydrostatic pressure on food microorganisms,
species, Appl. Environ. Microbiol., 5 5 , 2995, 1989. Food Technol., March, 99, 1989.
371. Warth, A. D., Transport of benzoic and propanoic 387. Cahill, J. T., Carroad, P. A., and Kunkee, R. E.,
acids by Zygosaccharomyces bailii, J. Gen. Micro- Cultivation of wine yeast under carbon dioxide pres-
biol., 135, 1383, 1989. sure for use in continuous sparkling wine production,
372. Cole, M. B. and Keenan, M. H. J., Effects of weak Am. J. Enol. Vitic., 31, 46, 1980.
acids and external pH on the intracellular pH of Zyg- 388. Ison, R. W. and Gutteridge, C. S., Determination
osaccharomyces bailii, and its implications in weak- of the carbonation tolerance of yeasts, Lett. Appl.
acid resistance, Yeast, 3, 23, 1987. Microbiol.. 5, 1 1 , 1987.
373. King, A. D., Ponting, J. D., Sanshuck, D. W., 389. Despasquale, D. A., El-Nabarawy, A., Rosen,
Jackson, R., and Mihara, K., Factors affecting death J. D., and Montville, T. J., Ammonium bicarbon-
of yeast by sulfur dioxide, J. Food Protect., 44, 92, ate inhibition of mycotoxigenic fungi and spoilage
1981. yeasts, J. Food Protect., 53, 324, 1990.
374. Beech, F. W. and Thomas, S., Action antimicro- 390. Fleet, G. H., Cell walls, in The Yeasts, Vol. 4, 2nd
bienne de I’anhydride sulfureux, Bull. O.I.V., 58, ed., Rose, A . H. andHarrison, J. S . , Eds., Academic
564, 1985. Press, London, 1990, 200.
375. Rose, A. H. and Pilkington, B. J., Sulphite, in 391. Farrer, K. H., The autolysis of yeasts, Food Sci.
Mechanisms of Action of Food Preservation Proce- Abstr., 28, 1, 1956.
dures, Could, G. W., Ed., Elsevier, London, 1989, 392. Arnold, W. N., Autolysis, in Yeast Cell Envelopes:
201. Biochemistry, Biophysics and Ultrastructure, Vol. 2 ,
376. Pilkington, P. J. and Rose, A. H., Reactions of Arnold, W. N., Ed., CRC Press, Boca Raton, FL,
Saccharomyces cerevisiae and Zygosaccharomyces 1981, 129.
bailii to sulphite resistance, J. Gen. Microbiol., 134, 393. Leroy, M. J., Charpentier, M., Duteurtre, B.,
2823, 1988. Feuillat, M., and Charpentier, C., Yeast autolysis
377. Heard, G. M. and Fleet, G. H., The effect of sul- during champagne aging, Am. J. Enol. Vitic., 41,
phur dioxide on yeast growth during natural and in- 21, 1990.
oculated wine fermentations, Aust. N . Z . Wine Ind. 394. Masschelein, C. A., The biochemistry of matura-
J.. 3, 57, 1988. tion, J. Inst. Brew., 92, 213, 1986.
378. Stratford, M., Morgan, P., and Rose, A. H., Sul- 395. Peppler, H. J., Yeast extracts, in Fermented Foods,

42
 Economic Microbiology, Vol. 7, Rose, A. H., Ed., foods, in Developments in Food Microbiology, Vol.
Academic Press, London, 1982, 293. 1, Davies, R., Ed., Applied Science, London, 1982,
396. Davenport, R. R., An outline guide to media and 183.
methods for studying yeasts and yeast-like organisms, 411. Jarvis, B., and Easter, M. C., Rapid methods in
in Biology and Activities of Yeasts, Skinner, F. A,, the assessment of microbiological quality: experi-
Passmore, S. M., and Davenport, R. R., Eds., AC- ences and needs, J. Appl. Bacteriol. Symp. Suppl.,
ademic Press, London, 1980, 261. 63, 1155, 1987.
397. Mossel, D. A. A., Dijkmann, K. E., and 412. Firstenberg-Eden, R. and Zindulus, J., Rapid au-
Koopmans, M., Experience with methods for the tomated methods, in Food Microbiology, Vol. 2, New
enumeration and identification of yeasts occumng in and Emerging Technologies, Montville, T. J . , Ed.,
foods, in Biology and Activities of Yeasts, Skinner, CRC Press, Boca Raton, FL, 1987, 15.
F. A., Passmore, S. M . , and Davenport, R. R., Eds., 413. Zindulus, J., A medium for the impedimetric de-
Academic Press, London, 1980, 279. tection of yeasts in foods, Food Microbiol., 1, 159,
398. Koburger, J. A. and Marth, E. H., Yeasts and 1984.
moulds, in Compendium of Methods for the Micro- 414. Schaertel, B. J., Tsang, N., and Firstenberg-
biological Examination of Foods, 2nd ed., Speck, Eden, R., Impedimetric detection of yeast and mould,
M. L., Ed., American Public Health Association, Food Microbiol., 4, 155, 1987.
Washington, D.C., 1984, 197. 415. Connolly, P., Lewis, S. J., and Corry, J. E. L.,
399. Pitt, J. I. and Hocking, A. D., Fungi and Food A medium for the detection of yeasts using a con-
Spoilage, Academic Press, Sydney, 1985, chap. 10. ductimetric method, Int. J. Food Microbiol., 7, 31,
400. Jarvis, B. and Williams, A. P., Methods for de- 1988.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

tecting fungi in foods and beverages, in Food and 416. Watson-Craik, I. A., Aidoo, K. E., and Anderson,
Beverage Mycology, Beuchat, L. R., Ed., Van Nos- J. G., Development and evaluation of a medium for
trand Reinhold, New York, 1987, 599. the monitoring of food-borne moulds by capacitance
401. King, A. P., Pitt, J. I., Beuchat, L. R., and Corry, changes, Food Microbiol., 7, 129, 1990.
J. E. L., Methods for the Mycological Examination 417. Weihe, J. L., Serbt, S. L., and Hatcher, W. S.,
of Food, Plenum Press, New York, 1986. Estimation of microbial populations in frozen con-
402. Restaino, L., Bills, S., and Lenovich, L. M., Growth centrated orange juice using automated impedance
response of an osmotolerant sorbate-resistant Sac- measurements, J. Food Sci., 49, 243, 1984.
charomyces rouxii strain: evaluation of plating media, 418. Fleischer, M., Shapton, N., and Cooper, P. T.,
J . Food Protect., 48, 207, 1985. Estimation of yeast numbers in fruit mix for yogurt,
403. Banks, J. G. and Board, R. G., Some factors in- J. SOC. Dairy Technol., 37, 63, 1984.
fluencing the recovery of yeasts and moulds from 419. Henschke, P. A. and Thomas, S., Detection of
chilled foods, Inr. J. Food Microbiol., 4, 197, 1987. wine-spoiling yeasts by electronic methods, J. Appl.
404. De Jong, J. and Put, H. M. C., Enumeration of Bacteriol., 64, 123, 1988.
yeasts in the presence of mould, in Biology and Ac- 420.. Kyriakides, A. L. and Thurston, P. A., Conduct-
tivity of Yeasts, Skinner, F. A., Passmore, S. M., ance techniques for the detection of contaminants in
and Davenport, R. R., Eds., Academic Press, Lon- beer, in Rapid Microbiological Methods for Foods,
don, 1980, 289. Beverages and Pharmaceuticals, Stannard, C. J . , Pe-
405. Heard, G. M. and Fleet, G. H., Evaluation of se- titt, S. B., and Skinner, F. A., Eds., Blackwell Sci-
lective media for enumeration of yeasts during wine entific, Oxford, 1989, 101.
fermentation, J. Appl. Bacteriol., 60, 477, 1986. 421. Hysert, D. W., Kovecses, F., and Morrison, N. M.,
406. Kish, S., Sharf, R., and Margalith, P., A note on A firefly bioluminescence ATP assay method for rapid
a selective medium for wine yeasts, J. Appl. Bac- detection and enumeration of brewery microorgan-
teriol., 55, 177, 1983. isms, J. Am. SOC. Brew. Chern., 34, 145, 1976.
407. Stevenson, K. E. and Graumlich, T. R., Injury and 422. Hope, C. F. A. and Tubb, R. S., Approaches to
recovery of yeasts and molds, Adv. Appl. Microbiol., rapid microbial monitoring in brewing, J. Inst. Brew.,
23, 203, 1978. 91, 12, 1985.
408. Beuchat, L. R., Injury and repair of yeasts and 423. Miller, R. and Galston, G., Rapid methods for the
moulds, in The Revival of InjuredMicrobes, Andrew, detection of yeast and Lactobacillus by ATP biolu-
M. H. E. and Russell, A. D., Eds., Academic Press, minescence, J . Inst. Brew., 95, 317, 1989.
London, 1984, 293. 424. Avis, J. W. and Smith, P., The use of ATP biol-
409. Golden, P. A. and Beuchat, L. R., Colony for- uminescence for the analysis of beer in polyethylene
mation by sublethally heat-injured Zygosacchro- terephthalate (PET) bottles and associated plant, in
myces rouxii as affected by solutes in the recovery Rapid Microbiological Methods for Food, Beverages
medium and the procedure for sterilizing medium, and Pharmaceuticals, Stannard, C . J., Petitt, S. B.,
Appl. Environ. Microbiol., 56, 2319, 1990. and Skinner, F. A,, Eds., Blackwell Scientific, Ox-
410. Wood, J. M. and Gibbs, P. A., New developments ford, 1989, 1.
in the rapid estimation of microbial populations in 425. Lonvand-Funel, A. and Joyeux, A., Application de

43
 bioluminescence pour le denombrement des micro- 442. Heard, G. M. and Fleet, G. H., A convenient mi-
organisms vivantes dans les vins, Conn. Vigne Vin, crotitre tray procedure for yeast identification, J. AppI.
16, 241, 1982. Bacteriol.. 68, 447, 1990.
426. La ROCCO,
K. A., Galligan, K. A., Little, K. J., 443. Schmidt, J. L., Evaluation d’une method rapide
and Spurgash, A,, A rapid, bioluminescent ATP d’assimilation des sucres (APT50 CH) en vue de l’i-
method for determining yeast contamination in a car- dentification des levures, Ann. Technol. Agric., 29,
bonated beverage, Food Technol., 39, 49, 1985. 47, 1980.
427. Patel, P. D. and Williams, A. P., A note on esti- 444. Ison, R. W., A revised method for the application
mation of food spoilage yeasts by measurement of of AP150 CH carbohydrate kits to yeasts, Left. Appl.
adenosine triphosphate (ATP) after growth at various Microbiol., 4, 9, 1987.
temperatures, J. Appl. Bacteriol., 59, 133, 1985. 445. Degre, Thomas, D. Y., Ash, J., Mailhiot, K.,
428. Koch, H. A., Bandler, R., and Gibson, R. R., Morin, A,, and Dubord, C., Wine yeasts strain
Fluorescence microscopy procedure for quantitation identification, Am. J. Enol. Vitic., 40, 309, 1989.
of yeasts in beverages, Appl. Environ. Microbiol., 446. Blondin, B. and Vezinhet, F., Identification de
52, 599, 1986. souches de levures oenologique par leurs caryotypes
429. Hutcheson, T. C., McKay, T., Farr, L., and obtenus en electrophorkse en champ pulsC, Rev. Fr.
Seddon, B., Evaluation of the stain Viablue for the Oenol., 28, 7, 1988.
rapid estimation of viable yeast cells, Left. Appl. 447. Petering, J., Langridge, P., and Henschke, P.,
Microbiol., 6, 85, 1988. Fingerprinting wine yeasts, Aust. N.Z. Wine Ind. J . ,
430. Betts, R. P., Bankes, P., and Banks, J. G., Rapid 3, 48, 1988.
Downloaded By: [B-on Consortium - 2007] At: 14:32 4 February 2009

enumeration of viable microorganisms by staining 448. Panchal, C. J., Bast, L., Dowhanick, T., and
and direct microscopy, Lett. Appl. Microbiol., 9, Stewart, G. G., A rapid simple and reliable method
199, 1989. of differentiating brewing yeast strains based on DNA
431. Rodrigues, U. M. and Kroll, R. G., Use of the restriction patterns, 1.Inst. Brew.. 93, 325, 1987.
direct epifluorescent filter technique for the enumer- 449. Van Vuuren, H. J. J. and van der Meer, L., Fin-
ation of yeasts, J . Appl. Bacteriol., 61, 139, 1986. gerprinting of yeasts by protein electrophoresis, Am.
432. Pettipher, G. L., Detection of low numbers of os- J. Enrol. Vitic., 38, 49, 1987.
mophilic yeasts in creme fondant within 25h using a 450. Tredoux, H. G., Kock, J. L. F., Lategan, P. M.,
pre-incubated DEFT count, Lett. Appl. Microbiol., and Muller, H. B., A rapid identification technique
4. 95, 1987. to differentiate between Succharomyces ceruisiae
433. Kreger-van Rij, N. J. W., Classification of yeasts, strains and other yeast species in the wine industry,
in The Yeasts, Vol. 1, Biology of Yeasts, Rose, A. Am. J. Enol. Vific.738, 161, 1987.
H. and Harrison, J. S., Eds., Academic Press, Lon- 451. Oosthuizen, A,, Koch, J. L. F., Viljoen, B. C.,
don, 1987, 5. Muller, H. B., and Lategan, P. M., The value of
434. Kurtzman, C. P., Classification and general prop- long-chain fatty acid composition in the identification
erties of yeasts, in Yeast Biotechnology and Bioca- of some brewery yeasts, J. Inst. Brew., 93, 174,
tulysis, Verachtert, H. and DeMot, R . , Eds., Marcel 1987.
Dekker, New York, 1990, I . 452. Malfeito-Ferreira, M., St. Aubyn, A . , and
435. Kreger-van Rij, N. J. W., The Yeasts - A Tax- Laureriro, V., Long-chain fatty acid composition as
onomic Study, Elsevier, Amsterdam, 1984. a tool for differentiating spoilage wine yeasts, My-
436. Barnett, J. A., Payne, R. W., and Yarrow, D., cotuxon, 36, 35, 1989.
Yeasts: Characteristics and Identifcution. 2nd ed., 453. Kuniyuki, A. H., ROUS,C., and Sanderson, J. L.,
Cambridge University Press, Cambridge, 1990. Enzyme-linked immunosorbent assay (ELISA), de-
437. Lin, C. C. S. and Fung, D. Y. C., Conventional tection of Brettanomyces contaminants in wine pro-
and rapid methods for yeast identification, Crir. Rev. duction, Am. J. Enol. Vitic., 3 5 , 143, 1984.
Microbiol., 14, 273, 1987.
438. Deak, T. and Beuchat, L. R., Identification of food-
borne yeasts, J . Food Protect., 50, 243, 1987.
439. Rohm, H. and Lechner, F., Evaluation and relia-
bility of a simplified method for identification of food-
borne yeasts, Appl. Environ. Microbiol., 56, 1290,
1990.
440. Rodriguez, S. B., A system for identifying spoilage
yeast in packaged wine, Am. J . Eno[. Vitic., 38,273,
1987.
441. Deak, T. and Beuchat, L. R., Evaluation of sim-
plified and commercial systems for identification of
foodborne yeasts, Int. J. Food Microbiol., 7, 135,
1988.

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