U.S. patent application number 10/784351 was filed with the patent office on 2004-08-26 for surface decontamination of frankfurters and other cooked sausage and processed meat and poultry products.
This patent application is currently assigned to STERIS INC. , a Delaware corporation. Invention is credited to Greszler, Alan J., Krieger, Eric W., Marsden, James L., Sanford, Bill R., Schwartz, Lewis I..
Application Number | 20040166216 10/784351 |
Document ID | / |
Family ID | 32716669 |
Filed Date | 2004-08-26 |
United States Patent
Application |
20040166216 |
Kind Code |
A1 |
Marsden, James L. ; et
al. |
August 26, 2004 |
Surface decontamination of frankfurters and other cooked sausage
and processed meat and poultry products
Abstract
Food products, such as precooked meats, raw meats, and poultry
are treated with a decontaminant solution to remove surface
microorganism contamination. The decontaminant solution contains
peracetic acid at a concentration of from about 100 to 4000 ppm and
has broad spectrum activity against a variety of pathogenic and
spoilage microorganisms, such as Listeria monocytogenes.
Inventors: |
Marsden, James L.;
(Manhattan, KS) ; Krieger, Eric W.; (Mentor,
OH) ; Schwartz, Lewis I.; (Shaker Heights, OH)
; Greszler, Alan J.; (Elyria, OH) ; Sanford, Bill
R.; (Willoughby, OH) |
Correspondence
Address: |
Thomas E. Kocovsky, Jr.
FAY, SHARPE, FAGAN, MINNICH & McKEE, LLP
Seventh Floor
1100 Superior Avenue
Cleveland
OH
44114-2518
US
|
Assignee: |
STERIS INC. , a Delaware
corporation
Temecula
CA
92590
|
Family ID: |
32716669 |
Appl. No.: |
10/784351 |
Filed: |
February 23, 2004 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10784351 |
Feb 23, 2004 |
|
|
|
09616516 |
Jul 14, 2000 |
|
|
|
60143892 |
Jul 14, 1999 |
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Current U.S.
Class: |
426/326 |
Current CPC
Class: |
A23L 3/349 20130101;
A23L 3/42 20130101; A23B 4/033 20130101; A23L 3/3508 20130101; A23L
13/65 20160801; A23B 4/30 20130101; A23B 4/20 20130101; A23L 13/62
20160801; A23L 3/3499 20130101 |
Class at
Publication: |
426/326 |
International
Class: |
A23K 001/00 |
Claims
Having thus described the preferred embodiment, the invention is
now claimed to be:
1. A method of treating a food product comprising: contacting an
exterior of the food product with a decontaminant solution
containing an antimicrobial agent which includes peracetic acid for
a sufficient time to microbially decontaminate the exterior of the
food product.
2. The method of claim 1, further including: rinsing the
microbially decontaminated food product to remove the decontaminant
solution.
3. The method of claim 1, further including: sterile drying the
decontaminated food products.
4. The method of claim 1, wherein the peracetic acid in the
decontaminant solution is at a concentration of from about 100 to
about 4000 ppm.
5. The method of claim 1, wherein the peracetic acid concentration
is from about 1000 to about 2000 ppm.
6. The method of claim 1, wherein the step of contacting the food
product with the decontaminant solution includes spraying the
decontaminant solution over the food product.
7. The method of claim 6, wherein the food product is sprayed with
the decontaminant solution for a period of from about 10 seconds to
5 minutes.
8. The method of claim 7, wherein the food product is sprayed with
the decontaminant solution for a period of from about 1 to 2
minutes.
9. The method of claim 6, wherein the step of contacting the food
product with the decontaminant solution includes transporting the
food product on a conveyor past spray nozzles which spray the
decontaminant solution over the food product.
10. The method of claim 6, further including: recirculating the
sprayed decontaminant solution.
11. The method of claim 1, wherein the food product comprises hot
dogs and the method further includes, prior to the step of
contacting the exterior of the food product: removing the hot dogs
from casing skins.
12. The method of claim 3, further including, after the step of
drying the food product: aseptically packaging the food
product.
13. A method of treating a food product comprising: a) spraying the
food product with a solution comprising peracetic acid in a first
chamber; and b) drying the food product in a second chamber.
14. The method of claim 13, further including: c) after step a),
rinsing the food product with a rinse fluid in a third chamber
intermediate the first and second chambers.
15. The method of claim 13, further including: conveying the food
product through the first and second chambers on a conveyor
system.
16. An apparatus for treatment of a food product comprising: a
first chamber; spray nozzles disposed in the first chamber for
spraying a decontaminant solution over the food product, the
decontaminant solution including peracetic acid; a source of the
decontaminant solution; a pump fluidly connected with the source of
the decontaminant solution and the nozzles for supplying
pressurized decontaminant solution to the nozzles; a second
chamber; a source of a drying gas connected with the second chamber
for drying the decontaminated food product; and a conveyor system
which conveys the food product through the first and second
chambers.
17. The apparatus of claim 16, further including: a third chamber
intermediate the first and second chambers, the conveyor system
conveying the food product through the third chamber; a source of a
rinse fluid connected with the second chamber which delivers a
rinse fluid to the second chamber for rinsing the decontaminated
food product.
18. The apparatus of claim 16, further including: a recirculation
system which recirculates the sprayed decontaminant solution to the
nozzles.
Description
[0001] This application claims the priority of U.S. Provisional
Application Serial No. 60/143,892, filed Jul. 14, 1999.
BACKGROUND OF THE INVENTION
[0002] The present invention relates to the food processing arts.
It finds particular application in conjunction with the
post-pasteurization, surface microbial decontamination of hot dogs,
sausages, and other processed meat and poultry products prior to
packaging, and will be described with particular reference thereto.
It should be appreciated, however, that the invention is also
applicable to the treatment of raw meat and poultry and other food
products subject to microbial contamination.
[0003] Prevention of food poisoning is of paramount importance in
the food processing industry. Concern for food safety has lead most
countries to regulate the food industry heavily to minimize public
health risks. Despite these efforts, food poisoning still occurs.
Many instances of food poisoning are attributed to bacteria, such
as Salmonella, Clostridium, and Staphylococcus, among others.
[0004] Of rising concern is the relatively recent increase in the
Listeria contamination of poultry and processed food products, such
as frankfurters, other sausages, cheese, dairy food, and seafood.
Processed meat and poultry products such as frankfurters are
generally cooked to destroy harmful bacteria. Of particular concern
is the discovery that pasteurized and fully cooked processed foods
are being contaminated with microbes, such as Listeria
monocytogenes, following cooking or pasteurization and prior to
packaging for point of sale. Such contamination is typically
surface contamination and is believed to be caused by the contact
of microbes with food surfaces subsequent to heat treatment.
Microbes such as Listeria may be airborne (i.e, carried by dust) or
present on food contacting surfaces, such as processing
equipment.
[0005] Recently, several outbreaks of food poisoning have been
reported in which the causative agent was suspected to be or
identified as Listeria contaminated food. Listeriosis is a serious
disease which may cause meningitis, spontaneous abortion, and
perinatal septicaemia. Although treatable with early diagnosis,
untreated Listeriosis exhibits a high mortality rate. In 1998, 20
deaths were associated with a Listeria epidemic. Regulations now
specify that food should be absolutely free of Listeria, any
contamination is considered to be an adulteration and the food
should not be placed in commerce.
[0006] Food preservation by inhibition of growth of Listeria
monocytogenes is difficult. Listeria is a particularly difficult
microorganism to destroy because it is heat resistant and is able
to grow even under refrigeration in raw and cooked products.
Methods for destroying the organism on raw and on processed foods
have included treatments using heat, radiation, chemicals, or
antibiotics.
[0007] In the heat and irradiation treatments, the food products
are subjected to the heat or radiation after packaging. However,
the heat resistance of the organism makes it difficult to achieve
complete kill through heat.
[0008] Antibiotics, such as Streptococcus lactis-derived or
synthetic equivalent bacteriocin, such as nisin, have been used,
either as a spray, or dip, or as a film on the packaging or casing
which remains in contact with the food during heat treatment.
[0009] Chemicals used in treating the food products include
ammonium compounds and acids such as citric, lactic and acetic
acid, which have been used to wash down meat carcasses. With the
chemical treatment methods, the carcass is placed on a conveyer
system and the decontaminating chemical is sprayed over the items
as they pass beneath. Liquid smoke has been used on pasteurized
processed foods to inhibit recontamination after cooking. However,
this imparts an undesirable, phenolic taste when used
post-pasteurization.
[0010] If chemicals are to be used post-pasteurization, it is
desirable that they are both effective antimicrobial agents and
non-hazardous to consumers if they remain on the food product.
Acids such as citric, lactic and acetic acids, while being safe for
consumers, are not always completely effective at inactivating the
microorganism. Even if one or two microorganisms remain on the food
product, these can grow and multiply under refrigeration to a level
to which they are toxic to the consumer by the time the product is
sold.
[0011] The present invention provides for a new and improved
apparatus and method for treating food products which overcomes the
above-referenced problems and others.
SUMMARY OF THE INVENTION
[0012] In accordance with one aspect of the present invention, a
method of treating a food product is provided. The method includes
contacting an exterior of the food product with a decontaminant
solution containing an antimicrobial agent, which includes
peracetic acid, for a sufficient time to microbially decontaminate
the exterior of the food product.
[0013] In accordance with another aspect of the present invention,
a method of treating a food product is provided. The method
includes spraying the food product with a solution comprising
peracetic acid in a first chamber and drying the food product in a
second chamber.
[0014] In accordance with another aspect of the present invention,
an apparatus for treatment of a food product is provided. The
apparatus includes first and second chambers. Spray nozzles are
disposed in the first chamber for spraying a decontaminant solution
over the food product. The decontaminant solution includes
peracetic acid. A pump is fluidly connected with a source of the
decontaminant solution and the nozzles for supplying pressurized
decontaminant solution to the nozzles. A source of a drying gas is
connected with the second chamber for drying the decontaminated
food product. A conveyor system conveys the food product through
the first and second chambers.
[0015] One advantage of the present invention is that pathogenic
bacteria, such as Listeria, E. coli, and Salmonella are destroyed
in a short period of time.
[0016] Another advantage of the present invention is that the
peracetic acid used to decontaminate the food products naturally
degrades to non-harmful reaction products, such as acetic acid and
water, over a short period of time.
[0017] Still further advantages of the present invention will
become apparent to those of ordinary skill in the art upon reading
and understanding the following detailed description of the
preferred embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0018] The invention may take form in various components and
arrangements of components, and in various steps and arrangements
of steps. The drawings are only for purposes of illustrating a
preferred embodiment and are not to be construed as limiting the
invention.
[0019] FIG. 1 is a schematic top view of a food treatment system
according to the present invention;
[0020] FIG. 2 is a schematic side sectional view of the food
treatment system of FIG. 1;
[0021] FIG. 3 is a schematic front view of the food treatment
system of FIG. 1; and
[0022] FIG. 4 is a perspective view of a system for treatment of
carcasses.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0023] A decontaminant solution containing peracetic acid has broad
spectrum antimicrobial activity for treatment of exposed surfaces
of processed foods and raw meats and poultry. While particular
reference is made to the reduction in the species Listeria
monocytogenes on cooked sausages, such as frankfurters, it should
be appreciated that the decontaminant solution is also effective
for the reduction in other pathogenic and spoilage microorganisms,
such as Aeromonas hydrophila, Aerobacter butzleri, Bacillus cereus,
Campylobacter jejuni, Eschericia coli, Salmonella typhimurium,
Staphylococcus aureus, and others on a variety of processed foods
and raw meats and poultry. The term "decontaminate" and similar
terms are used herein to encompass all forms of surface microbial
decontamination, including disinfection and sterilization.
[0024] With reference to FIGS. 1-3, a system for treatment of food
products to remove surface contamination of microorganisms, such as
Listeria, includes a conveyor system 10, such as a moving conveyor
belt. Food products to be treated 12, such as precooked meats,
sausages, or other processed foods, raw meat, poultry, fish, whole
carcasses, or dairy products are loaded onto the conveyor belt at
position A. In the case of sausages, such as frankfurters, these
are preferably removed from their casing by peeling or other method
prior to loading onto the conveyor system. The peeled frankfurters
pass from the peeler to an orienting machine (not shown) which
loads them on to the conveyor such that they are oriented
perpendicularly to the direction of travel. While FIGS. 1-3 show
the food products hanging from the conveyor on hooks 14, it is also
contemplated that the food products be laid on a perforated
conveyor belt 10 and rotated during conveyance.
[0025] The conveyor system 10 carries the food products into a
first chamber or enclosure 20, where the food products are sprayed
with the decontaminant solution. Preferably, the conveyor system
then carries the sprayed food products into a second chamber or
enclosure 24 where a rinse fluid is sprayed over the food products.
Finally, the food products are carried by the conveyor into a third
chamber or enclosure 26 where sterile air is blown over the
products to dry them. The food products are aseptically removed
from the conveyor at point B and packaged in sterile packaging for
shipment.
[0026] Multiple spray nozzles 30 in the first chamber 20 spray the
decontaminant solution over the food products. The spray nozzles
are preferably arranged so that all surfaces of the food products
are contacted with the decontaminant solution. The spray nozzles
may be arranged at the sides, above, and or below the processed
food passing by. Alternatively, or additionally, the conveyor
system 10 rotates the food products as they pass by the nozzles 30
so that all surfaces are contacted.
[0027] A pump 40 pumps the decontaminant solution from a reservoir
42 to the spray nozzles through a supply line 44. Sprayed
decontaminant solution drips through openings 48 in the conveyor
system and collects in a sump 50 at the base of the chamber 20.
Preferably, the pump withdraws the collected decontaminant solution
from the sump through a return line 52 and recycles it through the
spray nozzles 30.
[0028] Periodically, the decontaminant solution is replaced or
replenished with fresh decontaminant solution from the reservoir 42
and the used decontaminant is carried to a drain or otherwise
disposed. Additionally, or alternatively, a sensor 54 detects the
peracetic acid concentration of the circulating decontaminant
solution. A controller 56 receives signals from the sensor. When
the peracetic acid concentration drops below a predetermined level,
the controller causes additional peracetic acid to be supplied from
the reservoir 42 to raise the peracetic acid concentration in the
decontaminant solution flowing to the nozzles.
[0029] The second chamber 24 is similar to the first chamber except
in that a rinse fluid is sprayed over the food products in place of
the decontaminant solution to remove substantially all of the
peracetic acid from the food products. Specifically, a second pump
60 pumps the rinse fluid through a supply line 62 to nozzles 64 in
the second chamber. The sprayed rinse fluid passes through
apertures 66 in the conveyor system and collects in a sump 68 at
the bottom of the second chamber. The sprayed rinse fluid is
returned to the pump by a return line 70. Alternatively, the return
line directs the sprayed rinse fluid directly to a drain 72.
[0030] Preferably, the rinse fluid comprises sterile water which is
free of all harmful microorganisms. A source of sterile water 74,
such as a sterile water generator, preferably receives tap water
and destroys harmful bacteria in the water. The sterile water is
then pumped from the source 74 to the supply line 62 by the pump
60.
[0031] In the third chamber 26, an air manifold 80 blows sterile
air over the food products to dry them. The air is generated by an
air dryer 82 which passes the dry air to the manifold via a forced
air inlet line 84. Air is returned from the chamber to the air
dryer though an air return line 86 where it is dried and
sterilized, such as by heating, and then cooled to an appropriate
temperature prior to returning the air to the manifold 82.
[0032] The three chambers are aseptically connected with each other
by conduits 90, 92 such that microorganisms are inhibited from
recontaminating the food between the three stages. While 3 separate
chambers are shown, it is also contemplated that the
decontaminating and rinsing steps may be carried out in a single
chamber, with the rinse nozzles 64 spaced a suitable distance from
the decontaminant spray nozzles 30 so that there is little or no
interference between the respective spray jets. While the air
drying step may also be performed in the same chamber as the
decontaminant and rinsing steps, it is preferable to perform this
step in a separate chamber, where humidity can be reduced.
[0033] Optionally, the rinse step and rinse chamber are eliminated.
The peracetic acid in the decontaminant solution rapidly degrades
over a period of a few hours to non-harmful products, such as
acetic acid and water, and thus traces of the decontaminant
solution on the food products are not harmful to consumers. Acetic
acid (vinegar) is a common additive in many food products and is
not harmful. Leaving a portion of the decontaminant solution on the
food products ensures that they remain microbially decontaminated
until packaging. The decontaminant solution also helps to keep the
interior of the package sterile during packaging. Any remaining
peracetic acid in the package degrades to harmless products by the
time packaged food products reach the store shelves or the ultimate
consumer.
[0034] It should be appreciated that the decontaminant solution is
also suited to other methods of treatment of food products, such as
dipping or immersing in the solution.
[0035] The decontaminant solution preferably contains from about
500 to about 4,000 ppm of peracetic acid. The optimal concentration
depends on the length of time to which the food products are
exposed to the decontaminant solution and on the temperature of the
decontaminant solution. For example, a six log reduction (a
reduction in the number of microorganism of a factor of 10.sup.6)
can be achieved by contacting the surfaces of the food product with
a 1,000 ppm peracetic acid solution for 12 seconds at 8.degree. C.
For ensuring complete elimination of resistant microorganisms, such
as Listeria, longer times and/or higher peracetic acid
concentrations are preferred. Preferred peracetic acid
concentrations are from about 1000 to about 2,000 ppm for contact
times of 30 seconds to 1 minute to ensure complete kill of Listeria
and other undesirable microorganisms at temperatures of from about
8-20.degree. C. Microbiological analysis procedures are carried out
periodically on samples of the treated frankfurters to ensure that
the conditions used are maintaining a 100% kill of Listeria or
other selected microorganisms.
[0036] Tests with a variety of microorganisms have shown that the
peracetic acid decontaminant solution has broad spectrum activity
against a wide variety of pathogenic and spoilage microorganisms.
Minimum inhibitory concentrations can be readily established for
any specific microorganism or microorganisms to be destroyed.
[0037] The decontaminant solution may also contain other
components, such as buffers, surfactants, chelating or sequestering
agents, and the like, provided that these are non-toxic (i.e.,
specified as "food grade") or are rinsed thoroughly from the food
products prior to packaging.
[0038] The peracetic acid for the decontaminant solution may be
diluted from a concentrate, such as a 30-38% peracetic acid in
water concentrate. In one preferred embodiment, the concentrated
peracetic acid is metered into the reservoir using a metering
device, such as a metering pump 100. Or, the concentrated peracetic
acid is provided as a measured dose. For example, a measured dose
of the liquid concentrate is contained in a cup. The cup is opened,
when needed, to release the contents into a dilution liquid, such
as water. Optionally, the cup contains two or more compartments,
with the liquid concentrate contained in one compartment and one or
more of the other components of the decontaminant solution, such as
buffers, surfactants, corrosion inhibitors, etc., contained in a
separate compartment or compartments. The compartments are opened
when the decontaminant solution is to be used, either by the user,
or by an automated opening device.
[0039] In an alternate embodiment, the decontaminant solution may
be formed by reaction of two or more reagents which form the
peracetic acid in water. For example, an acetyl donor, such as
acetyl salicylic acid, and a persalt such as a perborate are mixed
in water, where they react to form the peracetic acid. In one
embodiment, acetyl salicylic acid and sodium metaborate are
separately contained in a two compartment cup, optionally together
with other dry components of the decontaminant solution. The cup is
opened and the contents of the two compartments are mixed with a
known quantity of water in the reservoir 42 to form the
decontaminant solution.
[0040] In yet another alternate embodiment, peracetic acid is
generated electrolytically and supplied to reservoir 42.
[0041] The water for the decontaminant solution may be tap water or
treated water, such as distilled, filtered or sterile water.
Optionally, all or part of the water may be replaced by other
solvents.
[0042] The terms "chelating agents" and "sequestering agents" are
used synonymously herein to encompass inorganic and organic
compounds capable of forming coordinating complexes with metals.
Suitable chelating agents include, but are not limited to, ethylene
diaminetetraacetic acid and its salts, cyclodextrins,
hydrocarboxylic acids, such as citric acid; acetic acid, lactic
acid, tartaric acid, and their salts, alone or in combination.
[0043] The decontaminant solution may also contain other
antimicrobial decontaminants, such as hydrogen peroxide, citric
acid, lactic acid, or acetic acid, alone, or in combination.
[0044] A preferred pH for microbial decontamination by the
peracetic acid is around neutral. Accordingly, the pH of the
decontaminant solution is preferably adjusted or buffered to a pH
of between about 6.5 and about 7.5. Phosphate buffer systems, which
are acceptable in food processing, are suitable buffers.
[0045] With reference to FIG. 4, an alternative embodiment of the
apparatus of FIGS. 1-3 suitable to the treatment of meat carcasses
is shown. A conveyor system 120 has a series of hooks 122 on which
the carcasses are hung. The conveyor system carries the carcasses
through a spray 124 system similar to a car wash in which the
decontaminant solution is sprayed over the carcasses. As shown in
FIG. 4, an inverted U-shape supply line 126 carries the
decontaminant solution from a reservoir 128 to a variety of spaced
nozzles 130, via a pump 132. The nozzles spray the decontaminant
fluid over the carcasses. Sprayed decontaminant solution drips from
the carcasses and is collected in channels 134 and returned to the
reservoir supply or passed to a drain. Optionally, similar spray
nozzles 140 spray a rinse fluid, such as sterile water, over the
carcasses.
[0046] For treating whole animals, the anti-microbial solution
(described above) may be applied to the food animal after stunning,
but before the animal is bled. In cases where a de-hairing or a
de-feathering technology is applied, the application of peracetic
acid, preferably occurs after the stunning and after the de-hairing
or de-feathering processes, but before the animal is bled. Multiple
spray nozzles are used in a specialized chamber designed to
accommodate the species of food animal which will be treated. The
chamber is designed to apply the anti-microbial solution to the
entire surface of the animal and may be unique to each species of
food animal (i.e., bovine, porcine, ovine, avian).
[0047] For animal carcass decontamination, the anti-microbial
solution is applied to the food animal carcass after stunning,
de-feathering or de-hairing, and when applicable, after the removal
of the hide or skin. The application utilizes multiple spray
nozzles and, as for whole animal treatment, occurs in a specialized
chamber designed to accommodate the species of food animal carcass.
Preferably, the carcass is treated at multiple stages of the
slaughter process, including pre-evisceration, immediately
post-evisceration, and before and after the application of other
anti-microbial technologies. These may include hot water washes,
organic acid rinses (lactic acid, acetic acid or citric acid),
steam vacuuming, and steam pasteurization.
[0048] The treatment may also be applied to decontaminate heads,
organs, offal and other carcass parts. The concentration of the
anti-microbial solution, contact time, temperature and other
application parameters are controlled to optimize the effectiveness
of the treatment.
[0049] In an alternative embodiment, the food products or carcasses
are dipped into the decontaminant solution in place of being
sprayed. The decontaminant solution may be contained in a bath and
the food product immersed in the solution for a period of from
about five seconds up to about one minute, or more, depending on
the concentration of the peracetic acid used. The decontaminated
food products may then be rinsed, either by spraying a rinse
solution over the food products or by immersing the food products
in a rinse solution, such as sterile water.
[0050] While not intending to limit the scope of the invention, the
following examples show the effectiveness of peracetic acid-based
decontaminant solution in the destruction of bacteria, such
Listeria, and other microorganisms.
EXAMPLES
Example 1
[0051] Peracetic Acid Treatment of Pre-Cooked Frankfurters
Inoculated With Listeria monocytpgenes
[0052] Bacterial Cultures and Preparation of Inoculum
[0053] A five-strain mixture of Listeria monocytogenes was used for
purposes of inoculation. To prepare this mixture, five strains of
L. monocytogenes were grown individually in tryptic soy broth (TSB)
for 48.+-.2 h at 30.degree. C. Equivalent aliquots of broth from
each strain were then combined in a sterile test tube to achieve a
mixed inoculum containing approximately equal populations of each
of the five strains. The mixed culture was diluted as appropriate
using 0.1% peptone diluent to achieve a final mixed inoculum with a
cell density of approximately 10,000 colony forming units
(cfu)/ml.
[0054] Inoculation of Frankfurter Samples
[0055] Packages of commercially prepared beef frankfurter sausages
("franks") were obtained from a local retail outlet. TABLE 1 lists
the constituents of the franks, as provided on the packages. The
packages were stored at 4.degree. C. until use (no more than 24
hours). Immediately prior to testing, the franks were removed from
the commercial packaging and placed on a sterile surface in a
biological safety cabinet. The franks were oriented on the surface
such that no franks were in contact with each other. Using a
micropipette, each individual frank (except for those used as
controls) was inoculated with 0.1 ml of the previously prepared
mixed inoculum with a target inoculation level of 1,000 cfu/frank.
A sterile bent rod was used to spread the inoculum over the frank
surface as evenly as possible. Inoculated franks were allowed to
remain undisturbed on the sterile surface for at least 5 minutes
prior to treatment with the decontaminant solution. Three franks
were inoculated per treatment to be evaluated, one frank being
tested without inoculation.
1TABLE 1 Composition of Frankfurters Oscar Meyer Beef Franks
Ingredients: Beef, water, salt, <2% corn syrup, dextrose, flavor
beef stock, sodium phosphates, autolyzed yeast, sodium erythorbate
(made from sugar), sodium nitrite, extractives of paprika Nutrition
Facts: per 45 g link Calories 140 Cal. Fat 120 Total Fat 13 g (Sat.
6 g) Cholesterol 30 mg Sodium 460 mg Total Carbohydrate 1 g Protein
5 g
[0056] Treatment of Frankfurter with Peracetic Acid
[0057] The peracetic acid used in the evaluation was obtained as a
35% concentrate under the trade name STERIS 20.TM. Sterilant
Concentrate from STERIS Corporation (Mentor, Ohio). The concentrate
was used without the buffers or other additives supplied by the
manufacturer. The concentrate was diluted to appropriate nominal
concentrations (100, 500, and 1000 ppm). Approximately 1 L of each
concentration to be evaluated was prepared in sanitized 2 L plastic
containers. Additionally, 1 L of a control treatment, namely
sterile distilled water (0 ppm peracetic acid), was also prepared
in a 2 L container. Each of these four concentrations was evaluated
using two exposure times, 2 and 10 seconds. Therefore, a total of
eight treatments (four peracetic acid concentrations (0, 100, 500,
and 1000 ppm) at two exposure times (2 and 10 seconds) were
evaluated in this study. Each test was carried out two or more
times for establishing reproducibility.
[0058] Prior to treatment, one of the three inoculated franks per
treatment was evaluated for initial levels of L. monocytogenes
(target initial population of 1,000 cells per frank). These franks
were analyzed using the quantitative procedures outlined below.
[0059] All peracetic acid treatments were performed inside a
biological safety cabinet. Inoculated franks were dipped into the
peracetic acid treatment solution (or distilled water for the 0 ppm
samples) and allowed to remain submerged for either 2 or 10
seconds. Sterile utensils were employed to remove the franks from
the treatment solution and transfer them to a sterile distilled
water rinse. Franks were then submerged in a sterile water rinse
and remained submerged for 2 or 10 seconds (i.e., the same time as
they were exposed to the peracetic acid solution) and were removed
with sterile utensils. Immediately after removal from the sterile
water rinse, the franks were placed on a sterile surface and
allowed to air dry for 5 minutes.
[0060] For each peracetic acid concentration, three franks were
evaluated. Separate containers of sterile water rinse were employed
for each peracetic acid concentration.times.exposure time
evaluated. All three franks to be treated in a given concentration
were dipped into a common peracetic acid solution and a common
sterile water rinse.
[0061] Following air drying, one frank per treatment was placed in
a sterile Stomacher bag and analyzed quantitatively for residual L.
monocytogenes populations. The remaining two franks were retained
in sterile Stomacher bags and used for qualitative analysis, if
necessary (in the event no surviving cells were detected using
quantitative procedures).
[0062] Microbiological Analyses
[0063] To determine the number of surviving L. monocytogenes cells
(quantitative evaluation), one frank per treatment was analyzed.
The weight of the frank was determined and an appropriate volume of
0.1% peptone diluent added to achieve a 1:5 dilution. These samples
were homogenized for 2 minutes using a Stomacher Lab Blender.
Serial dilutions were prepared in 0.1% peptone diluent and
appropriate dilutions plated using spiral and/or spread plate
techniques on MOX agar. Agar plates were incubated at 30.degree. C.
for a total of 48 hours, with examination at 24 and 48 hours.
Typical L. monocytogenes colonies were counted.
[0064] Similar evaluation procedures were used for counting the
colonies for those franks treated with distilled water rather than
peracetic acid, for the untreated franks (no peracetic acid, water
or rinse treatment), and for the franks treated with water or
peracetic acid without prior inoculation.
[0065] The plating techniques used were capable of detection down
to 5 cfu/ml (1 colony/0.2 ml) for the spiral plating method and 0.5
cfu/ml for the spread plating method (1 colony/2 ml). In the event
that no surviving L. monocytogenes cells were observed using direct
plating procedures, two franks per treatment were evaluated using
qualitative (enrichment) procedures. A 10 mL aliquot of the
retained homogenate was placed added to 90 mL of UVM broth to
achieve a 1:10 dilution. These samples were shaken by hand for 1
minute and incubated at 30.degree. C. for 24 h. Following this
primary enrichment, 0.1 mL was transferred to 10 mL of Fraser broth
and incubated at 30.degree. C. for 24 h. This secondary enrichment
was then used to perform an ELISA screening procedure (TECRA
Listeria species assay). Results of this qualitative analysis were
used to indicate whether the sample was "positive" or "negative"
for the presence of Listeria species.
[0066] Differences in the observed reductions achieved with the
various concentrations of peracetic acid were compared among the
concentrations as well as compared to the reductions achieved with
the sterile water control (o ppm).
[0067] TABLE 2 lists the peracetic acid concentration, temperature,
and pH of the solutions used.
2TABLE 2 Temperature and pH of peracetic acid treatment solutions
immediately prior to use. Target PAA Actual Temperature
Concentration PAA Conc. Exposure of PAA pH at PAA (ppm) (ppm) Time
(sec) Solution (.degree. C.) Solution Replication 1 1,000 1,146 10
12.7 3.32 500 572 10 12.7 3.48 100 114 10 11.6 3.86 0 0 10 14.0
5.57 1,000 1,146 2 11.8 3.29 500 572 2 12.6 3.48 100 114 2 12.0
3.86 0 0 2 13.8 6.08 Replication 2 1,000 1,146 10 12.1 3.27 500 572
10 11.8 3.48 100 114 10 12.3 3.85 0 0 10 13.6 6.17 1,000 1,146 2
11.9 3.29 500 572 2 11.7 3.49 100 114 2 12.5 3.86 0 0 2 13.5 6.18
Replication 3 1,000 1,146 10 12.8 3.29 500 572 10 11.8 3.49 100 114
10 12.5 3.85 0 0 10 13.8 6.05 1,000 1,146 2 12.9 3.30 500 572 2
11.6 3.50 100 114 2 11.8 3.86 0 0 2 15.1 6.07
[0068] TABLE 3 shows the quantitative and qualitative
microbiological results of analysis of the Listeria-inoculated
franks. The target inoculation level before treatment was 1,000
CFU/frank. It can be seen that a 2 second treatment is sufficient
to remove most, but not all Listeria from the franks. A 10 second
treatment reduces the Listeria count below the detection limit of
the quantitative assessment procedures, although a few colonies
were detected in the qualitative procedure. The results indicate
that some samples had actual populations before treatment of
<900 CFU/frank. Because the plating scheme had a detection limit
of 900 CFU/frank, the actual populations of the samples before
treatment could not be determined in instances where the population
was <900 CFU/frank. Additionally, the plating scheme used for
samples analyzed after treatment had a detection limit of 90
CFU/frank. Therefore, the true population of any samples with a
population of <90 CFU/frank could not be specifically
determined. For any samples that had a population of <90
CFU/frank after treatment, the retained homogenate was analyzed
using qualitative (presence/absence) procedures. Positive indicates
that at least one colony grew during the test. Negative indicated
that no colonies grew.
[0069] At the 0 ppm PAA concentration, all samples after treatment
had a population of at least 90 CFU/frank, regardless of exposure
time (2 or 10 seconds). At the 100 ppm PAA concentration,
regardless of exposure time, in two of the three replications
samples had populations of at least 90 CFU/frank.
[0070] For a 10 second exposure time, samples treated in the 500
ppm PAA solution had L. monocytogenes populations less than the
detection limit of the quantitative plating procedure, however in
two of the three replications samples were found to be positive by
qualitative analysis. At the 2 second exposure time, samples
treated in the 500 ppm PAA solution had populations of <90
CFU/frank in two of the three replications, however these samples
were found to be positive by qualitative analysis.
[0071] The 1000 ppm PAA solution, regardless of exposure time,
resulted in populations of <90 CFU/frank in all three
replications. For both exposure times, two of the three ii samples
analyzed by qualitative analysis were found to be positive for the
presence of Listeria.
3TABLE 3 Quantitative and qualitative microbiological data obtained
from analysis of Listeria monocytogenes- inoculated frankfurters
before and after treatment with solutions of peracetic acid with
exposure times of 10 seconds or 2 seconds. After PAA Concentration
Treatment Estimated Actual Before Treatment (CFU/ POS/ Conc.-ppm
Conc.-ppm (CFU/frank) frank) NEG 10 sec PAA exposure followed by 10
sec deionized water rinse 0 0 Rep 1 900 90 -- Rep 2 2,700 180 --
Rep 3 <900* 90 -- 100 114 Rep 1 <900* <90* POS Rep 2 1,800
180 -- Rep 3 <900* 180 -- 500 572 Rep 1 900 <90* POS Rep 2
2,700 <90* POS Rep 3 1,800 <90* NEG 1000 1146 Rep 1 <900*
<90* NEG Rep 2 900 <90* POS Rep 3 900 <90* POS 2 sec PAA
exposure followed by 2 sec deionized water rinse 0 0 Rep 1 <900*
180 -- Rep 2 <900* 180 -- Rep 3 <900* 90 -- 100 114 Rep 1
<900* 180 -- Rep 2 900 <90* POS Rep 3 1,800 90 -- 500 572 Rep
1 900 <90* POS Rep 2 <900* <90* POS Rep 3 <900* 90 --
1000 1146 Rep 1 900 <90* NEG Rep 2 1,800 <90* POS Rep 3
<900* <90* POS *Indicates that for quantitative analysis, no
colonies were observed on the lowest dilution plated. Therefore,
the population was less than the detection limit of the plating
scheme. The detection limit for samples plated before treatment was
900 CFU/frank; the detection limit for samples plated after
treatment was 90 CFU/frank. --Indicates that the sample was not
analyzed using qualitative procedures.
[0072] The results show that it is possible to remove substantially
all Listeria from a frankfurter in ten seconds dip treatment. It
should be appreciated that the frankfurters tested were inoculated
with massive amounts of Listeria, relative to what would be
expected in practice, demonstrating the ability of peracetic acid
to decrease Listeria contamination by orders of magnitude.
[0073] Further tests using 2000 ppm sprayed over the frankfurters
for 30 seconds to one minute showed even higher kill levels, with
complete kill being achieved.
EXAMPLE 2
[0074] D-Values for Listeria monocytogenes in Peracetic Acid
Solutions
[0075] Peracetic acid solutions of 500, 1000, and 2000 mg/L (ppm)
were prepared as for Example 1, using deionized water. To 100 mL
samples of the solutions, 1.7.times.10.sup.6 Listeria monocytogenes
ATCC. 43256 per mL were added and mixed. The samples were
maintained at a preselected temperature (.degree. C..degree. C.,
.about.15.degree. C., or .about.22.degree. C.). At 10, 20, 30, 40,
and 50 seconds contact time, 1 mL was removed, neutralized, and the
Listeria monocytogenes organisms remaining were determined by
plating on TSA and incubation. Results showed that the
microorganism was destroyed in all cases, except for the sample
exposed to 500 mg/L at .about.8.degree. C. for only 10 seconds.
D-values (time required to kill one log of the test
microorganism--in this case, a reduction in microorganisms from
1.7.times.10.sup.6 initially to 1.7.times.10.sup.5) were
determined, as shown in TABLE 4. D-values below the detection limit
of the test are shown as <2 seconds.
4TABLE 4 D-values for Listeria monocytogenes Peracetic acid
concentration Temperature D-value (mg/L) Range (.degree. C.) pH
range (seconds) 500 8.3-8.5 3.7-3.7 2 500 14.7-15.0 3.4-3.6 <2
500 22.7-22.8 3.4-3.6 <2 1000 8.1-8.1 3.2-3.4 <2 1000
15.0-15.2 3.2-3.4 <2 2000 8.1-8.4 3.0-3.1 <2 2000 3.0-3.1
3.0-3.1 <2
EXAMPLE 3
[0076] Stability of Peracetic Acid Solutions
[0077] Peracetic acid solutions were prepared in deionized water as
for Example 2 to nominal concentrations of 1000 and 2000 mg/L.
Actual peracetic acid concentrations were measured at 0 and 30
minutes at around 25.degree. C. and 50.degree. C. Results shown in
TABLE 5 indicate that the solutions remained relatively stable over
the 30 minute period.
5TABLE 5 Stability of peracetic acid solutions at 25 and 50.degree.
C. over 30 minutes Concentration Concentration Temperature at 0
mins at 30 mins (.degree. C.) pH (mg/L) (mg/L) 26-29 2.7 1347 1355
50 2.7 1310 1284 26-29 2.6 2016 2017 50 2.6 1937 1959
EXAMPLE 4
[0078] Minimum Inhibitory Concentration of Acetic Acid, Lactic
Acid, Peracetic Acid, and Liquid Smoke on Generic Escherichia coli
and Salmonella spp.
[0079] The minimum inhibitory concentration (MIC) was determined
for five strains of E. coli and five strains of Salmonella spp. as
listed in TABLE 6, using acetic acid, lactic acid, peracetic acid,
and liquid smoke.
6TABLE 6 Strains of E. coli and Salmonella used in MIC Studies
Microorganism Strain E. coli ATCC. 4350 E. coli ATCC 35336 E. coli
ATCC 9546 E. coli ATCC 12043 E. coli ATCC 25922 Salmonella
enteritidis USDA-FSIS 15060 Salmonella newport ATCC 6962 Salmonella
typhimurium Dr. S. Bailey, USDA-ARS, Athens, GA Salmonellalille Dr.
L. Beuchat, University of Georgia, Griffin, GA Salmonella
montevideo Dr. L. Beuchat, University of Georgia, Griffin, GA
[0080] Each strain was subcultured on tryptic soy agar (TSA, DIFCO,
Detroit, Mich.) slants and stored at 4.degree. C. Strains were
individually transferred into 100 mL of sterile 2.times.BHI (DIFCO,
Detroit, Mich.) and incubated at 35.degree. C. for 24 hr. to reach
ca. 10.sup.9 colony forming units/mL (CFU/mL). Then, 25 mL of each
strain of E. coli was transferred into a sterile bottle (mixture
X), and 25 mL of each strain of each strain of Salmonella spp. was
transferred into a sterile bottle (mixture Y). Mixtures X and Y
were maintained separately throughout the test.
[0081] The average initial inoculum levels of E. coli and
Salmonella spp. were ca. 1.0.times.10.sup.9 CFU/mL, and ca.
8.4.times.10.sup.8 CFU/mL, respectively.
[0082] Serial dilutions were made using Butterfields' Phosphate
Buffer (BPB, Sigma, St. Louis, Mo.) in 1 mL aliquots prior to
inoculation. BPB was prepared as a stock solution by adding 34 g of
KH.sub.2PO.sub.4 to 500 mL of distilled water. The pH was adjusted
to 7.2, and the solution was brought to a volume of 1 L. The BPB
stock was autoclaved for 20 min. at 121.degree. C. and 15 lbs. of
pressure. For each of the treatments to be evaluated, (acetic acid,
lactic acid, peracetic acid, and liquid smoke) a 10 mL test tube
containing 1 mL of buffer, 1 mL of treatment, and 1 mL of mixture X
or Y was prepared. For glacial acetic acid (U.S.P.-F.C.C., J.T.
Baker, Phillipsburg, N.J.), starting concentrations and serial
dilutions were 50%, 25%, 12.5%, 6.25%, 3.12%, 1.56%, 0.78%, 0.39%,
and a control (no treatment, buffer and culture). For lactic acid,
86.30% (U.S.P.-F.C.C., J.T. Baker, Phillipsburg, N.J.), starting
concentrations and serial dilutions were 43.15%, 21.58%, 10.79%,
5.39%, 2.70%, 1.35%, 0.67%, 0.33%, and a control. For peracetic
acid 35.0% (STERIS 20.TM., STERIS Corporation, Mentor, Ohio),
starting concentrations and serial dilutions were 17.5%, 8.75%,
4.38%, 2.19%, 1.09%, 0.55%, 0.30%, 0.14%, 0.07%, 0.03%, and a
control. For liquid smoke (Hickory Specialties, Brentwood, Tenn.)
starting concentrations and serial dilutions were 50%, 25%, 12.5%,
6.25%, 3.12%, 1.56%, 0.78%, 0.39%, and a control. Dilutions were
prepared with deionized water.
[0083] The test tubes were incubated at 35.degree. C. for 24 hrs.
and turbidity was evaluated using McFarland equivalence standards,
to study the bacteriostatic properties of the diluted solutions. In
addition, each dilution was plated to evaluate the bactericidal
properties of the diluted solutions. Using a 1 .mu.L sterile loop,
each concentration and control for either microorganism mixture was
streaked on plate count agar (PCA, DIFCO, Detroit, Mich.). A
selective agar was also used for each mixture, eosine methylene
blue agar (EMB, DIFCO, Detroit, Mich.) for E. coli and xylose
lysine decarboxylase agar (XLD, DIFCO, Detroit, Mich.) for
Salmonella spp. All plates were incubated for 24 hrs. at 35.degree.
C. and were inspected for growth or no growth.
[0084] All four treatments were effective in inhibiting the growth
of generic E. coli and Salmonella spp. at different levels in
laboratory medium. A summary of the treatments, microorganisms, and
final minimum inhibitory concentration (MIC) can be found in TABLE
7. Peracetic acid inhibited the growth of E. coli and Salmonella
spp. at the lowest concentration (0.137%) of all three acids
tested.
7TABLE 7 Minimum inhibitory concentrations of liquid smoke, acetic
acid, lactic acid, and peracetic acid for E. coli and Salmonella
spp. Treatment MIC (%) Peracetic Organism Liquid Smoke Acetic Acid
Lactic acid acid E. coli 6.25 3.12 2.70 0.14 Salmonella 6.25 0.78
1.35 0.14 spp.
EXAMPLE 5
[0085] Reduction of Generic Escherichia coli and Salmonella spp. on
Pork Skin With Water, Acetic Acid, Lactic Acid, or Peracetic
Acid.
[0086] Samples of pork skin were inoculated separately with either
5 strains of E. coli or 5 strains of Salmonella spp. (mixtures X
and Y, see Example 4). Five different treatments were evaluated for
effectiveness in reducing bacteria on pork skin. The treatments
were deionized water, 2% acetic acid, 2% lactic acid, 0.1%
peracetic acid, and a control (no treatment), respectively. EMB
agar was used for E. coli and XLD for Salmonella, and a nutrient
agar was also used for E. coli and Salmonella for total count.
[0087] Bacterial Cultures
[0088] The five strains of generic E. coli and five strains of
Salmonella spp. were cultured and transferred individually into 100
mL of tryptic soy broth (TSB, DIFCO, Detroit, Mich.) with 1%
dextrose (Sigma, St. Louis, Mo.) in duplicate. Dextrose was added
to induce acid tolerance in the microbial cell. The cultures were
incubated at 35.degree. C. for 24 hrs. to obtain ca.10.sup.9 colony
forming units (CFU)/mL. The cells were harvested by the
centrifuging each culture at 10,000.times.g force for 10 min. at
4.degree. C., (Beckman J2-HS centrifuge, Beckman Instruments, Inc.,
Palo Alto, Calif.). After centrifugation, the supernatant was
poured off, and cells remained in pellet form. Each pellet was
individually re-suspended with 50 mL of 0.1% peptone water (DIFCO,
Detroit, Mich.). All five strains of E. coli or Salmonella spp.
inoculum were transferred to separate HDPE plastic spray bottles
(Sprayco.TM., Detroit, Mich.) to be used in the mist inoculation of
pork skin samples.
[0089] Media
[0090] For E. coli, PCA and EMB media were used, and for
Salmonella, PCA and XLD media were used. Bacto Plate Count Agar
(PCA) was used in this study as a standard methods medium for the
enumeration of bacteria before and after treatments. Spiral (sl) or
spread (sd) plate technique were used for viable cell counts.
Duplicate plates were performed for each treatment.
[0091] Pork Sample Preparation
[0092] Fresh pork skins taken from the loin region were cut to
rectangles of 19.35 cm.sup.2. A hole was bored into the top of each
sample so that each sample could be suspended from an individual
hook in the spray cabinet. Samples were laid out onto trays wrapped
in butcher paper. Each tray was individually spray inoculated with
E. coli or Salmonella spp. in a Plexiglas spray chamber to ca.8.4
mL of inoculum. After the inoculation, each tray was placed under a
laminar flow hood for 1 hr. to allow the surface to dry and for the
attachment of the bacteria to the pork skin.
[0093] The peracetic acid (PAA) used in this study was a 35.0% PAA
buffered, liquid solution prepared from a STERIS 20.TM. two
compartment cup (a dry powder containing anticorrosive additives,
buffers, sequestrants, and surfactants). The peracetic acid
determined before each use of the treatment using a calibration
curve.
[0094] Treatment Application
[0095] Five inoculated samples were individually placed on
stainless steel hooks in a spray cabinet at ambient
temperature.
[0096] The samples were exposed to a continuous spray of the
selected treatment for 5 seconds at a spray pressure of 16-18
psi.
[0097] The treated samples were placed into individual stomacher
bags containing 30 mL of 0.16 peptone water (DIFCO, Detroit, Mich.)
and stomached for 2 min. Serial dilutions of 0, 10.sup.-2, and
10.sup.-4 were spiral plated (WASP spiral plater, Bioscience
International, Rockville, Md.) on PCA (DIFCO, Detroit, Mich.) and
EMB (DIFCO, Detroit, Mich.) for E. coli and on plate count agar
(PCA, DIFCO, Detroit, Mich.) and xylose lysine decarboxylase agar
(XLD, DIFCO, Detroit, Mich.) for Salmonella spp. Samples were also
spread plated on PCA and EMB agar for E. coli or PCA and XLD agar
for Salmonella spp, using 0.25 .mu.L/plate for a total of 1 mL on 4
plates. This was to ensure a countable plate. Plates were inverted
and incubated at 35.degree. C. for 24 hrs. (48 hrs. for Salmonella
spp.).
[0098] Titratable Acidity And pH
[0099] Titratable acidity (TABLE 8) was determined according to
AOAC methods (JAOAC 30, 130: 1947;34,239: 1951), sing a {fraction
(1/10)} dilution factor. Phenylethylene was used as the indicator
with 0.1N NaOH as the base. The pH of acetic and lactic acid was
determined during each replication using a standardized pH meter
(Orion Research, Inc., Beverly, Mass.).
8TABLE 8 Average titratable acidity and pH values for acetic and
lactic acid used on Escherichia coli and Salmonella spp. Treatment
Microorganism Titratable Acidity (mL) pH Acetic acid E. coli 2.65
2.54 Acetic acid Salmonella spp. 2.45 2.55 Lactic acid E. coli 2.07
2.10 Lactic acid Salmonella spp. 1.93 2.08
[0100] Microorganism Count
[0101] Microorganism counts on the different agar plates are
provided in TABLE 9.
9TABLE 9 Log CFU/cm.sup.2 of Eschericia Coli and Salmonella spp. on
inoculated pork skins after 24 hours (E. coli)/ 48 hours
(Salmonella) Total Count Total Count Total Count Total Count (E.
coli) on (E. coli) on (Salmonella) (Salmonella) Treatment PCA EMB
on PCA on XLD No treatment 6.55 6.54 6.46 5.72 Water 5.25 5.15 6.05
5.78 2% Lactic acid 3.96 4.02 4.95 2.97 0.1% Peracetic 3.28 3.04
5.34 3.83 Acid 2% Acetic 4.68 4.55 5.37 4.27 Acid
[0102] Peracetic acid (0.1%) (PAA) can be seen to be an effective
rinsing agent for Salmonella and E. coli, even though used at much
lower concentration than the lactic acid or acetic acid. Acetic
acid, lactic acid, and peracetic acid were all found to be
effective in inhibiting the growth of E. coli and Salmonella spp.
at lower concentrations than for liquid smoke. As seen from TABLE
7, the minimum inhibitory concentration (MIC) using the test tube
dilution method indicated that the most effective antimicrobial for
generic E. coli and Salmonella spp. was peracetic acid. Liquid
smoke had the highest MIC of 6.25% for E. coli and Salmonella spp.
compared to the organic acids.
[0103] Peracetic acid (0.1%) was the most effective treatment on
pork skin for E. coli, achieving 3 log/cm.sup.2 reduction and was
significantly (p.ltoreq.0.05) different from all other treatments.
Lactic acid (2%) was the most effective treatment for Salmonella
spp., achieving almost 3 log/cm.sup.2 reduction. After 24 hrs.
Salmonella spp. showed little to no recovery; therefore, an
additional 24 hrs. incubation period was evaluated. This suggested
that the Salmonella spp. were more susceptible to acid injury
compared to E. coli cells.
[0104] The selective agars used suggested higher reductions than
the nutrient agar.
[0105] The studies suggest that decontamination rinses are
effective in reducing the amount of bacteria in laboratory media
and on pork skin.
[0106] Statistical Analysis
[0107] Bacterial enumeration data from the three replications of E.
coli and Salmonella spp. were analyzed by the analysis of variance
using the General Linear Model procedure of Statistical Analysis
System (SAS Institute, Inc., 1990). LSD was used to separate the
means of the log CFU/cm.sup.2 samples.
[0108] For generic E. coli, all treatments were significantly
different (ps0.05) on both PCA and EMB. For Salmonella spp. on PCA,
there were no significant differences (>0.05) between the
samples that were treated with water (W) and the samples that were
untreated (NT). Acetic acid (AC) showed no significant difference
(p>0.05) from lactic acid (LA), or peracetic acid (PAA),
indicating that the organic acids were reducing Salmonella spp. to
approximately the same level. For Salmonella spp. on XLD, there
were significant differences (p.ltoreq.0.05) between the untreated
samples (NT) and the samples treated with water (W). Acetic acid
(AC) and peracetic acid (PAA) were not significantly different
(p>0.05). The lactic acid (LA) treatment was significantly
different (p.ltoreq.0.05) from all other treatments.
[0109] The invention has been described with reference to the
preferred embodiment. Obviously, modifications and alterations will
occur to others upon reading and understanding the preceding
detailed description. It is intended that the invention be
construed as including all such modifications and alterations
insofar as they come within the scope of the appended claims or the
equivalents thereof.
* * * * *