Ozone in Food Processing Applications
Past Experience, Future Potential and Regulatory Issues:
Zentox Corporation
Abstract
The recent stories of food contamination reported in the media serve to highlight the need
for the food industry in the United States to seek better, more effective methods of
ensuring the safety of food products. In the vast majority of cases reported, the culprits
have been identified as Escherichia coli, Salmonella enteriditis, Listeria monocytogenes
and other pathogens found in fruits, meats, shell fish and other foods consumed by the
public. The results of these cases of contamination have been serious illnesses and, in
some
cases, fatalities.
The use of ozone in the processing of foods has recently come to the forefront as a result
of the recent approval by the U.S. Food and Drug Administration approving the use of
ozone as an anti-microbial agent for food treatment, storage and processing. The FDA
approval marks a watershed event for the food industry. Prior to the approval, FDA had
approved ozone for use only as a disinfection mechanism for bottled water production
and the sterilization of bottled water lines. The recent regulatory breakthrough is a result
of efforts made by the Electric Power Research Institute (EPRI) and the panel of
technical experts assembled to review and evaluate the efficacy and safety of ozone in
food processing.
It is worthy of noting that, the use of ozone in food processing has been allowed and
accepted in Japan, Australia, France and other countries for some time. There is a
plethora
of documentation and supporting literature attesting to the benefits of ozonation as a food
product sterilization methodology some of which will be reviewed herein.
The FDA’s recent approval serves to provide the basis for expanded use of ozone in
food processing with application ranging from produce washing to recycling of poultry
wash water to seafood sterilization. A sampling of these applications will be presented in
the attached case studies.
The 1997 EPRI Expert Panel Report
This important reference document is organized as follows: An Executive Summary that
is followed by chapters dealing with Efficacy of Ozone, Applications of Ozone, Safety
Issues and Ozone Toxicology, Nutrient Impacts of Ozone and Summary Options of the
Expert Panel. Also
within the EPRI document are various appendices containing the qualifications of the
experts, abstracts and citations of pertinent articles dealing with the use of ozone in
processing and preserving foods. Specific applications are divided into 37 categories
including; treatment, disinfection, eggs, fish, fruits, meats, poultry, vegetables, storage,
etc.
Introduction
Ozone, first discovered in 1840 (Schonbein), began being utilized as a disinfection agent
in
the production of potable water in France in the early 1900’s. The majority of early
development was limited to Europe where it became more widely used in drinking water
treatment. The potential utility of ozone to the food industry lies in the fact that ozone is
52% stronger than chlorine and has been shown to be effective over a much wider
spectrum of microorganisms than chlorine and other disinfectants. Complementing the
effectiveness, is the fact that ozone, unlike other disinfectants, leaves no chemical
residual
and degrades to molecular oxygen upon reaction or natural degradation. The fact that
ozone has a relatively short half-life is both an asset and a liability to practitioners. This is
particularly true in treatment of drinking water where ozonation is employed to enhance
filtration and provide primary disinfection but requires the addition of chlorine as the
terminal disinfectant to maintain a residual in the distribution system.
Ozone is effective killing microorganisms through oxidation of their cell membranes and
most of the pathogenic, foodborne microbes are susceptible to this oxidizing effect.
During food processing operations, surface disinfection of the product (raw or partially
processed) is very important. This is supported by the following statistics:
1. An estimated 30% of fresh produce is lost by microbial spoilage from the time of
harvest, through handling, storage, processing, transportation, shelving and delivery to
the
consumer (Beuchat 1991).
2. The USDA estimates the costs associated with foodborne illness to be in the range of $
5.5 billion to $ 22 billion per year.
History of Early Ozone Applications in Food Processing:
Some early reported uses of ozone in food processing and preservation have been
reported and documented. The examples below represent a sampling of notable cases:
1. Fish and Shellfish Preservation:
Washing of fish with ozonated water extended shelf life for 5 days:
Experiments performed by Violle in 1929 found that ozonated seawater spiked with
various strains of bacteria (B. typhus, B. coli, etc.) resulted in sterilization that was
comparable to what
was obtained in fresh water. Further experiments showed that exposure of shellfish to
ozonated water did not adversely affect the taste or appearance of the shellfish. Thus,
Violle concluded that preozonation of water was suitable treatment for depuration of
shellfish. Later work by Salmon and Le Gall (1936) built upon the work of Violle and
reported that fresh fish, stored under ozonated ice, were edible for between 12 and 16
days. Fish treated with sterilized ice (presumably hypochlorous acid treated) were
inedible after the 12th day and, possibly after the 8th day.
The original work in this area was carried further by others and reportedly resulted in the
installation of an ozone system designed to sterilize 2000 kg per day in Le Havre and
another facility in Boulogne-sur-Mer for treating a daily output of 6000 kg.
2. Ozone Used in Cold Storage for Meats:
Gaseous ozone was used as a preservation agent in meat and egg storage:
Kuprianoff (1953) reported that the first known use of ozone as a food preservation agent
was in Cologne, Germany dating back to 1909. Later industrial applications using gas
phase ozone for food preservation were reported in 1924 where Hartman stated that “in
cold storage ozone is successfully used to prevent the growth of fungi” and “ eggs have
been carried at a relative humidity of 88 and 90 percent and mold developments
inhibited with the use of ozone”. Hartman summarized by noting that ozone “has
manifold applications in cold storage and splendid results are being obtained in practice
with this reagent every day”.
3. Disinfection and Preservation of Fruits and Vegetables:
One of the earliest reported experiments dealing with preservation of fruits was related to
ozonation of bananas (Gane - 1933, 1934, 1935, 1936). Since then, numerous studies
have been conducted on a wide variety of fruits and vegetables including carrots,
broccoli,
pears, peaches and apples. The vast majority of these studies have reported some degree
of shelf life extension and reduction of pathogenic contamination.
Recent Studies of Ozonation in Food Processing:
In spite of past regulatory restriction limiting usage of ozone in the U.S. food processing
industry, numerous studies were undertaken to determine the efficacy and economics of
ozonation. The examples below serve to illustrate some of these studies and conclusions.
1. Fruits and Vegetables:
Several controlled studies have been reported in the food science literature relating to the
evaluation of treatment of fruits and vegetables with ozonated water. Kondo et al (1989)
observed greater than 90% reduction of total bacterial counts upon treatment of Chinese
cabbages with ozonated water (2.3 mg/L) for 60 minutes.
Treatment of wash water used in processing of carrots has been reported to provide 3 log
reduction of bacteria (Williams et al 1995).
Barth et al (1995) evaluated ozone exposure for prevention of fungal decay on thornless
blackberries. The fruit was harvested and stored for 12 days at 2 deg. C in 0.0, 0.1 and 0.3
ppm ozone, then evaluated for fungal decay (Botrytis cinerea), anthocyanines, color and
peroxidase activity. Ozone storage suppressed fungal development for 12 days, while
20%
of control fruits showed decay. The treated fruit did not show observable injury or
defects.
Sarig et al (1996) showed that ozone at low dosages (0.1 mg/g fruit) for 20 minutes,
reduced the levels of fungi yeasts and bacteria on grapes, but that higher doses caused
some fruit damage.
2. Poultry:
The poultry processing industry is a large volume consumer of water. The potential for
reuse of poultry processing water represents an attractive economic benefit to the
industry. In 1996 the USDA approved the use of ozonation for washing of poultry
carcasses (provided that the ozone did not come into direct contact with the product).
Studies by Chang and Sheldon (1989) reported that a combination of screening,
diatomaceous earth filtration and ozonation yielded the highest quality of water with total
microbial loads (total coliforms, E. coli and salmonella reduced by 99%). A subsequent
study, Chang and Sheldon (1989) found no significant differences in measures of carcass
quality including skin color, taste or shelf life using recycled, ozone treated water as
opposed to fresh makeup water. The investigators further reported that a 2.7 log reduction
in of total plate count was observed in the recycled water stream. The results of this study
showed that, for a typical broiler processing plant (240,000 broilers/day) the savings
resulting from chiller water reuse would equate to 50% reduction in discharges and
savings of more than $ 45,000 per year.
3. Extension of Food Product Storage Life:
The following are a sampling of studies directed at application of gaseous ozone in food
storage facilities.
A 1980 study (Gabriel’yants’) showed that cheese stored with periodic ozonation
prevented mold growth for 4 months while controls showed mold growth as soon as 1
month.
Japanese researchers indicated good results in the treatment of grains, flour and raw
noodles with ozone with significant reductions in microbial growth.
Dondo et al (1992) reported that ozone treatment during refrigerated storage stabilized
the surface bacteria count on beef and reduced that on fish.
Naitoh (1989) showed that ozone treatment inside a confectionery factory reduced
airborne microorganisms over a 1 - 1.5 year period, “remarkably” inhibited bacterial
growth and extended storage life of the product by 7 days.
4. Ozone Treatment of Dye Wastewater
Several studies have shown ozone and ozone/hydrogen peroxide to be effective in
removal
of color resulting from dye processing. Dyes used in food processing are typically easier
to
oxidize with ozone since they are organically based compounds.
Discussion of Current and Future Applications
Ozone is by no stretch a panacea or universal solution for all food processing operations.
There are a significant number of good, sound applications including; disinfection of
food
wash water, wastewater treatment and recycling, treatment of cooling water and process
water, and gas phase sterilization of products in storage and transport. Along with these
beneficial applications comes some limitations. There are existing restrictions relating to
human exposure to ozone (OSHA and EPA) which must be considered. Plant operators
seeking to employ ozone will be faced with system design and process operation
challenges.
Proliferation of ozone applications in the food industry is assured. As of this writing, the
industry is free to start using ozone. Operators wishing to apply ozone are expected to
employ Good Manufacturing Practices to protect workers from inadvertent exposure to
ozone as well as to avoid overuse of ozone which may cause damage to the food product.
Conclusions
As a result of the recent FDA ruling, it is anticipated that ozone in food processing will
be
accelerated due to a number of factors:
1. The use of chlorine by the U.S. food industry is coming under increasing
scrutiny by regulators due to toxicity issues and disinfection byproducts (DBPs).
2. Ozone has been proven to produce greater lethality rates for microorganisms
than chlorine or other chemical sanitizing agents.
3. The recent surface water rules promulgated by the U.S. EPA relating to chlorine
and chlorine derived DBPs will undoubtedly stimulate operators to seek
technologies which will assure discharge compliance.
4. The increasing cost of water resources (both makeup and discharge), together
with the drive toward more conservation, will stimulate industry to seek
treatment methods which allow recycling of product wash water and
process water.
5. Advances in ozone generation and applications technologies have continued to
make the process more reliable and economical.
