ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

UNIT 1: FATS AND OILS

● Fats and oils are triglyceride

compounds of fatty acids and
glycerol
● Belong to a group of organic
compounds: Lipids
● The first dietary fat that was used
by humans probably came from
animal carcasses.
● The domestication of animals
provided another major source of
fat—butter. HEAT TRANSFER
● The seed type determined what
kind of vegetable oil was ● A major function of fats is their
produced—safflower, sunflower, ability to act as a medium for heat
sesame, cottonseed, olive, corn, and transfer
others ● The amount of fat used can range
● A few fruits high in fat such as from the minimal quantities used in
coconut and avocado were also sautéing, to the moderate levels
used to generate oils. used in pan-frying, to enough to
● Food manufacturers added fats to completely submerge a food, as in
their food products to ease deep-frying.
production and handling and
improve storage stability
SHORTENING POWER
● Fats are used not only in the
preparation and formulation of many
foods but are also added directly to ● The shortening power of certain
finished foods fats makes them essential in the
preparation of pastries, piecrusts,
biscuits, and cakes.
FUNCTION OF FATS IN FOOD ● The more highly saturated fats,
which are solid at room
● The unique chemical configuration temperature, tend to be more
of the fat molecule (specifically, the useful shortenings in baked goods.
length and saturation of the three ● Shortening power depends on the
fatty acids on the glycerol consistency of the fat and the
molecule of a triglyceride method of its incorporation into the
● It contributes to the functions of fat in dough.
heat transfer, shortening ● Solid shortenings are necessary to
(tenderizing) power, and make flaky pastry, whereas oils will
emulsions, as well as influences the produce a tender pastry that tends
fat’s melting point, plasticity, to be crumbly rather than flaky
solubility, flavor, texture, ● A fine grain is created from certain
appearance, satiety, and nutrient cake and cookie batters with the use
content. of shortenings that gently encase the
numerous air bubbles, serving as a
starting point for the air to expand
and increase overall volume
● Baked goods become more tender,
up to a point, as fat concentration
increases.

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

tension to increase its wetting and

EMULSIONS
blending ability
● An emulsifying agent can act as a
● All foods contain some amount of bridge between oil and water
liquid, and if fats or oils are present, because it contains two distinct
then the combination results in types of molecular groups, one
some type of emulsion hydrophilic (“water loving”) and the
● Two-Types of Lipid Emulsion: other hydrophobic (“water fearing”)
1. Oil-in-water - oil droplets ● Emulsifiers work not only with
are dispersed throughout the liquids but also with gaseous
water. phases.
2. Water-in-oil - in which water ●
droplets are dispersed
throughout the oil.
● Most food emulsions are of the
first type—oil-in-water
● Examples of such natural
emulsions include milk, cream, and
egg yolks
● Examples of prepared foods that
are emulsions (oil-in-water) include
mayonnaise, salad dressings, ● Emulsifier is added to cake batter
cheese sauces, gravies, puddings, disperses the air bubbles, resulting
and cream soups in a cake with a finer crumb.
● The less common water-in-oil ● Monoglycerides and diglycerides
emulsion, in which the smaller are the most frequently used
amount of water is dispersed in the emulsifiers in the food industry
fat, is found in foods such as butter ● They are added to foods to
and margarine. increase or improve emulsion
● Emulsions have three parts: stability, dough strength, volume,
1. The dispersed or discontinuous texture, and tolerance of ingredients
phase, which is usually oil to processing
2. The dispersion medium or ● Other emulsifiers include
continuous phase, which is most phospholipids (lipoproteins from
likely water based egg yolks)
3. An emulsifier, a compound that ● Emulsions differ in their degree of
helps keep one phase dispersed in stability:
the other 1. Temporary
● The two phases of emulsions are 2. Semipermanent
kept apart by surface tension, and 3. Permanent
the boundary between them is ● Other emulsifiers include
called the interface phospholipids (lipoproteins from
● The emulsifier migrates to this egg yolks)
interface and acts as a surfactant, ● Stability is defined by an emulsion’s
lowering the surface tension capacity to resist separation when
between the dispersed and subjected to gravity, agitation, long
continuous phases so that the two storage times, extreme
phases mix more readily temperatures, surface drying, or
● Emulsion is a liquid dispersed in added salt.
another liquid with which it is ● Temporary Emulsions - are the
usually immiscible (incapable of least viscous and stable; they
being mixed) separate on standing when left
● Surfactant is a surface-active agent alone.
that reduces a liquid’s surface

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● Semipermanent Emulsions - The ● Hydrogenation makes the fat more

tendency of the emulsion to spreadable and increases its shelf
separate is decreased by adding life
stabilizers, which create a viscosity ● Length of the Fatty Acids
similar to that of soft yogurt. - The length of the fatty acids
● Permanent Emulsions - are very can alter these general rules,
viscous and stable, to the point as even saturated fats with
that they do not separate. (e.g. shorter carbon chains can
Mayonnaise) have lower melting points
● The added egg yolk in mayonnaise than fatty acids with longer
contains lipoproteins with lecithin ones
and protein components. These ● Butyric acid and stearic acid are
lipoproteins migrate to the interface saturated fatty acids found in butter
and form a strong, stable interfacial ● Coconut oil is a saturated oil
film that prevents coalescence. containing short fatty acids, which
● The high oil content of mayonnaise causes it to remain solid at room
contributes about 100 kcalories and temperature
11 grams of fat in every ● In general, increasing the chain
tablespoon. length of the fatty acids in a fat
increases its melting point.
● Cis-Trans Configuration
MELTING POINT
- A fatty acid with a trans
configuration has a higher
● Each food fat has a unique melting melting point than an
temperature range that depends on identical fatty acid with a cis
the mixture of fatty acids contained form at the double bond.
in its triglycerides - The “bends” created by cis
● A fat’s melting point is determined double bonds reduce
by the following four interactions, which
characteristics of its predominant decreases the fat’s melting
fatty acids: point.
1. Degree of saturation ● Crystalline Structure
2. Length - The crystalline structure is
3. Cis–trans configuration the arrangement of the
4. Crystalline structure fatty acids on the
● Degree of Saturation triglyceride molecule
- Most plant oils contain more - The larger the fat’s crystals,
polyunsaturated fatty acids the higher the melting point
than saturated fatty acids, will be
which causes them to be ● Polymorphism - ability to exist in
liquid at room temperature. more than one crystalline form.
- Plant oils may be subjected
to hydrogenation, a
commercial process that PLASTICITY
adds hydrogen to the
double bonds of the ● Plasticity describes the ability of a
unsaturated fatty acids. solid fat to hold its shape but still be
● The number of double bonds molded or shaped under light
decreases and saturation pressure.
increases ● Plasticity also determines a fat’s
● Hydrogenated fats are normally spreadability
solid, instead of liquid, at room ● The more unsaturated a fat is, and
temperature. the warmer its temperature, the
more plastic it will be.

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● Chilled butter has very little ● The most abundant sources of fats
plasticity as compared with and oils in the diet are those of
hydrogenated vegetable oil animal origin such as meats, poultry,
(shortening). However, hard fats and dairy products.
such as butter become soft and ● Plants also contribute to dietary fat,
more spreadable when warmed. and the richest sources include nuts,
seeds, avocados, olives, and
coconut
SOLUBILITY

● Fats are generally insoluble in BUTTER

water which is why oil floats above
the vinegar in a salad dressing ● Undisturbed, unhomogenized milk
● Fats are actually defined as fats will separate into its watery and
because they do not dissolve in fatty portions. The cream that
water, but they will dissolve floats to the top is used to make
(become soluble) in organic butter.
compounds such as benzene, ● Butter is made from the cream of
chloroform, and ether. milk
● 10 cups (2½ quarts) of milk are
used to generate one stick (¼
FLAVOR
pound) of butter.
● The U.S. Department of
● The flavor developed in certain Agriculture (USDA) defines butter
foods by fats is very difficult to as 80% milk fat, no more than 16%
duplicate. water, and 4% milk solids.
● Fats not only contribute their own ● In commercial dairies, the process of
flavor to foods but also absorb making butter begins with a cream
fatsoluble flavor compounds from that is concentrated up to 80% fat
other foods. and then further concentrated to
● The soft yellow hue of butter was 98%
found to be so important to ● In India, ghee (clarified butter) is
consumers that attempts were made created by heating and
to duplicate it in margarine concentrating the butter or cream to
over 99% milk fat and less than
SATIETY 0.2% moisture
● This lower-lactose, nutty-tasting
butter has a shelf life of 6 to 8
● Fats induce a sense of fullness, or
months even at ambient or tropical
satiety
temperatures
● Foods and beverages containing
● Waxed paper is usually used to
fat help to delay the onset of
prevent absorption of odors from
hunger pangs by two methods:
other foods.
1. Fats take longer to digest
than carbohydrates and
proteins MARGARINE
2. Fats delay the emptying of
the stomach contents, which ● In 1869, a French pharmacist and
makes a person feel full chemist, Hippolyte Mege Mouries,
longer won the contest by developing
oleomargarine.
● Standard stick margarine must
TYPES OF FATS contain at least 80% fat, about 16%
water, and 4% milk solids, which is

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

very similar to butter’s general ● Diet or reduced-kcalorie

composition margarine - which has a higher
● Margarines usually contain the water content
following: ● Imitation margarine - “vegetable
1. Cultured Skim Milk oil spread”; generally average half
2. Emulsifiers or Surfactants the fat of regular margarines.
such as lecithin
3. Monoglycerides and
SHORTENINGS
diglycerides
4. Preservatives such as
sodium benzoate, potassium ● Shortenings are plant oils that have
sorbate, calcium disodium been hydrogenated to make them
ethylenediaminetetraacetic more solid and pliable
acid (EDTA), isopropyl ● Soybean oil is the major source of
citrate, and citric acid hydrogenated shortening and serves
5. Vitamins A and D as a common frying oil.
6. Flavorings, usually diacetyl ● Many shortenings are also
7. Food colorings, usually superglycerinated, making them
annatto and/ or carotene ideal for baking applications
● Diacetyl is added to margarine for needing solid fat, especially for flaky
flavoring because it is largely pastries and cakes containing more
responsible, in addition to sugar than flour
short-chain fatty acids, for butter’s ● Superglycerinated - describes a
characteristic flavor shortening that has had
monoglycerides and diglycerides
added for increased plasticity
TYPES OF BUTTER

OILS

● Vegetable oils are derived from a

variety of seeds, fruits, and nuts;
comes from soybeans, rapeseed
(canola oil), sunflower seed, corn,
● he less common water-in-oil cottonseed, and safflower seeds.
emulsion, in which the smaller ● Fruit oil sources include the
amount of water is dispersed in the avocado, coconut, palm kernel,
fat, is found in foods such as butter palm, and olive
and margarine. ● Oil production - Oils are obtained
from plant sources through the
process of extraction and are often
refined further thereafter.
● Extraction - The first step in
producing any oil is to extract it from
its original food source—seeds, fruit,
or nuts.
● Oils are removed from their plant
sources by one of the following
three extraction methods:
1. Cold-pressing -
TYPES OF MARGARINE Mechanically pressing the
seeds. Cold-pressed oils are
● Whipped margarine - light blends sometimes sold as
of margarine and butter containing “specialty” oils and are
about 60% fat usually not refined

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

2. Expeller-pressing - ● Cottonseed oil, however, is the

Squeezing the seeds at very leading choice in food-service
high pressures, which may operations for frying potato chips
generate some heat. These and for producing baked goods
oils still retain most of their and snacks.
flavor, color, aroma, and ● Canola, a bland-flavored oil, so
nutrients. named because it was developed in
3. Chemical solvents - Canada; “canola” is a contraction of
Chemically removing the oil “Canadian oil”, low acid.
from the seeds with solvents - derived from rapeseed,
(27). The majority of which has a high
commercial vegetable oils monounsaturated fatty
sold in bottles have been acid content. Rapeseeds
extracted using chemical originally contained high
solvents. They are not levels of erucic acid and
required to be labeled as glucosinolates, which, in
solvent extracted large amounts, were found to
● Refining - produces a neutral, low cause cancer
aroma, bland-flavored oil. ● Strong-flavored oils such as
peanut oil or olive oil vary widely in
quality and character. Because their
flavors are distinctive, these oils
must be used carefully in foods.
● Peanut and sesame seed oils are
more costly than many others, but
their unique flavors make them the
oils most commonly used in
Chinese stir-fry dishes.
● Refined peanut oil is less
expensive and is very heat stable,
making it ideal for high-heat
sautéing and frying.
● Peanut oil’s flavor is preferred by
- Refining, which results in oil that is some snack food manufacturers for
99.5% triglycerides, consists of five their products
steps: degumming, neutralizing, ● Olive oil, which is considered a
washing and drying, bleaching, and specialty oil, is more expensive
deodorizing. than most other vegetable oils.
- Once refined, these oils can be used Despite its higher price, olive oil
as: appeals to health-conscious
1. Medium-heat cooking oils consumers because of its high
(225 to 350°F [107 to 177°C] monounsaturated fatty acid
2. High-heat cooking oils (350 content (77%)
to 450°F [177 to 232°C]), - A qualified health claim for
3. Deep-frying oils - olive oil regarding reducing
(≥450°F/≥232°C). the risk for coronary heart
disease has been approved
by the FDA
TYPES OF OILS
- 2 tablespoons (23 grams)
of olive oil daily may reduce
● Frying oils are mild flavored, bland, the risk of coronary heart
and stable to heat. disease due to the
● Oils ideal for frying include monounsaturated fat in
soybean, corn, and safflower. olive oil.”

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● When it comes to quality, the FDA ● Olive oil and canola oil are valued
has no grades for olive oils, but for their high monounsaturated
following Italian law, olive oils are fatty acid content.
classified according to acidity: the ● Borage oil for its γ-linolenic acid
lower the acid content, the better content
the grade ● Sunflower oil for its high vitamin E
● The term “virgin” means that the oil level
was extracted by mechanical ● Fish oil for its high content of
means only, and not with chemicals omega-3 fatty acids
● Milder olive oils are preferred for
sautéing.
WINTERIZED OILS
● Unrefined olive oils are also
popular in Italian dishes and salad
dressings because of their full flavor ● Some vegetable oils do not remain
● Tropical oils - Food products using completely liquid when stored in
tropical oils such as coconut, palm, the refrigerator. The cooler
and palm kernel oils have longer temperatures may result in
shelf lives. cloudiness from the crystallization
● Foods commonly made with of certain fatty acids that have a
tropical oils include cereals, candy, higher melting point than their
baked items, chocolate coatings for neighboring fatty acids. This
ice cream bars, pressurized whipped cloudiness may be eliminated by
toppings, and dog and cat food winterizing the oil.
● Because saturated fats contain no ● Winterizing is a commercial
double bonds, they break down process for vegetable oils that
less easily than unsaturated fats removes the high-melting point
- Therefore, they do not triglycerides that would otherwise
become rancid as quickly crystallize during low-temperature
when subjected to oxygen, (refrigerator) storage and make the
heat, and light. oil appear cloudy
● Unwinterized vegetable oils that
have crystallized in the refrigerator
are perfectly edible and will revert
to their clear character if allowed to
come to room temperature

HYDROGENATED OILS

OILS AS FUNCTIONAL FOODS ● Hydrogenation makes fats and oils

more solid, allows them to be
● Some oils are marketed as heated to higher temperatures
functional foods because of their without smoking, and increases
favorable fatty acid profile or other their shelf life or that of the foods
purported benefits coated with them
● Flaxseed oil is rich in α-linolenic ● Hydrogenation is a commercial
acid, which has been shown to process in which hydrogen atoms
decrease blood pressure. are added to the double bonds in
● Rice bran oil is hypoallergenic and monounsaturated or polyunsaturated
rich in antioxidants such as fatty acids to make them more
tocopherols, tocotrienols, gamma saturated.
oryzanol, phytosterols, polyphenols, ● Too much hydrogenation,
and squalene. however, will cause the product to
become brittle and hard.

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● In addition to affecting plasticity, allows the lard to retain its shape at

hydrogenation contributes to making room temperature.
piecrusts flaky and puddings ● Interesterification is also used to
creamy. manufacture certain emulsifiers,
● Shortening keeps dough particles which are incorporated into
separate from each other, so that numerous processed foods to
after the fat melts during baking, the improve fat functionality
resulting pastry is flakey ● Interesterification is a commercial
process that rearranges fatty acids
on the glycerol molecule within
LARD, TALLOW, SUET
triglycerides so that they are more
heterogeneous, resulting in smaller
● Lard, which is the fat from swine, fat crystals and producing a
was the major shortening in use in smoother-consistency fat
the early 1900s.
● Tallow is also an animal fat, but it is
derived from beef cattle or sheep. COCOA BUTTER
● Suet is the solid fat found around
the kidneys and loin of beef and ● Cocoa butter originates from the
sheep. These animal sources of fat seeds of the Theobroma cacao
are primarily saturated. tree. Its melting point is just below
● They cannot be used for their body temperature, making it
shortening power in food perfect for “melt-in-themouth”
preparation without first being chocolate confections and candies.
rendered (melted down); for
commercial use, the rendered fat is
FAT REPLACERS
then deodorized.
● Antioxidants are often added to
lard to increase shelf life. ● Fat reduction affects important
● Lard produces poor textures in functional properties such as
cakes and icings; however, it makes flavor, appearance, texture,
excellent piecrusts. mouthfeel, handling, preparation,
and storage stability.

INTERESTERIFICATION
TYPES OF FAT REPLACERS

● Lard was largely replaced by the

shortenings that appeared on the ● The term fat substitute is often
market in the 1950s. Its usage used interchangeably with fat
increased again in the 1960s when replacer. However, replacer is a
the process of interesterification more general term describing any
was introduced. ingredient used to replace fat, which
● Certain fats, such as cocoa butter can include substitutes, mimetics
substitutes and lard, have (imitators), analogs, and extenders.
unacceptable textures until they ● Fat substitutes - Have physical and
are modified by interesterification. sensory properties identical to
● Lard is naturally too grainy and soft those of fats without the kcalories.
at room temperatures, but it They are often lipid-based, are
becomes extremely hard when stable at frying and cooking
refrigerated. temperatures, and replace the fat in
● Interesterification creates smaller foods on a weight-to-weight basis.
crystals in the lard, resulting in a ● Fat mimetics - “Mimic” the effects of
smoother texture with a slightly fat. These water-soluble, often
higher melting point. This change protein- or carbohydrate-based
ingredients replicate fat’s

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

creaminess and smoothness . They ● Lipid-Based Fat Replacers -

do not replace fat by weight, as do Chemically modifying the molecular
the fat-soluble substitutes and structure of fats can result in fat
extenders. replacers that have fewer kcalories
● Fat analogs - Have the than fat.
characteristics of fat but with fewer ● For example, short- and
kcalories because of their altered medium-chain fatty acids provide
digestibility. fewer kcalories than larger ones,
● Fat extenders - optimize fat which is why butyric acid (4 carbon
functionality so that less fat is atoms) yields fewer kcalories than
required. palmitic acid (16 carbons)

COMPOSITIONS OF FAT REPLACERS OLESTRA

● Fat replacers are made from a ● Olestra is a heat-stable, fat-based

variety of ingredients such as fat replacer used in snack foods
synthetic fats, microparticulated (crackers, potato chips, and tortilla
proteins, starch, fiber (cellulose, chips), fried and baked goods, and
gums, etc.), and even dried fruit dairy products.
puree ● Olean®. It is made from sugar and
● The synthetic fat replacers vegetable oil in a process in which
approved by the FDA are the 3-carbon glycerol molecule in
Simplesse® and olestra the oil is replaced by sucrose, which
● Carbohydrate-Based Fat can bond with 6, 7, or 8 fatty acids.
Replacers - Most of the fat This molecule is so large that it
replacers used by the food industry moves through the digestive tract
are based on carbohydrates. before enzymes have time to digest
- Fibers, gums, pectin, the fatty acids
cellulose, and starches ● Side effects of too much olestra
bind with water, swell, and consumption may include diarrhea,
impart some of the texture, cramps, and gas
mouthfeel, and opacity of fat
● Protein-Based Fat Replacers Milk
FOOD PREPARATION WITH FATS
- (whey) or egg proteins usually
serve as the source for
protein-based fat replacers. ● Very few fat replacers transfer heat
- These are often used in during food preparation the way fat
meats and other food can
products that have to be ● Oils used in deep-frying influence
refrigerated or frozen. the food’s flavor, texture,
- Simplesse® provides only appearance, nutrient value, and
one-seventh the number of shelf life
calories found in fat (11).
- It is made from the whey of FATS SUITABLE FOR FRYING
milk or from egg-white
proteins that have been
● Not every fat is suited for the very
reduced to tiny particles
high temperatures of deep-frying,
through a process called
which average 350 to 450°F (177 to
microparticulation
232°C).
- These protein droplets break
● The fats commonly used for frying
down when heated, so
must be 100% fat and heat stable,
Simplesse cannot be used in
so that they do not smoke or
baking or frying
develop rancid off-flavors

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

(vegetable oils and hydrogenated starts to bubble is very dangerous

shortenings). because it has reached its boiling
● The vegetable oils most frequently point
used include cottonseed, corn, ● Selecting fats with smoke points
canola, peanut, and safflower. above 420°F (216°C) for
● Soybean and canola oils are not commercial frying automatically
used because their omega-3 fatty olive oil, lard, and vegetable
acid content (7% and 10% shortenings.
linolenic acid, respectively) makes ● It may overheat and break down—
them susceptible to oxidative excludesthat is, decompose into
rancidity at the high temperatures glycerol and its individual fatty
of frying acids. The glycerol is further
● Butter as a sautéing fat to enhance broken down (hydrolyzed) to a
flavor, but the heat must be steel-blue smoke called acrolein.
carefully controlled because the Acrolein’s sharp, offensive odor
water and milk solids in butter cause warns people of its presence
it to spatter and burn more easily ● Hydrogenated shortenings with
● Margarine is not recommended for added monoglycerides and
frying because, in addition to diglycerides are not recommended
containing water, it has a low for frying
smoke point. ● Smoke point - the temperature at
which fat or oil begins to smoke,
due to the release of free glycerol,
SMOKE POINT
followed by the breakdown of
glycerol to acrolein
● Flash point - The temperature at
which tiny wisps of fire streak to
the surface of a heated substance
(such as oil).
- occurs when an oil is heated
to about 600°F (316°C)

● Fire point - the temperature at

which a heated substance (such as
oil) bursts into flames and burns
for at least 5 seconds

CONTROLLING THE TEMPERATURE

OF FRYING FATS

● Any egg yolks used in the coating

● Select fats with a high smoke point of battered foods also contribute to
— above 420°F (216°C) or higher the darkening effect on the fat.
— for frying. Further, the increased viscosity of
- This temperature is much overheated fat results in higher fat
higher than the boiling absorption rates in the fried foods,
point of water (212°F/100°C) making them greasy.
and even higher than frying ● The rapid deterioration of fat due
temperatures, which range to overheating is caused by
from 350 to 450°F (177 to polymerization
232°C)
● Fat boils at a much higher AVOIDING TOO-LOW TEMPERATURES
temperature than water, and fat that

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● Although it is important not to

overheat frying fats, it is equally
OPTIMAL FRYING TEMPERATURES
important not to let temperatures
drop too low because this may lead
to excessive fat absorption, ● The optimal frying temperature is
resulting in soggy, greasy fried 375°F (191°C),
food. ● Higher temperatures (375 to
● Temperatures quickly drop when 390°F/191 to 199°C) required for
large quantities of frozen food are smaller pieces of food
added to hot oil. ● Lower temperatures (350 to
● To combat this problem and help 365°F/177 to 185°C) for larger
stabilize the temperature, the food pieces of food
should be added in batches so that
the oil has sufficient time to reheat RECOMMENDED EQUIPMENT
to the correct temperature.
● It is also important that the food
● It is important to use stainless steel
pieces in a batch be the same size,
equipment; iron, and especially
so they finish cooking at the same
copper or copper alloys such as
time
brass, may increase rancidity.
● Deep, narrow containers are
recommended for deep-frying,
PERFECT BROWNING OF FRIED because shallow, wide pans
FOODS increase the surface area, lowering
the smoke point through greater
● If temperatures are correctly exposure to air.
controlled, the result will be a food ● The fryer should be filled no more
that has a crisp, golden crust than one-half to three-fourths full
surrounding a tender, perfectly of oil.
cooked interior ● Fresh fat should never be added to
● Fried foods cook on the principle fat that is rancid, foaming, or dark
that frying temperatures convert the because it will not overcome these
food’s water to steam, which then defects and will deteriorate very
escapes, keeping the food cool and quickly.
preventing it from burning and/or
absorbing fat. OPTIMAL FRYING CONDITIONS
● High-moisture foods such as
French fries need to be cooked at
● Many professional chefs claim that
lower temperatures, or the outside
foods fry best in oil that has been
will turn crispy before the inside
used at least once
has had a chance to cook.
● Desirable browned crusts occur
● Conversely, low-moisture foods
when oils pick up proteins and
need higher temperatures so they
carbohydrates from the foods that
will cook quickly, leaving no time
have been fried in them.
for the oil to enter the food.
● In addition, as the fat deteriorates,
● Determinants in temperature
the surface tension of the frying oil
selection to obtain the best crust
decreases, making foods more
color:
likely to soak up the fat
1. the amount of food
● Repeated use of a frying fat will
2. the length of time it is
also lower its smoke point
submerged in oil
because each heating hydrolyzes
3. the temperature of the food,
some of the triglycerides into
4. the oil quality
smaller molecules.
5. the food’s shape and size,
porosity, and type of coating

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

discarded. Generally, the oil

AVOID WATER
becomes darker and more viscous,
smokes easily, begins to have a
● Foods should be as free of surface rancid odor, and starts to impart
moisture as possible before being off-flavors to the foods fried in it.
submerged in the heated fat.
● Water causes spattering of hot oil,
which can cause burns; it requires
more energy to maintain
temperatures; it may result in longer
frying times; and it promotes
hydrolytic rancidity, which causes
the fat to break down chemically,
reducing its frying life.

COOL THE FRYING FAT

● These food particles should be

filtered out daily (or every 8 hours
of use), or they will darken the oil’s
color, lower its smoke point, and
reduce its keeping time.
● On the other hand, excessive
filtering introduces oxygen into the
oil, resulting in rancidity, gum
development, and foaming; the
latter is observed as a persistent FATS PREFERRED FOR HEALTH
layer of bubbles on the surface
● Consumers are advised to replace
REMOVE FOOD PARTICLES dietary solid (saturated or trans) fats
with monounsaturated and
polyunsaturated fats.
● A frying fat should theoretically stay
● Trans fats are the least desirable.
fresh for several months if it is
● Canola oil contains one of the
cooled immediately after use and
highest levels of
stored in an airtight container in a
monounsaturated fatty acids
dark, cool place
(58%)
● Large commercial fryers contain too
● Safflower oil scores highest in the
much fat to be cooled completely
polyunsaturated oil category.
and then efficiently reheated, so they
● Saturated fats such as coconut,
are turned down to approximately
palm, and palm kernel oils and
225°F (107°C).
butter should be avoided according
● Decreasing the temperature during
to certain dietary guides
downtime prevents the fat’s
● The fat in butter is primarily
breakdown and extends its
saturated, whereas that from
usefulness
margarine is more unsaturated.
● Lard, the unsaturated fat from
WHEN TO DISCARD THE USED swine is best replaced by vegetable
FRYING FAT? shortening, but even the latter is
partially saturated
● There is no easy method for
determining when oil that has been
used repeatedly should be

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● Shortenings and most oils are

usually
● stored at room temperature and
should be kept tightly covered in a
dark spot on the cupboard shelf;
however, they are best refrigerated
because they will keep longer.
● Olive oil has a shorter shelf life
than most vegetable oils and should
be refrigerated fairly soon after
opening.
● Monounsaturated fats such as
olive oil
● usually keep for about 1 year.

REDUCING FAT BY HEALTHY

METHODS

● All of the moist and dry-heat cooking

methods, with the exception of
frying, lend themselves to fat-free
preparation of foods
● Dietary fat intake may also be
lowered by selecting a cooking
method that does not rely on fat
● Sautéing and stirfrying - is
acceptable if the right type of fat is
chosen and a minimal amount is
used
● Pan-frying and deep-frying - is
essentially impossible to lower the
amount of fat used.

RANCIDITY
STORAGE OF FATS

● Rancidity is the chemical

● Fats such as butter and margarine
deterioration of fats, which occurs
are best stored in the refrigerator.
when the triglyceride molecule
● Butter will keep for months in the
and/or the fatty acids attached to
freezer, but margarines do not
the glycerol molecule are broken
freeze as well because their
down into smaller units that yield
emulsions may separate under such
off-flavors and rancid odors.
conditions.

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN

ND735 - BASIC FOODS 2 LECTURE FINALS PERIOD

● The longer a fat is stored, the unstable molecules called

greater the possibility of its free radicals
becoming rancid. - Free radicals contribute to
● Fats and oils used in cooking tend to the further breakdown of
become rancid because they are fats into smaller compounds,
exposed to oxygen, heat, and light resulting in unpleasant
odors and off-flavors
TYPES OF RANCIDITY
FLAVOR REVERSION
● Hydrolytic Rancidity - fats become
rancid when exposed to water, ● Flavor reversion, a type of
usually the water found frozen on characteristic flavor change that
food to be fried. occurs even before actual rancidity
- The addition of water begins.
hydrolyzes the bonds in the - The breakdown (oxidation)
triglyceride, causing it to of α-linolenic acid, an
break down into smaller essential fatty acid found in
compounds, certain vegetable oils,
- The released fatty acids have leading to an undesirable
an unpleasant aroma and flavor change prior to the
taste start of actual rancidity
- Placing cold, wet food in
heated frying oil introduces
water, making the oil prone
to hydrolytic rancidity
- Conversely, fats that have
not been heated are more
prone to hydrolytic rancidity
because the lipase enzymes
have not yet been destroyed
by heat.

● Oxidative Rancidity - Fats can also

become rancid when they are
exposed to the oxygen in air
because oxygen is taken up at the
double bonds of an unsaturated
fatty acid.
- The higher the degree of
unsaturation, the more likely
it is that the fat will be subject
to oxidative rancidity
- Fats containing omega-3
fatty acids are particularly
susceptible, and the problem
is magnified at high
temperatures, such as those
used in frying.
- Oxygen atoms attach to the
carbons next to the double
bond of the fatty acid,
creating very reactive and

UNDERSTANDING FOOD PRINCIPLES AND PREPARATION AMY BROWN