CA1130632A

CA1130632A - Expanded pet food product and method of producing sme

Info

Publication number: CA1130632A
Application number: CA340,272A
Authority: CA
Inventors: Victor A. Lowe
Original assignee: Carnation Co
Current assignee: Carnation Co
Priority date: 1979-02-23
Filing date: 1979-11-21
Publication date: 1982-08-31
Also published as: GB2041717B; FR2449410A1; FR2449410B1; GB2041717A

Abstract

ABSTRACT OF THE DISCLOSURE
An expanded pet food product having a moisture content of about 20%-30% by weight and a spongy, compressible cellular structure is made by combining a mix of dry ingred-ients containing farinaceous materials, proteinaceous materials and dry bacteriostatic materials with a blend of liquid ingredients containing an edible acid, a liquified fat or oil, a liquid bacteriostatic agent and water, and passing said admixture into an expander where it is subjected to mechanical work, shear, heat and pressure. The hot admixture is extruded through a die plate into a zone of lower pressure to cause the extrudate to expand. As the extrudate passes through the die plate it is cut into particles of desired length and promptly contacted with a water spray to reduce its temperature and control the amount of moisture loss from the particles. The cooled extrudate particles are coated first with an edible fat or oil and then with a solution containing an antimycotic, water and flavoring material.
The thus coated product is then packaged.

Description

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The present invention relates to a pet food product having enhanced palatability and excellent storage stability. More particularly, the invention relates to a so~t, intermediate moisture dog food product characterized ~y an expanded, cellular interior and having a pliant sealed surface.
Pet food products, in particular dog foods, are marketed in three common forms: dry products, which have a moisture content of ahout 10% ~y wèight; canned products, which have a moisture content of a~out 70% ~y weight, and semi-moist or intermediate moisture products, which have a moisture content intermediate that of dry and canned products, typically ~etween a~out 2a%-5n% ~ weight. While dry pet food products have excellent nutritional properties and superior storage and stability characteristics, they suffer from th~ disadvantage that ~ecause of t~eir hard, ~rittle texture t~ey are generally less pala~a~le to animals than the canned and intermediate moisture products. ~hile canned pet food products are readily accepted ~y animals, such products are su~ject to micro~iological decomposition unless packaged in hermetically sealed containers and commercially sterilized or maintained in a réfrigerated state during storage ~y the consumer.
Semi-moist or intermeaiate moisture pet foods, which - typically have a mo;sture content of a~out 20% to 50% ~y weight, were developed in order to overcome the disadvantages inherent in dry and canned pet food products. Thus, ~ecause of their increased moisture content, semi-moist products have a higher degree o pala~ility to animals than dry pet food products-. ~lso, semi-moist products are formulated to limit 1 the amount of free water available for ~acterial gro~th in the product. Such products have excellent shelf life and do not require refrigeration, ~eing preserved from bacterial attack ~y the inclusion of sufficient water solu~le material to exert a bacteriostatic effect. Typically, sugar is used for this purpose and may be present in an amount of between 15% to 35% by weight of the product. Semi-moist pet food products availa~le heretofor commonly are extruded into strands ~hich are cut to size and packaged or compressed into hamburger-like patties and packaged, and do not possess a cellular, compressible structure. Moreover, the use of high levels of sugar to-provide ~acterial stabilit~ may result in an increase in digesti~e disorders in some animals, particularly older animals.

SUMMARY OF THE I~JENT~ON
. . .
The present invention provides a highly pala~a~le, nutr;tionally balanced pet food ~aving a desirable soft moist texture. The product is characterized by an open, porous, cellular, ~read-like interior w~ich is resiliantl spongy and compressible and has a pliant, sealed surface. The soft, intermediate moisture product of this invention has excellent shelf stahility and does not require canning or refrigeration, with sta~ility against bacterial growth ~eing provided by the use of a strong solute system comprising a combination of sugar, propylene glycol, glycerine, salt and acid.
The production of a product having t~ese charac-ter-istics is accomplished by introducing a ~lend of dry ingre-dients including farinaceous materials, proteinaceous materials, sugar, salt, vitamins, minerals, and the like into tne hopper of a conventional expander or extrusion cooker )63Z
1 apparatus, from where it is conveyed into the ~arrel of the expander. ~ mix of liquid ingredients, including propylene glycol, glycerine, acid, liquified fat or oiL and water is fed into the high speed mixing cylinder located in~ermediate t~e hopper and extrusion ~arrel of the expander so that measured quantities of the liquid ingredients are thoroughly and intimately mixed with the ~lend of dry ingredients ~eing conveyed into the extrusion ~arrel. As the ingredient mix is moved progressively forward in the expander it is su~jected 1G to shear forces, mechanical work heat and pressure, with the temperature of the mix ~eing raised to above a~out 200F., prefera~ly ~etween a~out 200F. and 280F. prior to dis-charge from the expander. If desired, additional heat may ~e supplied to the expander, such as ~y passing steam around the extrusion ~arrel.
The hot, flowa~le m;x is extruded through a die .-plate having one or more die orifices, into a zone of lowerpressure, causing the extruded material to undergo expansion.

As the extrudateemerges from the die orifice, it is cut into segments of relatively uniform size which are immediately contacted with a spray of water to ranidly reduce the temp-erature of the extrudate to ~etween a~out 150~.-160F. The rapid cooling of the extruded material to this temperature promptly after it emerges from the die orifice not only stops lag-cooking of the hot product ~ut also serves to reduce moisture loss from the extrudate, and is essential in oxder to produce a product having the desired characteristics.
After contact with the water spray, the extruded material has a moisture content of about 20% to 30% ~y weight. The cooled ellets are coated with a liquified edible ~30~3Z

1 fat in an amount sufficient to provide the pellets with a total fat content of at least 7%~ The fat-coated pellets are then contacted with a liquid mix containing an antimycotic agent, a flavoring material, and water to further enhance the taste of the product and provide stability against mold gro~th.
The resulting product has a density of about 24-28 l~s. per cu. ft., a moisture content of about 20%-30% ~y weig~t, a pH o about 4.2-5.0 and an Aw of a~out 0.7~-0.86.
~ DETArL~D DE$CRIPTION OF TH~ INVENT-ION
. .
In accordance with the present invention, a mix of dry ingredients, in particulate form, is introduced into the h-opper of a conventional expander apparatus, such as a conventional Wenger expander~ T~is mix of dry ingredients includes a ~lend of farinaceous materials and proteninaceous materials capa~le of ~eing expanded into a cellular structure, one or more dry, water solu~le ~acteriostatic ingredients, ~ogether with vitamins and minerals in dry, particulate form.
The farinaceous materials which may ~e used include any of the more common grains such as corn, wheat, oats, ~arley, and the like, and their milled forms, such as corn or wheat flour, wheat germ or grits, etc. The farinaceous ingredients comprise from a~out 50~ to 60% ~y weight of the total ingredients, ~oth dry and liquid, which are fed into the expander.
The proteinaceous materials which may ~e used herein include vegeta~le protein materials such as soy~ean meal, cottonseed meal, corn gluten, etc., and proteinaceous by-products such as meat meal, ~one meal, poultry meal, andcom~inations thereof, The proteinaceous ingredients are 1 present in an amount of from about 20% to 30~ by weight of the ingredients used, with the farineaceous ingredients and proteinaceous ingredients together comprising about 75% to 85% by weight of the ingredients, ~oth liquid and dry, being extruded. In the preferred embodiment, the ratio of farinaceous ingredients to proteinaceous ingredients may ~e from about 2:1 to 3 1.
The mix of dry ingredients also includes one or more dry, water-soluhle su~stances capa~le of exerting a ~acteriostatic effect in the inis~ed product, suc~ as sugar and salt. Large amounts of sugar, commonly used in sta~ ing semi-moist pet foods, are not required. Rather, the sugar is present in an amount of a~out 5% - 7% ~y weight of the total ingredients, and salt compries ahout 0.5% - 1.5%
~y weight of the ingredients.
The required amounts of farinaceous material, proteinaceous material and ~actexiostatic material are com~ined and comminuted to the desired size Or may ~e comminuted prior to mixiny. The dry ingredients should have a particle size w~ich facilitates uniform mix;ng and cooking in later processing steps. The dry ingredîents are comminuted in any suita~le equipment, to a particle size so that they ~ill pass throug~
a 16 gauge wire mesh screen. Commonly such comminution is affected ~y grinding the dry ingredients in a hammer mill The dry ingredient mix, in particulate form, is then introduced into the hopper of a convention expander apparatus, such as a ~enger expander, from where it passes, in controlled amounts, to the ~arrel of the expander. Prefera~ly small amounts, usually less than 1% by weight, of other particulate materials such as vitamins, minerals, colours, etc., are includèd ~1~3~S32 1 in the dry ingredient mix.
A blend of liquid ingredients is mixed with the dry ingredient mix at a point prior to the dry mix entering the barrel of the expander. This liquid blend includes an acid, liquified edi~le fat or oil, one or more liquid ~acteriostatic agents and water. ~ny suita~le edible acid may ~e used, such as phosphoric, malic, citric, and the like, ~ith p~osphoric acid being preferred. The amount of acid included in the liquid blend must be sufficient to provide the finished product with a pH of ~etween a~out 4.2-5Ø

-i A small amount, ~etween a~out 0.5% - 1.5% by weight of the total ingredients, of fat or oil is included in the liquid blend. Any edible fat or oil may be used, such as soyfiean oil, cottonseed oil, tallow, etc. If the fat used i~ normally solid at room temperature it must be liquified prior to blending with the other liquid ingredients and main-tained in a liquid state prior to com~ining the liquid blend with the dry mix ingredients.

~ Bacteriostatic ag~nts, w~ich are liquid, are included ; 20 in the liquid blend in a amount of a~out 5% - 7.5% hy weight of the total ingredients. Prefera~ly propylene glycol, glycerine or a mixture of propylene glycol and glycerine is used since it not only provides sta~ility against ~acterial growth but also serves to plasticize the mix and facilitates production of a-product having a soft, spongy texture.
A small amount of water, usually a~out 1~ ~y weight of the total ingredients, is included in the liquid blend.
The ~lend of liquid ingredients is fed into the high speed mixing cylinder of the expander, located inter-mediate between the feed hopper and the extrusion barrel, for ~3~6;~

1 intimate admixing with the dry ingredient mix. The ratio of dry ingredient mix to liquid ingredient blend introduced into the extrusion barrel is controlled within the range of a~out 5:1 to 10:1, so that the admixture entering the extrusion barrel has a moisture content of about 25% to 55% by weight.
As the admixture is advanced In the expander by the screw, it is su~jected to shear forces, mechanical work, neat and pressure suficient to cook and fuse the mixture. Add-itional heat may be provided by passing steam or hot water through an annular jacket around the ~orward end o~ the extrusion barrel. The compression and supplemental ~eat are sufficient to raise the temperature of the mixture, prior to extrusion, to above about 220F., with temperatures in the range of between about 2Q0F, to 280F. usually being encountered.
The hot, flowable mixture is then forced through a die plate having a series of die orifices therethrough into a zone of lower pressure, fox example atmospheric pressure.
As the hot strands of extrudate, which have a temperature of about 180F. - 190F., emerge from the die into the zone of lower pressure, the superheated moisture contained therein partially flashes off by e~aporation to cause the extrudate to expand. In accordance with the present invention, as 500n as the extruded material emerges from the die orifices, it is cut into uniform segments of a desired length by any suitable means, such as a rotating knife positioned closely adjacent the external surface of the die plate. Immediately after cutting, the segments are contacted with a fine spray of water to reduce the temperature o~ the segments to between about 150F. - 160F., as rapidly as possible. This rapid cooling of the extruded material promptly after the material 1 is extruded is essential in order to produce a product having the desired texture, structure and density. The temperature of the extrudate should be reduced to this temperature within about 30 seconds, preferably within about 20 seconds, after extrusion. Generally, the use of water at a temperature of about 70F. - 75F., is sufficient to effect this temperature reduction. Lower temperatuxe water may, of course, be used.
The immediate cooling of the extrudate is necessary to produce the desired product, for it not only prevents over-cooking by stopping lag-cooking of the hot product, but also reduces the dissipation of moisture, in the form of steam, from the product. This enables the production of an expanded product having an open, porous, cellular structure, ~ith a moisture content of between about 20~-30% by weight. The water is applied to the extrudate at a flow rate of about 5 of the extrudate leaving the die plate. Higher flow rat~s of water are to be avoided since they result in an undesirably soft surface on thP extrudate segments.
The size and shape of the die orifices may, of course, be varied depending upon the size and shape of the product desired, and the degree of expansion to be achieved.
A die opening o about 5/16 to 3/~ inch is satisfactory.
The expanded, cooled segments may then be aero~ically packaged under ambient ~emperatures using packaging material having a low transmission of water vapor such as polyethylene, polyvinylidine chloride-coated cellophane, and the like.
Preera~1y the cooled segments are coated prior to packaging to enhance their taste, nutritional value and stability. In accordance with this pre~erred embodiment, the segments are 39 first coated with a liquified edible fat or oil, such as 1~3063~

1 soybean oil, cottonseed oil, tallow, and the like. If the fat used is normally solid at room temperature it must be liquified prior to coating onto the pellets. The fat or oil is sprayed onto the pellets in an amoun-t such that the final fat content of the pelle-ts is at least 7% by weight.
The expanded pellets preferably are also coated with a palatability enhancing solution which includes an anti-mycotic such as potassium sorbate, water, and flavoring materials such as beef digest, chicken digest, cheese flavoring and the like, including combinations of sùch flavoring materials. This solution is coated onto the pellets in any - suitable manner in proportions up to 10% solution to 90%
pellets. The amount of antimycotic contained in this solution is sufficient to provide the finished product with an antimycotic level of about 0.2 - 0.5% by weight. The resulting product is then packaged as described above.
The expanded product thus produced is a soft, expanded, mediate moisture pet food having a spongy, compressible, cellular interior with a pliant sealed surface. ~t is resistant to deterioration by bac eria, yeast and mold when stored under ordinary room temperature conditions and does not require cannin~ or refrigeration. The product has a moisture content of about 20~ - 30% by weight, preferably about 23% -28%, a density of about 24 - 2~ lbs. per cu. ft., a pH of ~etween 4.2-5.0 and a water activity of between 0.79-0.86.
The product i5 stablized against bacterial growth by control of its moisture content, water activity and pH. It is characterized by an open, porous cellular internal structure, pliant sealed surface and high degree of palatability when fed to animals.

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1 The following specific example will illustrate the process of the invention and the product produced there~y.
EX~MPLE
The following dry ingredients are mixed and blended, with the percentages being expressed as the percent ~y weight of the entire ingredient mix fed into the expander.

Ingredient Percent Oats 22.0 Whole wheat 15.0 Corn 11.3 Wheak flour lQ.0 Meat and bone meal 8. a Corn gluten 8.0 Soybean meal 5.0 Sugar 6.0 .
Salt 1.0 The mix of dry ingredients is ground through a Hammermill grinder using a 3/64 inch screen, and the ground ingredients screened over a 16 gauge wire screen. The dry ingredients are then introduced into the hopper of a Wenger - expander from where they are fed at a conkrolled rate into the expander.
A ~lend of the following liquid ingredients is prepared~ wikh the percentages expressed as percent ~y weight of the tokal product ingredient mix.

Ingredient Percent Propylene glycol 4.5 Glycerine 2.0 Phosphoric acid ~85%) 1.6 Waker 4.0 Tallow 1.0 ~ 3 ~

1 The tallow is heated to 110F. - 120F., so that it is in a liquid state when it is blended with the remaining liquid ingredients. The blend of liquid ingredients is fed into the high speed mixing cylinder of the expander, at a predetermined rate, for admixture with the dry ingredients flowing into the expander. The flo~ rate of the ingredients into the expander is controlled to provide a ratio of dry ingredients to liquid ingredients of about 7:1, with the resulting ingredient mix having a moisture content of about 25~-30% As the ingredient mix is moved through the expander, which is provided with a external steam jacket, it is su~jected to severe mechnical working and shear so that the temperature of the mix is increased to about 200F.-280F., and the mix is subjected to elevated pressure. The material is continuously passed through the expander and is extruded through triangular-shaped openings in the die plate into the atmosphere with the extrudate undergoing expansion upon passage into the atmosphere.
~ rotating knife, positioned closely adjacent the external face of the die plate, cuts the extrudate into pieces about 1/2 inch in length. A fine spray of water, having a temperaturé of about 70E'. - 75F., is appIied to the extrudate promptly after it is cut into pieces at a flow rate of about 5% by rate of the extruded product leaving the die openings, to rapidly cool the extrudate to a temperature of 150F. - 160F. Tallow, which has been heated to about 110 F. - 120 F., to liquify it, is coated onto the pieces in an amount sufficient to provide the pieces with a minimum total fat content of 7~. Upon solidification of the tallow coating, the pieces are sprayed with a hot mixture ~100F.~

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1 comprising about 78% beef digest, 10% water, 7.5% potassium sorbate and 5% cheese flavor, with the solution being applied at a rate of about 10~ by weight of the product pieces.
The thus-coated pieces are cooled and packaged.
The product thus producted has a density of 24-28 lbs.
per cu. ft. and a moisture content of 23-28%. It has a relatively soft, open, porous, cellular interior which is spongy and compressible, with a pliant, sealed surface. The proauct is highly nutritional and has excellent palatability when fed to animals, such as dogs and cats.

Claims

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

1. A method of producing a soft cellular expanded pet food product having a pliant, sealed surface and a moisture content of between about 20% - 30% by weight which consists essentially of forming a mixture of dry ingredients containing about 50% to 60% by wt. of the total ingredients of farinaceous materials, about 20% to 30% by wt. of the total ingredients of proteinaceous materials and dry, water-soluble bacteriostatic materials including about 5% to 7% by wt, of the total ingredients of sugar, the dry ingredients having a particle size such that they pass through a 16 gauge wire mesh screen, with a ratio of farinaceous materials to proteinaceous materials in said mix being about 2:1 to 3:1, forming a blend of liquid ingredients comprising sufficient edible acid to provide the product with a pH of about 4.2 - 5.0, about 0.5% to 1.5% by wt. of the total ingredients of an edible fat or oil in a liquid state, about 5% to 7% by wt. of the total ingredients of a liquid bacte-riostatic agent and water, admixing the dry ingredients mix with the blend of liquid ingredients in a ratio of about 5:1 to 10:1, passing said admixture into an expander where it is Subjected to mechanical work, shear, heat, and pressure, extruding said admixture through a die into a zone of lower pressure to cause the extrudate to expand, cutting the extrudate into particles substantially uniform in size,

Claim 1 cont.

cooling the extrudate to a temperature of about 150°F. - 160°F. within 30 seconds after extrusion through the die, coating said cooled particles with a liquified edible fat or oil to provide the particles with a fat content of at least 7% by weight, and with a solution containing an antimycotic agent, water and flavoring material, packaging said particles.
2. The method defined in claim 1 in which the dry bacteriostatic material comprises 5% - 7% sugar and 0.5% - 1.5%
salt, said amounts being expressed as percentages by weight of the total ingredient mix passed into the expander, and the farinaceous materials and proteinanceous materials together comprise about 75% to 85% by wt. of the total ingredients.
3. The method defined in claim 1 in which the dry ingredients and liquid ingredients are admixed immediately prior to introduction into the expander in a proportion sufficient to provide an admixture having a moisture content of 25% - 55%.
4. The method defined in claim 1 in which the extrudate is contacted with a fine spray of water immediately after cutting the extrudate to cool the extrudate.
5. The product produced by the process of claim 1.