Method for preserving food products

A method for preserving a food product, such as meat, is provided. The method comprises the steps of inoculating meat with an effective amount of euhygienic non-pathogenic, non-spoilage bacteria in order to competitively inhibit the growth of undesired pathogenic and spoilage bacteria. Preferably, either L. delbrueckii or Hafnia alvei bacteria are used to inoculate a meat product. Bacteria present on a meat product is first reduced to a number below about 5000 bacteria per gram of meat, e.g. by dehairing an animal and then spraying the meat with an organic acid prior to inoculation with euhygienic bacteria. The meat product is then vacuum packaged and stored in a refrigerated environment of about -1.degree. C. to about 7.degree. C. Meat products preserved in accordance with the method of the invention can enjoy a refrigerated shelf life of up to about 150 days without surface discoloration or the generation of undesirable gaseous by-products.

FIELD OF THE INVENTION 
This invention relates to a method for preserving food products, and 
particularly meat and meat by-products and food products produced thereby. 
More particularly this invention relates to a method for preparing a meat 
product having a shelf life of up to 150 days by dehairing an animal, 
removal of the hide of the animal, contacting the animal carcass with weak 
organic acids, and inoculating meat with euhygienic bacteria to 
competitively inhibit and/or exclude the growth of undesired pathogenic 
and spoilage bacteria. 
BACKGROUND OF THE INVENTION 
In the meat industry, and particularly in those areas devoted to the 
processing of beef and pork, meat packers slaughter animals in a process 
in which the animals are stunned, bled, skinned, eviscerated, and 
fabricated into meat sections which are then marketed in grocery stores 
and in the restaurant trade. Animals enter a meat slaughter plant with 
various foreign materials present on their hair, including blood, dirt, 
manure, mud, and vegetative material. An animal's hair is also 
contaminated with a multitude of microorganisms, some of which are 
pathogenic to humans. Most bacteria present in a meat slaughtering and 
processing facility are carried into the facility on the hides of animals 
to be slaughtered. During the slaughtering process these microorganisms 
contact meat and other meat by-products, thereby contaminating such 
products, creating handling problems and reducing the shelf life and 
safety of the meat products. 
The control of contamination by microorganisms is a recognized problem in 
the meat packing industry. The preparation of food products, and 
particularly fresh meat and meat products for the retail market, is 
largely concerned with the control of microbial contact with food in order 
to increase the shelf life of food products. Food products having an 
extended shelf life afford more time in which handlers, shippers, and 
wholesalers can transport and sell such food before spoilage occurs. 
Efforts to increase the shelf life of food products, such as meat, have 
traditionally been focused on reducing the number of bacteria present on 
the surface of the food product. 
Freezing food, and particularly meat, has proven to be an effective way in 
which to retard the growth of bacteria that may be present on the surface 
of the food. The freezing of meat, however, especially for extended 
periods of time, has many undesirable effects. By freezing a meat product, 
water within the meat crystallizes, causing the denaturing of proteins and 
other damage to the meat on a cellular level. Moreover, the texture, 
consistency and taste of thawed frozen meat is less desirable than that of 
fresh meat. Because of the relative short shelf life of fresh meat, 
foreign markets can only be reached by freezing domestic meat products. 
Many foreign meat consumers, such as those in the Pacific rim countries 
and Europe, prefer fresh meat to frozen meat. Such fresh meat preference 
effectively preclude foreign sales of domestic meat. Without freezing the 
meat product, however, the bacteria that has contacted the meat during 
processing are able to proliferate, creating spoilage and pathogenic 
concerns. 
The opportunity for bacterial contact with the fresh meat begins when an 
animal is initially presented for processing and extends up until the time 
the meat product is consumed. The initial bacterial contact with fresh 
meat is encountered with a meat processing facility due to the 
contaminated state of the animal when it enters the facility. Further 
opportunities for bacterial contact arise from the significant amount of 
human handling and equipment exposure during the slaughter, processing, 
and transportation of meat products. Moreover, when consumers remove the 
wrapping of a meat product for cooking, additional opportunities present 
themselves for bacterial infection. 
The time between the initial opportunity for bacterial contact with meat 
products and the ultimate consumption of such products by consumers, 
allows for the proliferation of various forms of bacteria, including the 
growth of undesired spoilage and pathogenic bacteria. The growth of 
undesired bacteria on meat presents aesthetic concerns affecting the 
marketability of meat products. For example, growth of spoilage bacteria 
creates undesired odors due to bacterial production of certain esters, 
hydrogen sulfide, nitrogenous compounds, ruturic acid, propionic acid, 
formic acid, as well as other undesirable gases and acids. The growth of 
other such bacteria also acts to discolor the surface of the meat. 
Moreover, when meat packaged in permeable plastic packages spoils, the 
packaging often inflates due to the generation of gas produced by spoilage 
bacteria. 
Contamination of meat with pathogenic bacteria is also a great concern 
since such bacteria, or toxins produced by such bacteria, can cause 
illness or disease in humans and animals who consume such meat. The shelf 
life of a meat product is directly related to the number of spoilage and 
pathogenic bacteria present on the surface of the meat product. A meat 
product having a high level of spoilage and pathogenic bacteria on its 
surface exhibits a relatively short shelf life, whereas meat having a low 
count of spoilage and pathogenic bacteria exhibit an extended shelf life. 
There has been a long felt need in the meat packaging industry for 
controlling undesired bacterial proliferation in order to avoid spoilage 
and thereby increase the shelf life of meat products. Government standards 
also mandate that meat processing facilities attain certain tolerances 
which have been set regarding the number of potentially hazardous bacteria 
that meat may contain. Methods by which undesired bacterial growth on meat 
can be controlled are therefore desired. 
In a meat processing facility, animals are slaughtered and fabricated in a 
process which progressively disassembles the animal to produce meat cuts 
for sale to customers. When an animal to be slaughtered enters a 
processing facility, it typically has a great variety of bacteria present 
on its hide. Bacteria present on an animal primarily originate from the 
foreign material present on an animal's hide, including blood, dirt, 
manure, mud and vegetative material. The necessary handling of meat 
products during the fabrication process provides additional opportunities 
for meat to come into contact with bacteria. In conventional meat 
processing facilities, it has not been economically feasible to remove all 
sources of material contact with the meat or to maintain perfect 
environmental conditions to retard bacterial growth. 
The prior art utilizes several methods to prolong the retail acceptability 
of meat products. For example, vacuum packing of meat in gas permeable 
packages is commonplace. Irradiation with ultraviolet light has been used 
to reduce the number of microorganisms on meat surfaces. Salting of meat 
has long been practiced to preserve meat products. Refrigeration is also 
widely used to deter the rapid growth of spoilage and pathogenic bacteria 
on meat products. Spoilage bacteria, such as pseudomonas, are known to 
grow most rapidly at about room temperature. Although such bacteria are 
present on meat at lower temperatures, their growth is significantly 
slowed by cooler environments. Mere refrigeration alone, however, is not 
totally effective in preventing or adequately retarding the growth of 
spoilage or pathogenic bacteria for any appreciable amount of time. 
The shelf life of meat has also been extended somewhat by the use of 
chemical agents. Chemical treatment of meat to destroy surface bacteria 
has traditionally been accomplished by treating meat with weak acids 
and/or chlorine solutions. These conventional techniques, however, often 
create undesirable color, flavor and order modifications of meat, and are 
often ineffective to maintain meat in a saleable condition for any 
appreciable period of time. 
Although the control of spoilage and pathogenic bacterial growth is a 
recognized problem in the meat packing industry, the reduction of meat 
shelf life attendant to such growth continues to be a significant problem. 
Many techniques have been employed in the past in an effort to destroy 
surface bacterial flora on meat. For example, U.S. Pat. No. 4,852,216 to 
Clayton discloses a disinfection system using an acetic acid spray in 
order to reduce bacterial levels and thereby increase shelf life of meat 
products. Similarly, U.S. Pat. No. 3,924,044 to Busch discloses a method 
for applying a hot, dilute acid solution to meat surfaces to destroy 
psychotropic spoilage bacteria on meat surfaces. U.S. Pat. No. 3,991,218 
teaches the encapsulation of meat products in a film of alginate material 
to retard the growth of anaerobic bacteria on the surface of the meat. 
Other inventors have utilized anti-microbial agents for preserving 
products normally subject to microbial spoilage. For example, U.S. Pat. 
No. 3,915,889 to Jurd discloses a certain anti-microbial agent that can be 
applied for preservation for a wide variety of substances including meat. 
Other inventors have recognized the advantages of dehairing animals to 
facilitate the slaughtering process. U.S. Pat. No. 4,674,152 to Georges 
discloses an apparatus and method for slaughtering animals by bleeding an 
animal, electrostatically charging the animal's hair, applying a 
combustible fluid to the hair and subsequently igniting the combustible 
fluid to burn the hair from the animal's body. U.S. Pat. No. 4,309,795 to 
Simonsen discloses a method and apparatus for de-hairing hogs wherein the 
hog is bled, its skin is scalded with hot water, and then subjected to 
abrasive treatment to remove the hogs hair. 
In a direct teaching away from the present invention, other researchers 
have concluded that contacting meat products with lactic acid bacteria, 
and thereafter vacuum packaging such meat in impermeable plastic, is 
ineffective in controlling the growth of pathogenic and spoilage bacteria 
on the meat. For example, the companion articles by Hanna et al., 
"Inoculation of Beef Steaks with Lactobacillus Before Vacuum Packaging, I. 
Microbiological Considerations," Journal of Food Protection, Vol. 43, pp. 
837-841 (November 1980) and Smith, G. C. et al., "Inoculation of Beef 
Steaks with Lactobacillus Species Before Vacuum Packaging. II. Effect on 
Meat Quality Characteristics," Journal of Food Protection, Vol. 43, pp. 
842-849 (November 1980) disclose that disadvantages outweigh advantages 
for inoculation of beef with Lactobacillus cultures prior to vacuum 
packaging of meat. In addition, Egan et al., "Significance of Lactobacilli 
and Film Permeability in the Spoilage of Vacuum-Packaged beef," Journal of 
Food Science, Vol. 47, pp. 119-126 (1982) disclose that even in the 
absence of a significant population of contaminating microorganisms, 
sterile vacuum packaged beef has a limited shelf life and the addition of 
Lactobacillus bacteria to vacuum packaged meat increases the rate of 
spoilage. Therefore, no prior art techniques have taught the effective 
elimination of growth of undesired bacteria to achieve a significant 
extension of shelf life in fresh meat products. 
In the meat packing industry, many types of bacteria are known to cause 
food poisoning including: E. coli, Salmonella, F. coliforms, Listeria, 
Staphylococcus, F. streptococcus, Bacillus anthraces, Balantidium coli, 
Campylobacter coli, Campylobacter jejune, Francisella tularensis, 
Sarcocystis, Taenia saginata, Taenia solium, Toxoplasma gondil, 
Trichinella spiralis, Yersinia enterocolinea, Yersinia pseudotuberculosis, 
Brucella, Chlamydia petechia, Leptospira and Clostridium. These pathogenic 
bacteria each group and proliferate under different conditions, any or all 
of which may be present in a meat processing facility. For example, 
Listeria is generally found in cool, damp environments such as coolers and 
meat processing areas. Staphylococcus is often found on cattle hair, in 
fecal material, in infected cuts and internal abscesses, and is sometimes 
associated with poor hygienic practices of food handlers. 
Spoilage bacteria, including psychotropic bacteria such as Pseudomonades, 
Lactobacillus and Coliform, affect the shelf life of meat products by 
causing discoloration of meat and undesired odors. These bacteria are 
typically found in soil, ingesta, and fecal material that are commonplace 
on an animal's hide. 
The bacteria present on an animal's hide can be roughly divided into three 
distinct categories: pathogenic bacteria, lactic bacteria, and spoilage 
bacteria. In the environment of a meat processing facility, spoilage 
bacteria typically proliferate at a greater rate than do pathogenic 
bacteria or lactic bacteria. It has been recognized that various 
sanitizing techniques, including acetic acid sprays, application of 
anti-microbial agents, and irradiation, can be used to reduce the total 
number of bacteria present on an animal carcass. However, while the total 
number of bacteria can be reduced, it is difficult to specifically kill 
pathogenic and spoilage bacteria without eliminating all the bacteria 
present on an animal carcass. 
Additional difficulties are experienced in the control of certain types of 
bacteria, namely Salmonella and Listeria, which initially infect meat by 
implanting themselves on meat surfaces. After contact, such bacteria 
immediately initiate the secretion of a waxy material to protect 
themselves from the outside environment. Unless these bacteria are 
contacted with chemical agents, such as acetic acid, before significant 
implantation and secretion of waxy substances, such bacteria are extremely 
difficult to remove from the meat. 
Conventional wisdom in the meat processing industry teaches the maintenance 
of low bacterial counts as measured by the total number of bacteria on a 
meat product. For example, if bacterial counts exceed about ten million 
bacteria per gram of meat, the meat is disposed of as a matter of course. 
However, a total bacterial count includes not only the number of 
pathogenic and spoilage bacteria, but also non-pathogenic, non-spoilage 
bacteria. 
In view of the above, a need exists for a method for preserving food 
products, particularly fresh meat and meat by-products, by selectively 
reducing the number of spoilage and pathogenic bacteria present on such 
food products. 
SUMMARY OF THE INVENTION 
The present invention includes a method for preserving food products, such 
as meat, by inoculating such food products with an effective amount of 
euhygienic bacteria. Euhygienic bacteria are non-pathogenic and/or 
non-spoilage bacteria able to competitively inhibit and/or exclude the 
growth of pathogenic and spoilage bacteria. The euhygienic bacteria used 
in the present invention create essentially no malodors or discoloration 
of food products, such as meat, and thus act to extend the shelf life of 
foods products. The present invention specifically is applicable to the 
preservation of meat from poultry, beef, pork, lamb, fish and seafood, as 
well as to dairy products, vegetables, fruits and grains. 
In one embodiment of the invention, euhygienic bacteria are preferably 
facultative, sacrophilic, gram positive bacteria, and more preferably 
bacteria of the genus Lactobacillus. Euhygienic bacteria are preferably 
obligately homofermative lactobacilli but can also be facultatively 
heterofermentive lactobacilli. 
In another embodiment of the invention, euhygienic bacteria include 
Lactobacillus delbrueckii, L. leichmannii, L. jensenii, L. lactis, L. 
bulbaricus, L. helveticus or L. acidophilus. In a preferred embodiment of 
the invention the euhygienic bacteria are predominately of the species L. 
delbrueckii or Hafnia alvei, or a combination of L. delbrueckii and Hafnia 
alvei. 
In accordance with one embodiment of the present invention, a food product 
is inoculated with euhygienic bacteria able to proliferate at temperatures 
from about -1 C. to about 35.degree. C. Another embodiment involves 
reducing the number of bacteria present on a food product, preferably 
below about 5000 bacteria per gram of food product, prior to inoculation 
with an effective amount of euhygienic bacteria. Inoculation of a food 
product is performed prior to packaging of the food product, preferably 
with impermeable plastic wrapping. In one embodiment of the present 
invention freeze dried euhygienic bacteria are placed inside a food 
package prior to sealing of the package. Reduction of the number of 
bacteria on a food product may be accomplished in various ways including 
irradiating the food, exposing the food to elevated temperatures, 
contacting the food with antibiotics, or contacting the food with an 
organic acid such as lactic or acetic acid. 
In yet another embodiment of the invention, the surface of a food product 
is inoculated with Hafnia alvei bacteria. Hafnia alvei bacteria are 
believed to initially colonize the meat surface and create an environment 
conducive to the growth of L. delbrueckii bacteria. The subsequent or 
coincidental inoculation of the meat with L. delbrueckii competitively 
inhibits and/or excludes the growth of undesired pathogenic and spoilage 
bacteria. 
The present invention also includes the adjustment of the pH on the surface 
of meat to create an environment conducive to the growth of euhygienic 
bacteria. In one embodiment of the invention, meat is contacted with 
lactic or acetic acid to establish a meat surface pH of about 4 to about 
7, and more preferably to between about 4 and 5, permitting the selective 
growth of euhygienic bacteria, such as L. delbrueckii or Hafnia alvei, 
over the growth of pathogenic and spoilage bacteria. 
In another embodiment, an animal carcass, or meat therefrom, is inoculated 
with euhygienic bacteria after application to the carcass of an organic 
acid, such as acetic or lactic acid, and prior to the vacuum packaging of 
the meat in oxygen impermeable wrapping. 
A further embodiment of the method includes maintaining an animal carcass 
or meat therefrom at a temperature of about -1.degree. C. to about 
7.degree. C. after inoculation with an euhygienic bacteria. In alternative 
embodiments, the total number of bacteria present on an animal carcass is 
reduced and the animal carcass is inoculated with an effective amount of 
euhygienic bacteria able to produce antibiotics toxic to pathogenic and 
spoilage bacteria. 
The present invention also includes food products prepared in accordance 
with the above mentioned method. Specifically, in one embodiment of the 
invention a meat product is produced having a shelf life of over about 40 
days and up to about 150 days with its surface primarily populated with 
euhygienic bacteria. 
Other embodiments of the invention are directed to the reduction of 
malodors, and/or discolorations of food products, the inhibition of 
undesired bacterial growth on food products, and the tenderizing of meat 
products by inoculating food or meat products with an effective amount of 
euhygienic bacteria. Another embodiment of the invention includes the 
effective reduction of the growth of spoilage and pathogenic bacteria 
within a food processing facility by inoculating the food processing 
facility and/or equipment therein, with an effective amount of euhygienic 
bacteria.

DETAILED DESCRIPTION OF THE INVENTION 
In the preparation of a food product, and particularly a meat product, for 
animal or human consumption, one of the paramount concerns is to reduce 
the number of bacteria present on the surface of the food product. The 
reason bacterial control on a food product is so important is that certain 
types of bacteria, namely pathogenic and spoilage bacteria, shorten the 
shelf life of food products by multiplying on food surfaces, thereby 
generating undesired by-products that cause malodors, discoloration or 
poisoning of the food. 
The term "food product" as used herein refers to any food that is 
susceptible to spoilage as a result of bacterial growth and proliferation 
on the surface of the food. Such food products include, but are not 
limited to meat, vegetables, fruits and grains. 
As used herein, the term "meat" refers to any fresh meat product or meat 
by-product from an animal of the kingdom Animalia which is consumed by 
humans or animals, including without limitation meat from bovine, ovine, 
porcine, poultry, fish and crustaceous seafood. Thus, while one of the 
primary uses for the present invention relates to meat processed in the 
slaughtering of mammals in a meat processing facility, it is to be 
expressly understood that the invention has application in the processing 
of other edible meat products including fish, poultry and seafood. 
Moreover, it is contemplated that the method also will have use in 
connection with the preservation of non-animal food products, such as 
fruits, vegetables and grains, subject to spoilage by bacterial 
microorganisms. 
As used herein the term "shelf life" means the period of time that a food 
product remains saleable to retail customers. In traditional meat 
processing, the shelf life of fresh meat and meat by-products is about 30 
to 40 days after an animal has been slaughtered. Refrigeration of meat 
during this period of time largely arrests and/or retards the growth of 
pathogenic bacteria, and to a lesser extent, spoilage bacteria. After 
about 30 to 40 days, however, refrigeration is no longer able to 
effectively control the proliferation of spoilage bacteria below 
acceptable levels. Spoilage bacteria present on meat products after this 
time period are able to assimilate proteins and sugars on meat surfaces 
and begin to generate undesired by-products. Spoilage bacteria may also 
act to discolor meat, making such meat unappealing and undesirable for 
human consumption. 
The term "spoilage bacteria" as used herein refers to any type of bacteria 
that acts to spoil food. Spoilage bacteria may grow and proliferate to 
such a degree that a food product is made unsuitable or undesirable for 
human or animal consumption. Bacteria are able to proliferate on food 
surfaces, such as meat surfaces, by assimilating sugars and proteins on 
such surfaces. By metabolizing these components, spoilage bacteria create 
by-products including carbon dioxide, methane, nitrogenous compounds, 
butyric acid, propionic acid, lactic acid, formic acid, sulfur compounds, 
and other undesired gases and acids. The production of such by-products 
alters the color of meat surfaces, often turning meat from a red color to 
a brown, grey or green color. Gaseous by-products generated by spoilage 
bacteria also give spoiled meat an undesirable odor. The color and odor 
alterations of meat due to the growth of spoilage bacteria on a meat 
product's surface often makes such meat unsalable to consumers. 
In addition to the control of spoilage bacteria, another significant 
concern in the food processing industry is controlling the growth of 
pathogenic bacteria. As used herein, the term "pathogenic bacteria" refers 
to any food poisoning organism that is capable of causing disease or 
illness in animals or humans. The term pathogenic bacteria will be 
understood to include bacteria that infect meat and thereby cause disease 
or illness, as well as bacteria that produce toxins that cause disease or 
illness. The proliferation of pathogenic bacteria on food products can 
cause severe illness and may be deadly, as demonstrated by the number of 
human fatalities caused by botulism. The term "undesired bacteria" as used 
herein, refers to both spoilage and pathogenic bacteria. For purposes of 
illustration only and without being limited thereby, the term "undesired 
bacteria" includes obligately heterofermentative Lactobacilli. Such 
bacteria ferment hexoses to lactic acid, acetic acid, ethanol and CO.sub.2 
and are also known to ferment pentoses to lactic acid and acetic acid. 
Pathogenic and spoilage bacteria can be aerobic, anaerobic or facultative, 
and thus, the elimination of oxygen alone from a food package or from a 
food storage environment will not effectively eliminate all types of 
undesired bacteria. Moreover, control of the temperature in the storage of 
food is not totally effective to preclude the growth of such bacteria 
because several types of pathogenic and spoilage bacteria are able to grow 
at various temperatures. While exposure to very high temperatures is known 
to be effective in killing most bacteria, such exposure may damage at 
least a portion of a food product by essentially cooking the food. High 
temperatures may also act to denature enzymes necessary for desired aging 
of meat products. Moreover, certain pathogenic bacteria produce toxins 
that are not destroyed by exposure to elevated temperatures. Thus, raising 
the temperature of food is not a practical way in which to effectively 
eliminate the negative effects of pathogenic bacterial contamination of a 
food product. 
Conventional practice in the meat processing industry teaches that the less 
bacteria present on a meat product, the safer such meat product will be 
for human consumption. Attempts have thus been made to essentially 
sterilize the surface of meat to control bacterial growth thereon. As used 
herein, the term "sterilize" refers to the significant reduction of the 
number of bacteria from the surface of a food product. In a more specific 
sense, the term means effectively de-populating a food product's surface 
of bacteria. In one embodiment of the invention, the number of undesired 
bacteria on a food product is reduced to below about 5000 bacteria per 
gram of food product. Conventional methods for sterilizing food products, 
such as meat, include contacting meat with weak organic acids, applying 
anti-biotic substances to meat, exposing meat to high temperatures and 
irradiating meat with high frequency radiation or x-rays. These and other 
methods can be used in conjunction with the present invention to 
substantially reduce the number of bacteria present on meat products. Such 
other methods include de-hairing of an animal prior to dispatching of the 
animal to remove microorganisms associated with the animal's hair. One 
preferred method of de-hairing an animal, and thereby vastly reducing the 
number of bacteria on the animal's hide, is to contact a depilatory 
substance to an immobilized animal and subsequently to remove its hair 
prior to the slaughtering of the animal. 
While effective in reducing the number and kinds of bacteria on food 
products such as meat, the above-mentioned methods are not able to 
continuously control the growth of spoilage and pathogenic bacteria. For 
example, by sterilizing an animal carcass, post-sterilization bacterial 
contact of the animal carcass by indigenous bacteria, including pathogenic 
and spoilage bacteria, is still possible. When a meat product is 
essentially rid of all forms of bacteria, pathogenic and spoilage bacteria 
present in the ambient environment have a new opportunity to colonize the 
animal carcass. Thus, once an animal carcass has been sterilized, it has 
traditionally been of utmost importance to maintain a sterile environment 
to preclude the opportunity for additional contact of the meat by 
undesired bacteria. 
Maintenance of an essentially sterile environment within a meat packing 
facility, however, is practically impossible using current technology. As 
such, a method is needed that can preclude the growth of pathogenic and 
spoilage bacteria subsequent to the effective sterilization of an animal 
carcass. The present invention fulfills this need by inoculating meat of 
an animal with a desired euhygienic, non-pathogenic, non-spoilage 
bacteria, immediately after the animal has been de-haired, had its hide 
removed, and sterilized. In such a manner, euhygienic bacteria are able to 
colonize the animal carcass and thereby competitively inhibit and/or 
exclude the growth of undesired pathogenic and spoilage bacteria. 
As used herein, the term "euhygienic bacteria" generally refers to a 
hygienic control bacteria that does not generate a significant or 
unacceptable amount of undesired by-products during its growth and 
proliferation. The term "euhygienic bacteria" is therefore understood to 
include non-spoilage bacteria as well as non-pathogenic bacteria. The term 
also includes any bacteria that may be genetically altered to delete or 
otherwise ameliorate qualities that would effect the salability and/or 
edibility of a food product, including without limitation bacteria altered 
to reduce production of carbon dioxide, methane, nitrogenous compounds, 
sulfur compounds, propionic acid, butyric acid, formic acid, as well as 
other undesirable compounds. 
Euhygienic bacteria are preferably obligately homofermentative lactobacilli 
that ferment hexoses almost exclusively to lactic acid by the 
Embeden-Meyerhof pathway. A preferred embodiment of euhygienic bacteria do 
not ferment gluconate or penroses. 
Another type of euhygienic bacteria is classified as a facultatively 
heterofermentative lactobacilli. This class of euhygienic bacteria ferment 
hexoses almost exclusively to lactic acid by the Embeden-Meyerhof pathway. 
In addition, some species of euhygienic bacterial ferment hexoses to 
lactic acid, acetic acid, ethanol and formic acid under glucose 
limitation, and are known to ferment pentose to lactic acid and acetic 
acid via an inducible phosphoketolase. In one embodiment of the present 
invention, euhygienic bacteria are facultative, sacrophilic gram positive 
bacteria that do produce minimal undesirable by-products during growth and 
proliferation. 
The term "inoculation" as used herein, refers to any method for effectively 
contacting bacteria to a surface so that such bacteria can proliferate on 
such surface. The surface of food products such as meat, as well as 
surfaces of food processing equipment, may be inoculated in any manner 
which effectively contacts desired bacteria to such surfaces. Such 
inoculation methods may include, but are not limited to, spraying a 
surface, such as an animal carcass, with effective amounts of, or 
immersing an animal carcass in, a solution containing desired euhygienic 
bacteria. Inoculation of meat can also be performed by placing an 
effective quantity of freeze dried euhygienic bacteria into a plastic bag 
with a meat product. The bag can then be evacuated of air and the moisture 
from the meat can then re-hydrate the freeze-dried bacteria, thereby 
allowing bacterial colonization of the meat. The general goal common to 
all inoculation methods is to contact a surface with a sufficient quantity 
of euhygienic bacteria to colonize that surface and thereby inhibit and/or 
exclude the growth of undesired bacteria thereon. Inoculation of ground 
food products, such as ground beef, may be accomplished by contacting the 
food product with euhygienic bacteria before, after, or during the 
grinding of the food products. 
Euhygienic bacterial solutions can be prepared in acceptable amounts and 
under appropriate environmental conditions, such preparation dependent 
upon various factors, such as the specific type of euhygienic bacteria 
used, the food product to be inoculated and the type of undesired bacteria 
to be inhibited and/or excluded. For example, an effective solution for 
inoculating meat with the euhygienic bacteria L. delbrueckii may be 
prepared by growing a culture of the euhygienic bacteria in a flask at a 
suitable temperature, e.g. about 35.degree. C. for approximately 24 hours. 
The solution can then be diluted with suitable medium and applied to the 
meat. Dilution of euhygienic bacterial solutions prior to application is 
also dependent upon the factors listed above, with the general goal being 
the effective inoculation of a food product with euhygienic bacteria able 
to competitively inhibit the growth of undesired bacteria. In one 
embodiment, for example, an euhygienic bacterial solution is diluted to 
approximately one part of bacterial broth grown in the above-described 
manner for every ten parts of additional media. 
Preferably, euhygienic bacteria are applied to a food product during the 
logarithmic growth phase of such bacteria. Therefore, euhygienic bacterial 
solutions should be formulated so that there is an ample food source 
available to support continued euhygienic bacterial growth and 
proliferation. A preferred food source media or broth for euhygienic 
bacteria comprises a mixture of simple and complex carbohydrates including 
but not limited to glycerol, ribose, galactose, D-glucose, D-fructose, 
D-mannose, N-acetyl-glucosamine, amygdalin, esculin, salicin, cellobiose, 
maltose, trehalose, and beta gentiobiose. In a preferred embodiment, the 
euhygienic bacterial growth broth is maintained at a temperature of 
between 5.degree. C. and 35.degree. C. The resulting euhygienic bacterial 
broth preferably has a pH of between about pH 4.1 and about pH 4.6. 
As used herein, the term "competitive inhibition" means the inhibition of 
growth of undesired bacteria by creating an environment where euhygienic 
bacteria can competitively assimilate sugars and proteins present on a 
meat surface and thus, proliferate to effectively exclude the growth of 
undesired bacteria. The term "inhibition" as used herein, means the 
killing of a microorganism, such as an undesired bacteria, or the control 
of the growth of a microorganism. As used herein, the term "exclusion" 
means the crowding out of one microorganism by another. The terms 
"inhibition" and "exclusion" are collectively used herein to mean the 
mechanism by which the growth of undesired bacteria is controlled to allow 
for the growth and proliferation of euhygienic bacteria. 
Under one theory of how competitive inhibition operates, one type of 
bacteria is able to competitively inhibit the growth of other forms of 
bacteria by effectively proliferating to such an extent that other forms 
of bacteria are unable to contact the food surface. Because the growth of 
bacteria requires access to the surface of food in order to assimilate 
sugars and proteins thereon, bacteria first able to multiply and occupy 
the surface of a food product can effectively preclude the growth of other 
forms of bacteria. Thus, to be effective in the present invention, 
euhygienic bacteria must be able to grow and multiply fast enough to 
substantially colonize a food surface before undesired bacteria are able 
to significantly proliferate on the same surface. By using the present 
method, euhygienic bacteria are allowed to multiply, crowd out, and 
thereby exclude the growth of undesired bacteria, thereby preventing the 
spoilage and pathogenic infection of food. 
In accordance with one embodiment of the present invention, meat is 
inoculated with an effective amount of euhygienic bacteria able to 
competitively inhibit and/or exclude the growth of pathogenic and spoilage 
bacteria. In this embodiment, the euhygienic bacteria used a facultative, 
sacrophilic, mesophilic gram positive bacteria. More particularly, the 
present invention includes the use of euhygienic bacteria that are 
non-spoilage, non-pathogenic and acidophilic, thriving in an environment 
with a pH of about pH 4 to about pH 5. While various euhygienic bacteria 
can be selected for use, preferred euhygienic bacteria include 
homofermentive bacteria able to produce either lactic acid or acetic acid 
as by-products of their glycolytic processes. Such euhygienic bacteria are 
thus able to create an environment favorable to their continued 
proliferation but unfavorable to the growth of undesired bacteria, i.e. 
Spoilage and pathogenic bacteria. 
Preferably, a desired euhygienic bacteria is selected from the genus 
Lactobacillus, and even more preferably from one or more of the following 
species: L. delbrueckii, L. leichmannii, L. jensenii, L. lactis, L. 
bulgaricus, L. helveticus, and L. acidophilus. In the most preferred 
embodiment of the invention, L. delbrueckii is the predominant desired 
bacteria. It is known that L. delbrueckii exists in several subspecies and 
the present invention includes the use of all subspecies, mutations, and 
genetic alterations to L. delbrueckii. 
Inoculation with euhygienic bacteria is preferably performed subsequent to 
other bacterial control measures being taken, for example, after dehairing 
the animal, applying an acetic acid spray wash, applying antimicrobial 
agents or after irradiating the food. Under proper environmental 
conditions, euhygienic bacteria proliferate and colonize the food surface, 
and in so doing, create a pH environment favorable to the continued 
competitive growth of the euhygienic bacteria. 
While not intending to be bound by theory, it is believed that one of the 
ways in which certain euhygienic bacteria act to extend the shelf life of 
meat is by lowering the pH on the surface of the meat to create a slightly 
acidic environment. The lowering of the pH on the surface of the meat 
creates an environment favorable to the growth of the euhygienic bacteria, 
but unfavorable to the growth of undesired bacteria. Thus, once a colony 
of euhygienic bacteria, such as L. delbrueckii, is established on the 
surface of a meat product, other forms of bacteria are effectively 
precluded from multiplying or are killed by the acidic environment 
produced by the euhygienic bacteria. 
In another embodiment of the invention, the inoculation of meat with 
euhygienic bacteria is done in combination with the inoculation of a food 
product either with antibiotics or with antibiotic producing bacteria, for 
example, Streptococcus Lactose or Pediococcus. Such bacteria are known to 
generate antibiotics toxic to spoilage and pathogenic bacteria. These 
later bacteria are capable of producing antibiotics toxic to undesired 
pathogenic and spoilage bacteria, but that are not toxic to euhygienic 
bacteria. It is also within the scope of the present invention that a 
euhygienic bacteria may be genetically engineered to acquire certain 
antibiotic properties. Thus, inoculation with such an euhygienic bacteria 
may actively kill certain undesired bacteria while proliferating on the 
surface of a food product to effectively inhibit and/or exclude the growth 
of other undesired bacteria. 
In another embodiment of the invention, the euhygienic bacteria used is a 
gram negative, sacrophilic, mesophilic, thermophilic bacteria, effective 
to competitively inhibit the growth of spoilage and pathogenic bacteria. 
In a particular embodiment of the present invention, an euhygienic 
bacteria of the genus Hafnia and more preferably from the species alvei is 
used either independently or in conjunction with L. delbrueckii. 
Although not intending to be restricted by current theory, it is believed 
that L. delbrueckii bacteria may be present on meat surfaces in a 
symbiotic relationship with other commensal euhygienic bacteria. For 
example, L. delbrueckii may proliferate on meat surfaces with Hafnia Alvei 
in such a relationship. Although Hafnia Alvei is known to be a common 
bacteria, a sub-species of Hafnia Alvei is known to be capable of 
relatively rapid growth at temperatures of about 5.degree. C. Under one 
theory, Hafnia Alvei initially colonizes the surface of a food product to 
create an environment conducive to the growth of L. delbrueckii. 
Therefore, the present invention includes the inoculation of meat with 
either Hafnia Alvei or L. delbrueckii, or a combination thereof, in order 
to competitively inhibit and exclude the growth of undesired pathogenic 
and spoilage bacteria. 
In a preferred embodiment, euhygienic bacteria such as L. delbrueckii 
bacteria is contacted with an animal carcass after the animal has been 
through one or more bacterial control measures to reduce the number of 
bacteria on the meat surface. For example, after an animal has been 
dehaired and its carcass has been conveyed through an acetic acid spray 
wash, the carcass is inoculated with an effective amount of the euhygienic 
bacteria, L. debrueckii. In such a manner, the inoculation with L. 
delbrueckii is more effective in inhibiting the growth of undesired 
bacteria due to the reduction of other bacteria on the meat surface. 
Certain acidophilic euhygienic bacteria, such as lactobaccillium, are known 
to grow well in acidic environments having pH ranges from 3 to 7. Fresh 
meat is known to have a pH of about 5.3 to about 7. At pH levels of about 
4.5 the majority of spoilage and pathogenic bacteria are either killed or 
their growth is severely inhibited and/or arrested. Contacting fresh meat 
with an effective amount of a weak organic acid, such as acetic or lactic 
acid, lowers the pH of the meat from about pH 3 and about pH 5 and 
preferably to about 4, thereby reducing the vast majority of 
non-acidophilic bacteria and creating an environment more conducive to the 
promoting the growth of acidophilic euhygienic bacteria. The acidification 
of the surface of red meat also has other beneficial effects. Organic 
acids act to maintain meat in a reduced state, thereby maintaining a 
desirable red color of the meat. The present invention therefore includes 
a method for creating an acidic environment on the surface of a meat 
product favorable to the growth of acidophilic euhygienic bacteria. 
It is to be understood that inoculation of ground food products may entail 
contacting euhygienic bacteria with portions of the food product which 
will not be necessarily "on the surface" of the food product. It is 
believed that euhygienic bacteria, even when present on the interior of a 
food product, such as ground beef, promotes the competitive inhibition 
and/or exclusion of the growth of undesired bacteria. It is further 
believed that the use of euhygienic bacteria is particularly useful in 
ground meat products incorporating vegetative matter, such as oat flour. 
The present invention also includes an unique method for tenderizing meat 
whereby meat is allowed to age for an extended period of time without 
spoiling. The aging of meat permits enzymes present in meat to degrade 
meat fiber, thus making the meat more tender. The freezing of meat retards 
or ceases such enzymatic activity. Irradiation of meat similarly destroys 
or retards enzymatic reactions that would otherwise occur. The present 
invention, because it allows for the maintenance of meat in a refrigerated 
environment for an extended period of time without spoiling, permits the 
natural enzymatic aging of the meat to proceed, producing meat of 
increased tenderness. In one embodiment of the present invention, meat is 
inoculated with an effective amount of euhygienic bacteria to inhibit 
and/or exclude the growth of undesired bacteria for a period of time 
sufficient to permit the natural enzymatic aging of meat without any 
coincidental spoilage of the meat. 
Another aspect of the present invention includes exposing euhygienic 
bacteria to a meat processing facility, or the equipment used in such a 
facility subsequent to the effective sterilization of such facility and/or 
equipment. In such a manner, the general environment of the meat 
processing facility is effectively exposed to or inoculated with 
euhygienic bacteria in order to competitively inhibit and/or exclude the 
growth of undesired pathogenic and spoilage bacteria. In this way, for 
example, the risk of unintended contact between meat products and 
undesired bacteria is kept to a minimum and the opportunity for undesired 
bacterial infection of meat is vastly reduced. The exposure or inoculation 
of a food processing facility with euhygienic bacteria can be accomplished 
in any manner which effectively reduces the risk of unintentional 
infection of a food product with undesired bacteria. This can be 
accomplished, for example, by first effectively sterilizing a food 
processing facility, or the equipment therein, by applying to the facility 
and equipment effective amounts and concentrations of organic acid 
solutions and/or other sanitizers, such as, but not limited to, chlorine, 
quaternary ammonia, and iodine based agents. After such sterilization, the 
facility and equipment therein is inoculated with an effective amount of 
euhygienic bacteria to inhibit and/or exclude the growth of undesired 
bacteria. 
It is to be expressly understood that the present invention can be used in 
combination with other bacterial control procedures. In particular, the 
dehairing of animals, or the spraying of animal carcasses with organic 
acid solutions, prior to the dispatching and slaughtering of such animals 
can be used to initially reduce the number of bacteria present in the meat 
slaughtering facility. Moreover, sanitation measures including the 
sterilization of knives used in the slaughtering process, changing of 
worker's gloves on a periodic basis during the slaughtering operation, 
disinfecting of slaughtering lines and maintaining personal hygiene 
requirements for workers, assists in the control of undesired bacteria 
proliferation. By using the present invention in combination with such 
other sanitation measures, and by maintaining meat in an environment 
cooled to about -1.degree. C.-7.degree. C. after the vacuum packing of the 
meat in plastic bags, it has been found that the shelf life of meat can be 
extended for up to 150 days without unacceptable growth of spoilage and 
pathogenic bacteria. The general object of the present invention is thus 
to create an environment that selectively favors the growth and 
proliferation of euhygienic hygiene bacteria over the growth of undesired 
bacteria. 
In one embodiment of the invention, a second inoculation with euhygienic 
bacteria is performed prior to the final packaging of meat products in 
oxygen impermeable wrapping such as a plastic bag. In this embodiment, 
meat is placed in plastic bags, contacted with euhygienic bacteria, and 
ambient air is then vacuumed from the bag and the bag is sealed. In such a 
manner, euhygienic bacteria colonize the meat within the substantially 
anaerobic environment of the vacuum packed bag. Food products, such as 
meat, treated and packaged as described above, can be placed in a 
refrigerated environment to further extend the shelf life of the food 
product. 
In another embodiment of the invention, a food product first inoculated 
with euhygienic bacteria is maintained in a temperature environment cooled 
to between about -1.degree. C. to about 7.degree. C., more preferably 
between about 1.degree. C. and 6.degree. C., and most preferably between 
about 2.degree. C. and 5.degree. C. It is preferable to maintain meat at a 
temperature above the approximate freezing point of meat (about 
-2.5.degree. C. to about -3.degree. C.) in order to avoid the damage 
caused by freezing meat and to avoid the killing or severe retardation 
and/or arrestation of euhygienic bacterial growth and proliferation. It 
will be appreciated that variations in temperature and periods of exposure 
may be utilized. However, lower temperatures and longer periods of 
exposure produce a greater depth of temperature penetration of the meat 
product and detract from the product quality. The present invention also 
includes the inoculation of food products with euhygienic bacteria 
genetically altered to grow and proliferate in low temperature 
environments. 
In some situations, the packaging of a food product may be necessary for 
the present invention to be used effectively, i.e., in order that 
euhygienic bacteria may effectively colonize the food product. For 
example, dependent upon several factors, including but not limited to the 
kind of undesired bacteria in the ambient environment, the type of food 
product, and other environmental conditions, a food product may require 
packaging in an oxygen impermeable plastic bag subsequent to inoculation 
with an effective amount of euhygienic bacteria. In general terms, 
environmental conditions must be created and maintained so that the 
natural selection and growth of euhygienic bacteria is favored over that 
of undesired bacteria. 
The present invention also comprises food products made in accordance with 
the various embodiments of the above-described method. In particular, the 
present invention includes a meat product having a shelf life of over 
about 40 days produced in accordance with the method comprising the 
inoculation of meat with an effective amount of euhygienic bacteria to 
competitively inhibit the growth of pathogenic or spoilage bacteria. The 
euhygienic bacteria are preferably selected either from the genus 
Lactobacillus and more preferably from the species L. delbrueckii, or from 
the genus Hafnia, and more preferably from the species alvei. In one 
embodiment, the meat is maintained in storage at a temperature environment 
of between about -1.degree. C. and 7.degree. C., more preferably between 
about 2.degree. C. and 7.degree. C., and most preferably between about 
3.degree. C. and 5.degree. C. 
Meat produced in accordance with the above-described method retains the 
color and odor characteristics associated with fresh meat for an extended 
period of time, such time period extending up to about 150 days from the 
date the animal was slaughtered. Because conventional methods of fresh 
meat processing do not allow for meat shelf life of over about 30 to 40 
days, numerous foreign markets for fresh domestic meat products remain 
effectively closed. Access to foreign fresh meat markets, for example, 
those of the Pacific Rim countries and Europe, necessitate the costly 
shipping of domestic meat products by air in order to have such products 
sold before spoilage occurs. The present invention extends the shelf life 
of fresh meat and meat by-products for up to about 150 days or more 
without the undesired proliferation of spoilage or pathogenic bacteria. 
Because of this extended shelf life, foreign markets for domestic fresh 
meat products are made accessible, allowing for the economic shipment of 
fresh meat by boat, rather than by airplane. 
The following test results are provided for purposes of illustration and 
are not intended to limit the scope of the invention. 
EXAMPLES 
Example 1 
An animal was slaughtered in a process in which the animal was first 
stunned, de-haired, ex-sanguinated, dehided, conveyed through an acetic 
acid spray wash (acetic acid present in a 0.5-1.5% solution) and 
fabricated. After application of the acetic acid spray, the animal carcass 
was sprayed with a diluted solution containing L. delbrueckii bacteria 
formulated by growing L. delbrueckii in 750 ml of growth broth for 24 
hours at a temperature of 35.degree. C. and diluting the resulting 
solution to attain a 1 part in 10 solution. Meat from the animal carcass 
was then vacuum packed in a plastic bag to remove essentially all oxygen 
and the bag was heat sealed. The meat was stored in a temperature 
environment of about 5.degree. C. for 150 days. After 150 days, the bag 
was opened and a total bacterial plate count was performed. An analysis of 
the bacteria present on the meat was performed indicating that L. 
delbrueckii bacteria had essentially colonized the entire meat surface. 
The meat had color characteristics similar to meat that had been 
slaughtered in a conventional fashion and refrigerated at 5.degree. C. for 
less than 30 days. 
Example 2 
While various embodiments of the present invention have been described in 
detail, it is apparent that modifications and adaptations of those 
embodiments will occur to those skilled in the art. However, it is to be 
expressly understood that such modifications and adaptations are within 
the scope of the present invention as set forth in the following claims.