CA1050810A - High-moisture shelf-stable animal food and method for preparing same - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A shelf-stable, high moisture animal food is disclosed which is resistant to microbial spoilage without the need for sterilization or refrigeration and is characterized by its high palatability. The animal food is based primarily Upon protein-aceous materials and utilizes a preservation system containing glycerol and a glycol which is propylene glycol or butylene glycol which combination has been found to act in unexpected concert in affording stability.

Description

This invention relates to animal foods and more par-ticularly to animal foods of the shelf-stable, high moisture variety.
Prior to the 1960's, animal foods were sold either in dry or canned form. The dry variety of animal foods usually con-tain less than 10% moisture and hence do not require s-terilization procedures or refrigeration in order to render them resistant to microbial decomposition. The dry animal foods, however, are gen-erally characterized by their low degree of palatability, it being found that as a general rule palatability is enhanced at higher moisture contents.
Canned animal foods enjoy a significant degree of palatability owing primarily to their high moisture contents, typically in the area of 75%. However, this hiyh moisture content necessitates the sterilization o such products, generally by re-torting and refrigeration once the can is opened. Thus, canned foods involve significant processing costs and a lack or consumer convenlence.
A significant contribution in the animal food field was made by Burgess, et al. in United States Patent 3,202,514 assigned General Foods Corporation. Therein is described an intermediate-moisture animal food (15-30% water) based principal-ly upon proteinaceous meaty materials which product is shel-stable and resistant to microbial decomposition without the need for sterilization, refrigeration or aseptic packaging. The meaty animal food is stabilized by "wa~er soluble solutes" principally sugar. The function of these solutes is to bind up available water in which microorganisms grow.
While the product of Burgess, et al. represented a significant contribution to the state of the art, the need for improvement in this area has been and continues to be recogni~ed.
More specifically, prior art workers have attempted to improve the palatability o~ such products such that they achieve parit:y in ~ L~SOB~O
this area with the more palatable canned animal ~oods~ Palat ability improvement may tace a variety of forms such as the overt addition of enhancersy the utilization of greater amounts of meaty materials and the like. The provision of higher moisture products is desirable since there is evidence of increased palatability with increased moisture~
The attainment of ~uch higher moisture content product~
so as to derive any palatability improvement attendent therewith, however~ may be counter-productive. Following prior art teaching~, the stabilization of products having a moisture content in the 35 to 60~ range has heretofore necessitated the use of significantly greater amounts of stabilizing agentsO The increased amounts of stabilizing ingredients may indeed negate the expected palat-ability improvemant in that some qtabilizers are per ~e unpalat-able at high concentrations and also because the proportionate total increase in these ingredients will often result in a corre-sponding decrease in the amount of palatable and palatability improving materials which may be utilized in the product. Utiliza-tion of high acidity to achieve stability and hence obviate the -~
~0 above problems to some degree has not proven successful in that ~uch systems are generally found to be unpalatable to some pets, especially dogs.
There is a need for high moisture animal food products in the range of 35 to 60% water which are resistant to microbial ;~
spoilage without resort to sterilization or refrigerationt yat which are characterized by a high degree of pala~ability. There is particularly a need ~or a shelf-stable high moisture animal food having a palatability equivalent to premium canned animal foods of higher moisture contents.
It has now been found that an animal food product can be prepared having a moisture content of 35 to 60~ by welght and containing as preservative agents glycerol and either propylene glycol or butylene glycolO The animal food composition is based 1~()8~
primarily upon a matrix of proteinaceous materials and will fuxther desirably contain flavorants, vitamins, minerals and the like to achieve a nutritional, palatable product.
According to the invention there is provided a palatable, shelf-stable high moisture animal food composition adapted to be packaged without resort to sterilization and stored for extended periods of time without the need for refrigeration, said compo~i-tion comprising a cooked matrix of proteinaceous materials normal-ly capable of supporting microbial growth, said matrix having dispersed therein a ~olution of stabilizing ingredient~ compris2d of a mixture of from about 4 to about 12~ of a glycol which i~
propylene glycol or butylene glycol and from 4 to about 15%
glycerol on a weight basis sufficient to maintain the ~w of said composition below about 0.93, said matrix ~urther having an edible anti-microbial agent in intimate contact therewith, the levels of said stabilizing ingredients and said agents sufficient to main-tain said composition resistant to microbial growth, said animal food composition having a substantially neutral pH and a moisture content between about 35% to 60~ by weight.
There is also provided a process for preparing a highly palatable, high moisture shelf-stable animal food composifion adapted to be packaged without resort to sterilization and stor~d for extended periods of tim,e without refrigeration, said proce~s ~omprising forming a mixture comprised of raw proteina~eouQ
materials, stabilizing ingredients comprised of glycerol and a glycol which is propylene glycol or butylene glycol and an edible anti~miarobial agent into a desired shape, heating said shaped~
mixture at a temperature above 150F. for a period of time su~ficient to cook said proteinaceous materials and cooling said shaped and cooked mixture, said composition having a moisture con-tent of 35 to 60% by weight, a pH of from about 5.5 to 7.5 and an ~w below about 0.93, the level of said stabilizing ingredients and anki microbial agents sufficient to maintain said composition ~ ilLiD5~8~
resistant to microbial growth.
The product of this invention is generally shel~-~table, i.e., resistank to the growth of microorgani~ms even after extend-ed periods of storage without khe need for sterilixation tech-nigues, refrigeration, or special packaging procedure~.
The preerred product of this invention is characterised by its normally extremely high palatability to animals, especially dogs, to the point where it is as readily accepted as premium canned products containing signi~icantly higher moistuxes.
While not believed at ~his time to be per se critical to the achievement of the desirable characteristics of the pro-duct~ of this invention, a pre~erred unique process for preparing such products i9 disclosed involving the steps of first forming the raw materials into a desired shape, cooking the product, cool-ing and packaging.
The ability to achieve khe high moisture, highly palat-able product of this invention is predicated largely upon the presence of a mixture of glycerol and either propylene glycol or butylene glycol (1,3-butanediol) in the product. It has been ~0 discovered that the combination of glycerol and propylene gly~ol or butylene glycol in a 35% to 60~ moisture system acts in an unexpected fashion in its preservative effect. It i9 al50 be-lie~ed that the mixture of these ingredients may per e lend ~gnificantly to the high palatability of the product of thi~ in-vention by effectively increasing the apparent moisture perceiv~d by pet~ upon consumption of the product and also by }ending a de-sirable texture to the final product.
The preservation of moisture-containing foods ~r micro~ial decomposition is dependenk upon a variety of ~actors and mechanisms whose interaction is not always ~ully understood.
Some basic mechanisms however are generally well accepted and can be listed.
Microbial grow~h is largely dependent upon the amount ~ 5~
of mois~ure in a sy~tem available as a growth medium. The typical expre~sion of this is the water activity or Aw of a product. The Aw is equal to the vapor pressure of wa~er ln the sy~tem over the vapor pressure of pure water at the same temperature~ Theoretical-ly, the Aw of a given qys~em can be lowered to ~uch a degree that the available water is insuf~icient to ~upport any microbial growth. Since ~he Aw of, for exa~ple, meat product~ used in pra-paring animal foods is sufficiently high to support a host of microbial activity, the basic mechanism in stabilizing such pro-ducts is to lower this na~ural Aw to the requisite level. Thi3 isaccomplished primarily through the addition of materials commonly referred to as water binders which have the ability to tie up water otherwise available for growth by altering the osmotic pressure of the system.
It i8 al~o common practice in the preservat:ion of moisture-containing foods to employ an antimicrobial agent thereln to insure that the product is kept in a microbial-free skate, typically where the Aw of the system is not lowered to the absolute point below which organisms will grow. Typically these antimicrobial agents take the form of antimycotics which act specifically against mold growth.
Lastly, the provision of an acid medium of sufficiently low p8 will independently aid in preventing microbial decomposi-tion owing to the fact that many organisms cannot survive in ~uch an environmentO Howev~r, since the requisite pH for achieving thi~ prokection is generally so low as ~o xesult in an unpalat-able, as well as detrimental, system in some cases, the utiliza-tion of pH as a primary protective is rarely e~ployed.
~ he above preservative mechanisms generally are present in combination in a given food system and exert a combined ~tabi-lizing effect. Thus, for example, the prior art products general-ly employ sugars as water binders together with antimycotic~ such as sorbic acid and it3 salt.
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~o~ o Glycerol is known as a water binder and hence its pre-servative effect is a result of its ability ~o lower the Aw of the food sy~tem. Glycerol, however, has no known antimicrobial properties. Propylene glycol (or butylene glycol) is favored among many processors since it possesses a dual function. It i5 a water binder and also has antimycotic properties. Thus, the preservative effect of propylene glycol (or butylene glycol) is a result of its ability to suppress the Aw of the system to a avor-able point and at the same time to act specifically in combatting mold growth.
It has been found that the combination of glycerol and propylene glycol or butylene glycol coracts in an unexpected fashion in stabil-izing the products of this invention, i.e., having between 35 to 60~
moisture. We have found that glycerol while possessing no known antimicrobial activity is somehow able to potentiate or synergiz,e the antimicrobial effects of propylene glycol or butylene glycol.
It is not known at this time whether the glycerol acts in specific concert with the glycol or whether the glycerol has some effect on the food system which makes the glycol unexpectedly more effective in its antimicrobial function.
It is important to point out that this heightened ef~ect is not explainable by reference to glycerol's known Aw suppressing or water binding effect. Indeed, it is found that in systems hav-ing equivalent moistures and Aw's and otherwise equivalent in-gredients, mixtures of glycerol and propylene glycol or butylene glycol afford stability where the glycol does not.
The significancy of this discovery is readily apparent since it will generally allow the use of smaller amounts of pre-servative ingredients than expected and ~hereby allowing the 3Q utilization of increased amounts of other palatable, palatability improving and nutritional ration-balancing ingredients. Further, it allows the use o~ less propylene glycol or butylene than hereto-fore thought necessary and henca precludes any possible adverse -6~

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palatability effects of high levels of -this material.
These considerations are especially important in h~gh moisture system~ ~uch as th~ present for two primary reason3.
The provisiQns of higher moisture per se takes away rom the available room for the provlsion of palatable ingredient~ ~uch ~s meats and other nutritional and palatable additives. ,ience, were an inordinately high level o pre~ervat:ives required this would even further agyxavate this problem. Secondly, it is found that even at similar Aw's a higher mois~ure sy tem will spoil where a lower moisture sy~tem would not. Thus in formulating a high moisture animal food, the mere matching through, say, additional water binder~, of the Aw of lower moisture, stable product may not be sufficient to insure protection in the higher moisture product. Thus, even more than proportionally expected water binders or antimycotic ingredients would have to be employed to achieve stability. Hence, the cooperative action of glycerol and propylene glycol or butylene glycol in the present invention i8 0 significant importance in keeping within reasonable bounds the amount of preservative material needed for stability, thereby in-creasing the amount of other desired ingredient~ which can be ~m~
ployed and minimizing any adverse palatability effects of th~
~tabilizing ingredients.
While the presence of the glycerol glycol combination may per se totally inhibit microbial growth in some of the pro-ducts embraced by this invention, it has been found desirable to employ an additional antimicrobial agent other than propylene glycol or butylene glycol, especially an antimycotic so as to com-pletely insure that prevention o~ microbial spoilage o~ the p~o-duct is achieved. Preerred in this respect is potassium sorbate which will typically be employed in the range of 0.05 to 0.6% by weight of the food product. Examples of others which may be em-ployed either singly or in combination are benzoic acid, sodium benzoates, propionic acid, sodium and calcium propiona~e, di-~05~
ethyl pyrocarbonate, menadone sodium bisulfite (vikamin ~), caproic acid, caprylic acid, levulinic acid, sorbic acid, calcium sorhate, parahydroxy benzoic acid esters and the like. It will be apparent to those skilled in the art that the above disclosed co-action of glycerol and propylene glycol or hutylene glycol may indeed allow the use of lesser amounts o~ the above-listed materials than normally employed. Whera potasslum ~rbate is employed, ~his reduction in the requi~ite level will have a sig-nificant effect on palatability, potassium ~30rbate being decided- ~
10 ly unpalatable to mos~ animals, especially dogs, as its level i9 ~-increa~ed.
The antimicrobial agent i~ to be in intimate contact with the animal food product. While it will generally be a com-ponent of the starting mixture, it is also possible tb spray or otherwise coat the antimycotic onto the otherwise fini~hed pro-duct. Tf the product i9 to be in intimate contact with a packag~
ing material, it is possible to have the antimycotic present on the contacting surface of the packaging material itself.
The pH of the product of this invention is substantially neutral and i9 not critical ~ se but is subject to restric-tions based primarily upon palatability. In general, a p~ below about 5.5 is not preferred by some pets, such as dog~ and hen~e the pE of the product will typically be above this level, say above 5.8. Upper limits for pH are subject to considerations o~
taste and in general will not exceed 7.5 to 8Ø A preferred pH
is in the order o~ 6.0 to 6.5.
The product of this invention has a moisture content ln the range of 35% to 60% by weight, preferably from 40 to 50% a~d most preferably rom 40 to 45% by weight. Typically, th~ raw ingredient~ utilized in the animal food composition, especially meats/ will have the requisi~e moisture associated therewith ~u~h that the overt addition of water is not needed. Eowever, added water i9 clearly not precluded by this invention and may lndeed 8~

~ ~ 8 be necessary in some cases in order to achieve the final pro duct moisture desired.
Thus the animal food product of this invention, hav-ing between about 35/O to 60% mois~ure is rendered shelf-stable and resistant to microbial decomposition by the provision of materials which will lower the Aw of the product to the re-quisite level and an edible antimicrobial agent or agents.
The Aw of the product of this inven-tion is critical in that it mus-t be below about 0.93. Products having Aw's about this, given the high moisture and the desire -to avoid highly acidic medium and excessive amounts of antimic:robial `
agents, could be subjec-t to microbial decomposition. In a preferred embodiment of this invention the Aw will be below abou-t 0.90.
The glycerol/glycol combination of this invention may itself provide the requisite water binding effect to result in the desired Aw and hence will constitute the sole stabilizing ingredients (apart from the additional antimycotic). Typi-c~lly, where products between about 35 to 40% moisture are desired, it is possible to achieve the requisite Aw, i.e, below .93 and preferably below 0.90 through the sole use of about 16 to 20% by product weight of the glycerol/glycol mixture. Where higher moisture products are contemplated, while it may be possible to utilize only the glycerol and propylene glycol, or butylene glycol, it is preferred to employ other well-known water binders to aid the glycol/glycerol mixture in suppressing the Aw of the system. Thus~ ingredients such as sodium or potassium chloride or other polyols (e.g., sorbi-tol) may be g ~;.

employed as well as other water soluble or partly soluble materials capable of effecting a ris~ in the osmoti.c pressure in the food system. Sugars, as defined in IJnited S-tates Patent 3~202,514 to Burgess et al. may also be employed though their use at levels above about 10% by weight of lhe final product and preferably above 5%, is not preferred due to the -9a-~ '~, .
~ ~ . . . .
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tendency of these materials to undergo non-enzymatic browning reactions resulting in poor appearance and palatability, their excessive sweetness and the fact that they themselves are an excellen~ medium for microbial growth.
Typically these auxiliary or complementary water binders will be present a~ a total level of from 1 to 10% by weight with sodium chloride being a preferred additive at a range of from 1 to

2% by weightO
Thus the key to the present invention is the presence of a combination of glycerol and propylene glycol or butylene glycol in the food product. The discovery of the co-action of these materials in a 35 to 60% moisture system in providing an antimicrobial effect has the significant advantaye of allowing the employment of lesser amounts of these materials, e~pecially the glycol, than theoretically needed. This in turn results in the provision of a stable product based solely on the glycerol/glycol preservative effect (in conjunction with an antimycotic) or as will typically be the case/ a shelf-stable product wherein the above co-action or potentiation results in significantly less 2~ amounts of other Aw suppressing and antimi~robial ingredients.
~he net result of these findings allows the utilization of high moistures and sufficient amounts of palatable and nutritional in-gredients in achieving the goal of a highly palatable shelf-stable animal food product.
The product of this invention will preferably contain from about 10% to about 25% by weight of the combined glycerol and glycol system and preferably from about 12% to about 18%~ '~he glycerol will typically range from about 4% to 14% hy weight, pre-ferably 7-11% and the propylene glycol, butylene glycol from 4, preferably 5, to 10% by weight, more preferably from 8 to 10~.
An important aspect of this invention is that the discovery of the potentiating or cooperative effect o the glycerol on the highly desirable stabilizing properties o the glycol allows the enjoyment ~"; :

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Qf such propertie~ at levels of glycol which do not detract from the palatability of the food product, it being found that ylycol levels above 10% and especially near 15 to 20~ begin to drop off in palatability. Glycerol and glycol levels falling within the abo~e-mentioned ranges are found to yield the unexpected coopera tive effect. In the most preferred embodiment of this invention, the ratio of propylene glycol to glycerol will be approximately 1:1 on a weight basis. However, the ratio may range from about 4:1 to about 1:3.
Wholly apart from the above-mentioned benefits of the combination, it is believed a~ this time that the glycerol and propylene glycol or butylene glycol have an important function in rendering the products of this invention as palatable or nearly as palatable of the premium canned animal foods containing fully any-where from 15 to 40% more moisture. It is theorized that these ingredients are somehow perceived by the consuming pet as actual moisture, e.g., a moisture mimetic effect and thereby heighten the ;
animal's acceptance of the product.
The product of this invention comprises a moisture-con~
taining, cooked matrix of proteinaceous materials normally capable of supporting bacteriological growth having dispersed throughout water binding inyredients sufficient to achieve an Aw of below about 0.93, the ingredients comprised of glycerol and propylene glycol or butylene glycol and further having in contact therewith an antimicrobial agent, the level of the water binding ingredients and antimicrobial agent being sufficient to keep the product in a microbial-free state and resistant to microbial decompositionA
Thus the level of antimicrobial agents and Aw lowering ingredients will be balanced to achieve stability at any given moisture con-tent. For example, it may be necessary to employ only a minoramount of anti~icrobial agents where the Aw of a given moisture content system is at a level nearly precluding all growth. Con-versely, larger amounts of antimicrobial agents may be needed in ~5138~
a moisture containing system wherein the Aw is closer to 0.93.
The term proteinaceous material is mean-t to include proteinaceous meaty materials and non~meat protein materials. It is preferred that the pro~uct of this invention contain protein~
aceous meaty material. The ~erm proteinaceous meaty material refers to the group consisting oE meat, meat by~products and meat meal, as well as mixtures of these. The term meat is understood to apply not only to the flesh of cattle, swine, sheep and goats, but also horses, whale and other mammals, poultry and ~ish. The term meat by-products is intended to refer to those non-rendered parts of the rarcass of slaughtered animals including but not re-stricted to mammals, poultry and the like and including such in-gredients as are embraced by the term "meat by-products" as defin-ed in the 1974 o~ficial publication o the Association of American Feed Control Official Incorporated. Likewise, the term meat meal refers to the finely ground, dry rendered residue from animal tissues, including those dried residues embraced by the term "meat meal" as defined by the aforesaid Association. Indeed, the terms meat, meat by-products and meat meal are understood to apply 2~ ~o all of those animal, poultry and marine products defined by / said Association.
The proteinaceous meaty material will preferably con-stitute a significant portion of the prod~lct of this invention, typically greater than about 30% by weight and preferably greater than 5n%. A typical range for such ingredient is about 30% to 80% by weight.
~ part from the pro~einaceous meaty material and the preservation system, the product of this invention may optional-ly, though preferably, contain other proteinaceous ingredients, texturizers, ~itamins, minerals, colorings, fla~orants and the like.
Non-meat proteinaceous materials, i.e., pro~ein sources other than the proteinaceous meaty material are preferably employ-1 015i[)B3LO
ed to achieve a fully balanced, nu-tritional feed ration. Typical-ly the protein will be derived from a veyetable protein source such as soybean, cottonseed, peanuts and the like. The protein may be present in the form of meal, flour, concentrate, isolate or the like. A preferred protein source is soy. Additional protein may be derived from milk products such as dried buttermilk, dried skimmed milk, whey, casein and other like protein sources, such as eggs or cheese.
While these additional protein sources are generally mixed with the starting ingredients, all or part of some of these protein materials may be used to coat the otherwise formed final product o~ this invention, as will be described in more detail hereinafter.
Texturizing agents may be added at minor weight per cents if desired, although it is found that the utilization of the propylene glycol or butylene glycol and glycerol preservative system will generally be sufficient to impart the necessary plasticity and texture to the final product.
The animal food composition will also desirably contain a binder material in an amount effective to keep the formed com-position coherent and shape-retaining after cooking. ~he binder material may be of the proteinaceous or farinaceous variety such as egg albumin, wheat flour, corn flour and the like or may be a polymeric carbohydrate binder such as sodium carboxymethylcellu-lose, gelatin, a-cellulose and the like. It is found that corn flour yields the most desired binding effect while not adversely affecting the texture~ appearance or palatability of the animal food. The binder is preferably employed from about 3% to 10% by weight and most preferably from about 5 to 8%.
Additional ingredients in the preferred product will in clude vitamins, minerals, colorings and flavorants. Fat or oil may be desirably added, preferably in the source ingredients al-though it may be sprayed or coated on the final formed product.
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, ~61 5~
The product oE this invention is adapted to be packaged under non-sterilizing conditions and hence represents a signiEi-cant processing advantage as well as being convenient to the purchaser. Typical packaging materials are of the moisture-imper-meahle type such as cellophane, polyethylene and the like.
The product of this invention may be prepared in a variety of ways. However, it i5 most preferred to utilize a pro cess wherein the ingredients are ~ormed into a desired shape, cooked to effect pasteurizationt cooled and packaged.
Thusr in the preferred process of this invention, the meaty ingredients, the liquid ingredients (e.g., water, propylene glycol or butylene glycol, glycerol) and the remaining dry ingredients, are separately mixed in suitable blenders. The three mixtures are then mixed together to form the raw animal food matrix. The matrix is then formed into any desired shape and cook-ed at elevated temperatures, say, above 150F. After cooling, the product is packaged preferably in a moisture-impermeable material.
In the preferred process/ the raw animal ood matrix may be formed into any number of desired shapes such as meatball-shaped, hamburger-shaped, cylindrical and the like. In cooking the shaped matrix, it is desired to avoid the use of excessive temperatures which would cause degradation of the product.
Typically, cooking will take place at a temperature ranging from lS0 to 200F. Various cooking apparatus may be used such as con-ventional ovens, infra-red ovens, micro-wave cookers, deep-fat frying and the like. Preferred, however, is the cooking with moist heat in a high moisture oven. Cooking time will generally be in the order of about 2-10 minutes depending upon the source and ex-tent of heat applied.
The cooked product, once cooled, is packaged in amaterial relatively impervious to moisture. Foil or fo:il/paper pouches, canisters and the like may be employed.

~5Ci 81~
It has also been found that it may be desirable to firstapply a coating material to the formed matrix prior to cooking.
The coating, typically of the arinaceous or prcteinaceous type, will serve to aid in retaining moisture and fats during cooking.
The coating may be applied in dry form by tumbling the formed product in a finely divided coating material, or in li~uid form by spraying a liquid mixture of the coating onto the surface of the formed product. Preferred among coating materials are starches and soy isolate. ~here proteinaceous coatings are employed, an added advantage is obtained due to ~he provision of this nutri-tional protein source. The coating may also serve in imparting a desirable meat-like texture to the final cooked product. In this respect, it is found that spraying a solution of glycerol, propylene glycol or butylene glycol or a combination thereof will result in a desirable texture and appearance in the final product.
This coating may be employed in lieu of or in addition to the above-mentioned coating.
While the above-desired process is preferred, it is also possible to manufacture the product of this invention by more or less conventional methods such as set forth in United States Patent 3,202,514. Thus, the meaty ingredients may be first separately heated to above about 150F. and preferably be-tween 180F. and 220F. and then mixed with the remaining in-gredients, which ingredients may or may not have been separately heated. The combined mixture is ~hen heated, cooled to ambient temperatures and formed into a desired shape and packaged.
In order to more fully describe the present invention, the following operative examples are presented for illustrative purposes.
EXAMPLE I
The following ingredients were utilized in preparing the product of this invention.

~:

~ t Ingredients A B
Meat 61.5 61.5 Glycerine 9-0 9 0 Propylene glycol 8.8 0 Butylene glycol 8.8 Corn flour 7.7 7-7 Dextrose 4.0 4.0 Soy concentrate 3.0 3.0 Sodium chloride 1.3 1.3 Potassium sorbate 0.4 0-4 Water 0.3 0-3 Mineral supplement 2.2 2.2 Soy isolate, colorings, flavorings, vitamins, minerals 1.8 1.8 The meat, glycerine, propylene glycol or butylene glycol and water; and the remaining ingredients were first separately pre-mixed at ambient conditions. The mixtures were then blended together to form a raw matrix and ~he matrix was then formed into discrete pieces using a former.
The soy isolate was then coated onto the formed products by tumbling the product in a finely-divided form of the coating.
The coated products were then cooked in a high moisture steam oven at 250F. for about 15 minutes. The products were then cooled and packed in a pouch made of polyfoil/paper/polyfoil.
The resultant produc-ts were found to be completely free from bacterial growth even after 6 months of storage at ambient conditions. Tests were conducted wherein organisms were directly inoculated into the product, yet no growth occurred even after 6 months. The product A had a moisture content of 41%, a pH of 6.2 and an Aw of 0.91. The product B had a moisture content of about 45% and an Aw of 0~92O

l'he product A was fed to dogs in a controlled study .

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against the leading superior canned dog Eood product. The products were equally preferred by the animals.
EXAMPLE II
,. _ % By weight Ingredients A B
__ Meats 73.72 73.72 Glycerol 9-00 9~00 Propylene glycol 5.80 0 ~utylene glycol 0 5.8 5~1t 2.60 2.60 Corn flour 3.00 3.00 Caseinate 2.50 2.50 Potassium sorbate 0.43 0-43 Silicon Dioxide (binder~ 1.00 l.00 Vitamins, minerals, color l.9S 1.95 The meaks are cut and extruded into 1/8" diameter strands to which is added a warmed solution of the glycerol, propylene glycol and colors. The remaining ingredients (except corn flour) are blended with the meat mix at near 32-3~F~ The matrix was formed into meatballs using an Accupat former and were then dusted with the corn flour. The meatballs are cooked in a steam retort at 250F., 15 psig. steam for 10 minutes and packaged.
EXAMPLE III
.
Same as Example I except the coating utilized was powdered starch. The product was equally preferred by dogs when tested against a premium canned dog food.
_ PLE IV
As in Example I except that no coating was utilized.
EXAMPLE V
Same as Example I except that the coated product was cooked in an infra-red oven for 2-3 minutes.
EXAMPLE VI
A controlled experiment was conducted to display the 9LC~5~
stabili~ing co-action of glycerine and propylene glycol.
The formula of Example I was varied slightly to achieve the following samples and preservatives:
Sample I - 17% glycerol Sample II - 8~ propylene glycol Sample III - 9% glycerol, 8~ propylene glycol Sample ~V - 6% glycerol, 6% propylene glycol (no dextrose) Sample V - 17% propylene glycol All samples had a moisture content of 40% by weight.
The Aw's respectively were 0.90, 0.93, 0.90, 0.92 and 0.90.
The samples were ground and 25 grams of each were placed in jars and inoculated with Staph. sp. A. niger and A. glaucus.
Samples were tested with the following results:
Sample I - Mold growth & Staph. growth at 8 days Sample II - Staph. growth at 8 days Sample III - No growth Sample IV - No growth Sample V - No growth Sample I shows that glycerol, while an effective Aw suppressing agent, has no antimicrobial properties. Sample II
shows that the 8% propylene glycol was insufficient to deter microbial growth. Samples III and IV, however, display the un-expécted inhibitory action o the propylene glycol.
Samples III and IV show that even at relatively similar Aw the glycerol is somehow able to alter the system or the action of the propylene glycol i~self such ~hat the product is rendered stable. This effect, as can be seen, is wholly apart from any Aw lowering effect the glycerol has. Example V, while stable, was undesirable in that the large amount of propylene glycol resulted in a product of poor palatability relative to~premium canned pro~
ducts and those samples utilizing 8~ propylene glycol.

lOSl)B lLO
E ~PLE VII
As in Example I with 0~2~ potassium sorbate. Products were resistant to bacterial decornposition as tested by positive inoculation oE organisms.
The product of this invention is thus a highly palatable, high moisture product, yet which is resistant to bacterial decom-po~ition primarily through the use of amounts and ~types of stabil- :
izers which do not detract from ~he significant palatability improvement.
While this invention has been described with reYpect to specific examples and preferred modes of practice~ it will be apparent to those skilled in the art that various modifications and improvements are ascertainable without departing from the scope ;-.
and spirit of the invention as defined by the appended claims.

Claims (26)

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A palatable, shelf-stable high moisture animal food composition adapted to be packaged without resort to steriliza-tion and stored for extended periods of time without the need for refrigeration, said composition comprising a cooked matrix of proteinaceous materials normally capable of supporting microbial growth, said matrix having dispersed therein a solu-tion of stabilizing ingredients comprised of a mixture of from about 4 to about 12% of a glycol which is propylene glycol or butylene glycol and from 4 to about 15% glycerol on a weight basis sufficient to maintain the Aw of said composition below about 0.93, said matrix further having an edible antimicrobial agent in intimate contact therewith, the levels of said stabil-izing ingredients and said agents sufficient to maintain said composition resistant to microbial growth, said animal food composition having a substantially neutral pH and a moisture content between about 35% to 60% by weight.

2. The composition of claim 1, wherein said proteinaceous material comprises proteinaceous meaty material.

3. The composition of claim 2, wherein the moisture con-tent of said composition is from about 40 to about 50% by weight.

4. The composition of claim 3, wherein the ratio of glycol to glycerol is from 4:1 to 1:3 on a weight basis.

5. The composition of claim 4, wherein said pH is from about 5.5 to 7Ø

6. The composition of claim 5, wherein said proteinaceous meaty material constitutes greater than 50% by dry weight of said product.

7. The composition of claim 6, further comprised of vegetable proteinaceous material.

8. The composition of claim 7, wherein said vegetable proteinaceous material is present at a weight level of between 3% and 15% of said composition.

9. The composition of claim 8, wherein said vegetable proteinaceous material is soy.

10. The composition of claim 3, further comprised of a substantially continuous coating of fat or oil.

11. The composition of claim 3, further comprised of a substantially continuous cooked coating of a material selected from the group consisting of proteinaceous material, farinaceous material and mixtures thereof.

12. The composition of claim 11, wherein said coating material is proteinaceous material.

13. The composition of claim 3, further comprised of a substantially continuous coating of a material selected from the group consisting of the glycol, glycerol and mixtures thereof.

14. The composition of claim 3, further comprised of an effective level of a binder material incorporated within said matrix.

15. The composition of claim 14, wherein said binder material is a farinaceous material.

16. The composition of claim 15, wherein said farinaceous material is corn flour present at a level of about 5% to 10% by weight of said composition.

17. The composition of claim 9, wherein said pH is from 6.0 to 6.5.

18. A process for preparing a highly palatable) high moisture shelf-stable animal food composition adapted to be packaged without resort to sterilization and stored for extend-ed periods of time without refrigeration, said process compris-ing forming a mixture comprised of raw proteinaceous materials, glycerol and a glycol which is propylene glycol or butylene glycol in a total amount of about 10 to 25% and wherein the ratio of the glycol to glycerol is from about 4:1 to 1:3 by weight, and an edible antimicrobial agent into a desired shape, heating said shaped mixture at a temperature above 150°F. for a period of time sufficient to cook said proteinaceous materials and cooling said shaped and cooked mixture, said composition having a moisture content of 35 to 60% by weight, a pH of from about 5.5 to 7.5 and an Aw below about 0.93, the level of said stabilizing ingredients and antimicrobial agents sufficient to maintain said composition resistant to microbial growth.

19. The process of claim 18, wherein said composition has a moisture content of 40% to 50% by weight.

20. The process of claim 19, wherein said shape mixture is heated at temperatures between about 150 and 250°F. in a high moisture environment.

21. The process of claim 20, wherein said shaped mixture is substantially continuously coated with fat prior to heating.

22. The process of claim 21, wherein said shaped mixture is coated with fat by applying said fat in heated, liquid form to said mixture.

23. The process of claim 20, wherein said shaped mixture is substantially continuously coated with a material selected from the group consisting of farinaceous and proteinaceous materials prior to heating.

24. The process of claim 23, wherein said material is soy.

25. The process of claim 24, wherein said shaped mixture is coated by applying said soy in a dry, finely-divided form to said shaped mixture.

26. The process of claim 25, wherein said mixture is further comprised of a farinaceous binder material.