GB2041717A - Expanded pet food product and method of producing same - Google Patents

Abstract

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 ingredients 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 agent, water and flavoring material. The thus coated product is then packaged.

Description

SPECIFICATION Expanded pet food product and method of producing same BACKGROUND OF THE INVENTION The present invention relates to a pet food product having enhanced palatibility and excellent storage stability. More particularly, the invention relates to a soft, intermediate moisture dog food product characterized by 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 about 10% by weight; canned products, which have a moisture content of about 70% by weight, and semi-moist or intermediate moisture products, which have a moisture content intermediate that of dry and canned products, typically between about 20%50% by weight. Whiie dry pet food products have excellent nutritional properties and superior storage and stabiliity characteristics, they suffer from the disadvantage that because of their hard, brittle texture they are generally less palatable to animals than the canned and intermediate moisture products.While canned pet food products are readily accepted by animals, such products are subject to microbiological decomposition uniess packaged in hermetically sealed containers and commercially sterilized or maintained in a refrigerated state during storage by the consumer.

Semi-moist or intermediate moisture pet foods, which typically have a moisture content of about 20% to 50% by weight, were developed in order to overcome the disadvantages inherent in dry and canned pet food products. Thus, because of their increased moisture content, semi-moist products have a higher degree of palatibility to animals than dry pet food products. Also, semi-moist products are formulated to limit the amount of free water available for bacterial growth in the product. Such products have excellent shelf life and do not require refrigeration, being preserved from bacterial attack by the inclusion of sufficient water soluble material to exert a bacteriostatic effect Typicaily, sugar is used for this purpose and may be present in an amount of between 1 5% to 35% by weight of the product.Semi-moist pet food products available heretofor commonly are extruded into strands which 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 bacterial stability may result in an increase in digestive disorders in some animals, particularly older animals.

SUMMARY OF THE INVENTION The present invention provides a highly palatable, nutritionally balanced pet food having a desirable soft moist texture. The product is characterized by an open, porous, cellular, breadlike interior which is resiliant, spongy and compressible and has a pliant, sealed surface. The soft, intermediate moisture product of this invention has excellent shelf stability and does not require canning or refrigeration, with stability against bacterial growth being provided by the use of a strong solute system comprising a combination of sugar, propylene glycol, glycerin, salt and acid.

The production of a product having these characteristics is accomplished by introducing a blend of dry ingredients including farinaceous materials, proteinaceous materials, sugar, salt, vitamins, minerals, and the like into the hopper of a conventional expander or extrusion cooker apparatus, from where it is conveyed into the barrel of the expander. A mix of liquid ingredients, including propylene glycol, glycerine, acid, liquified fat or oil and water is fed into the high speed mixing cylinder located intermediate the hopper and extrusion barrel of the expander so that measured quantities of the liquid ingredients are thoroughly and intimately mixed with the blend of dry ingredients being conveyed into the extrusion barrel.As the ingredient mix is moved progressively forward in the expander it is subjected to shear forces, mechanical work, heat and pressure, with the temperature of the mix being raised to above about 2()0OF., preferably between about 2000F. and 2800F. prior to discharge from the expander. If desired, additional heat may be suppiied to the expander, such as by passing steam around the extrusion barrel.

The hot, flowable mix is extruded through a die plate having one or more die orifices, into a zone of lower pressure, causing the extruded material to undergo expansion. As the extruate emerges from the die orifice, it is cut into segments of relatively uniform size which are immediately contacted with a spray of water to rapidly reduce the temperature of the extrudate to between about 1 500F.-1 60OF. 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 but also serves to reduce moisture loss from the extrudate, and is essential in order 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% by weight. The cooled pellets are coated with a liquified edible 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 growth.

The resulting product has a density of about 24-28 ibs. per cu. ft., a moisture content of about 20%30% by weight, a pH of about 4.2-5.0 and an Aw of about 0.79-0.86.

DETAILED DESCRIPTION OF THE INVENTION In accordance with the present invention, a mix of dry ingredients, in particulate form, is introduced into the hopper of a conventional expander apparatus, such as a conventional Wenger expander. This mix of dry ingredients includes a blend of farinaceous materials and proteinaceous materials capable of being expanded into a cellular structure, one or more dry, water soluble bacteriostatic ingredients, together with vitamins and minerals in dry, particulate form.

The farinaceous materials which may be used include any of the more common grains such as corn, wheat, oats, barley, and the like, and their milled forms, such as corn or wheat flour, wheat germ or grits, etc. The farinaceous ingredients comprise from about 50% to 60% by weight of the total ingredients, both dry and liquid, which are fed into the expander.

The proteinaceous materials which may be used herein include vegetable protein materials such as soybean meal, cottonseed meal, corn gluten, etc., and proteinaceous byproducts such as meat meal, bone meal, poultry, and combinations thereof. The proteinaceous ingredients are present in an amount of from about 20% to 30% by weight of the ingredients used, with the farinaceous ingredients and proteinaceous ingredients together comprising about 75% to 85% by weight of the ingredients, both liquid and dry, being extruded. In the preferred embodiment, the ratio of farinaceous ingredients to proteinaceous ingredients may be from about 2:1 to 3:1.

The mix of dry ingredients also includes one or more dry, water-soluble substances capable of exerting a bacteriostatic effect in the finished product, such as sugar and salt. Large amounts of sugar, commonly used in stabilizing semi-moist pet foods, are not required. Rather, the sugar is present in an amount of about 5%7% by weight of the total ingredients, and salt comprises about 0.5%-i .5% by weight of the ingredients.

The required amounts of farinaceous material, proteinaceous material and bacteriostatic material are combined and comminuted to the desired size or may be comminuted prior to mixing. The dry ingredients should have a particle size which facilitates uniform mixing and cooking in later processing steps. The dry ingredients are comminuted in any suitable equipment, to a particle size so that they will pass through a 1 6 gauge wire mesh screen. Commonly such comminution is affected by 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 Wenger expander, from where it passes, in controlled amounts, to the barrel of the expander.

Preferably small amounts, usually less than 1% by weight, of other particulate materials such as vitamins, minerals, colors, etc., are included 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 edible fat or oil, one or more liquid bacteriostatic agents and water. Any suitable edible acid may be used, such as phosphoric, malic, citric, and the like, with phosphoric acid being preferred. The amount of acid included in the liquid blend must be sufficient to provide the finished product with a pH of between about 4.2-5.0.

A small amount, between about 0.5%-i .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 soybean oil, cottonseed oil, tallow, etc. If the fat used is normally solid at room temperature it must be liquified prior to blending with the other liquid ingredients and maintained in a liquid state prior to combining the liquid blend with the dry mix ingredients.

Bacteriostatic agents, which are liquid, are included in the liquid blend in a amount of about 5%-7.5% by weight of the total ingredients.

Preferably propylene glycol, glycerine or a mixture of propylene glycol and glycerine is used since it not only provides stability against bacterial 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 about 1% by weight of the total ingredients, is included in the liquid blend.

The blend of liquid ingredients is fed into the high speed mixing cylinder of the expander, located intermediate between the feed hopper and the extrusion barrel, for 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 about 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 subjected to shear forces, mechanical work, heat and pressure sufficient to cook and fuse the mixture. Additional heat may be provided by passing steam or hot water through an annular jacket around the forward end of the extrusion barrel. The compression and supplemental heat are sufficient to raise the temperature of the mixture, prior to extrusion, to above about 220OF., with temperatures in the range of between about 2000F. to 280OF. 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, for example atmospheric pressure. As the hot strands of extrudate, which have a temperature of about 1 800F.-1 900 F., emerge from the die into the zone of lower pressure, the superheated moisture contained therein partially flashes off by evaporation to cause the extrudate to expand. In accordance with the present invention, as soon 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 of the segments to between about 1 500 F-i 600 F., as rapidly as possible. This rapid cooling of the extruded material promptly after the material 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 700F.-750F. is sufficient to effect this temperature reduction. Lower temperature water may, of course, be used. The immediate cooling of the extrudate is necessary to produce the desired product, for it not only prevents overcooking 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, with 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 rates of water are to be avoided since they result in an undesirably soft surface on the 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 of about 5/1 6 to 3/8 inch is satisfactory.

The expanded, cooled segments may then be aerobically packaged under ambient temperatures using packaging material having a low transmission of water vapor such as polyethylene, polyvinylidine chloride-coated "Cellophane" (Registered Trade Mark), and the like. Preferably the cooled segments are coated prior to packaging to enhance their taste, nutritional value and stability. In accordance with this preferred embodiment, the segments are first coated with a liquified edible fat or oil, such as 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 amount such that the final fat content of the pellets is at least 7% by weight.

The expanded pellets preferably are also coated with a palatability enhancing solution which includes an antimycotic such as potassium sorbate, water, and flavoring materials such as beef digest, chicken digest, cheese flavoring, and the like, including combinations of such 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 0.20.5% 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. It is resistant to deterioration by bacteria, yeast and mold when stored under ordinary room temperature conditions and does not require canning or refrigeration. The product has a moisture content of about 20%3% by weight, preferably about 23Y=28%, a density of about 24-28 Ibs. per cu. ft., a pH of between 4.2-5.0 and a water activity of between 0.79-0.86. The product is 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 paiatability when fed to animals.

The following specific example will illustrate the process of the invention and the product produced thereby.

EXAMPLE The following dry ingredients are mixed and blended, with the percentages being expressed as the percent by weight of the entire ingredient mix fed into the expander.

ingredient Percent Oats 22.0 Whole wheat 1 5.0 Corn 11 1.3 Wheat flour 10.0 Meat and bone meal 8.0 Corn gluten 8.G 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 \\tenter expander from where they are fed at a controlled rate into the expander.

A blend of the following liquid ingredients is prepared, with the percentages expressed as percent by weight of the total product ingredient mix.

Ingredient Percent Propylene glycol 4.5 Glycerine 2.0 Phosphoric acid 185%) 1.6 Water 4.0 Tallow 1.0 The tallow is heated to 11 00F.-1 200F., 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 flow 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 subjected to severe mechanical working and shear so that the temperature of the mix is increased to about 2000F.-2800F., 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.

A rotating knife, positioned closely adjacent the external face of the die plate, cuts the extrudate into pieces about 1/2 inch in length. Afine spray of water, having a temperature of about 700F.-750F., is applied 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 1 500F.-1 600 F. Tallow, which has been heated to about 11 00F.-1 200 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 (100OF.) 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 produced has a density of 24--28 Ibs. per cu. ft. and a moisture content of 2328%. It has a relatively soft, open, porous, cellular interior which is spongy and compressible, with a pliant, sealed surface. The product is highly nutritional and has excellent palatability when fed to animals, such as dogs and cats.

Claims (5)

1. A method of producing a soft cellular expanded pet food product having a moisture content of between about 20%30% by weight which comprises forming a mixture of dry ingredients containing farinaceous materials, proteinaceous materials and dry, watersoluble bacteriostatic materials, the dry ingredients having a particle size such that they pass through a 1 6 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, an edible fat or oil in a liquid state, a liquid bacteriostatic 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, contacting the particles with a water spray to rapidly cool the particles to a temperature of 150aF.--1 600F.

coating said cooled particles with a liquified edible fat or oil to provide the 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 anti-mycotic agent, water and flavouring material.

packaging said particles.

2. The method defined in claim 1 in which the farinaceous materials in the dry mix comprise 509#60% by weight, the proteinaceous materials comprise 209#30% by weight and the dry bacteriostatic comprises 5%7% sugar and 0.59#1 .5% salt, said amounts being expressed as percentages by weight of the total ingredient mix passed into the expander.

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 cooled to a temperature of 1 500F.-1 600 F. within 30 seconds after extrusion through said die.

5. The product produced by the process of claim 1.