IES970932A2 - A process and apparatus for preparing a mouldable dog food - Google Patents

Abstract

The present invention relates to a process and apparatus for producing a mouldable dog food, said process involving the preparation of a food premixture from a nutritionally balanced mixture of protein, carboydrate, fat, vitamins and minerals and sufficient water to bring the water content within the range 5 to 20%. Said process also eliminates the need to use gelatin and incorporates a pH adjusting agent which prevents process problems caused by high acidity. The aforementioned premixture is fed as a mixed food paste to a die by a screw system with or without added water, wherein it is fully cooked at approximately 100°C to gelatinise all starches present. The finally extruded product is an easily digestible, nutritious, stable food piece which is cohesive and maintains its shape. <Fig.1>

Description

A Process and Apparatus for Preparing a Mouldable Dog Food11 Introduction The present invention relates to a dog food and in particular to a process and apparatus for making such a mouldable dog food.

There are considerable advantages in preparing a dog food by extrusion and injection moulding. For example, typically an extrusion and injection moulding process comprises preparing a premix having a heat sensitive binding agent and gelatin, delivering the premix to a feed screw, subsequently injecting the mix into a mould and then moulding the product. For example U.K. Patent Specification No. 2 179 589 discloses such an extrusion process where the barrel is cooled and the heat sensitive binding agent remains substantially inactivated and is only activated either on injection or in the mould.

Indeed many food extrusion processes are well known and it has been appreciated for some time that there is a need for a mouldable food product, which is relatively hard such that a dog, for example, can chew it. It is known to provide all sorts of indigestible materials for dogs to chew, even plastics materials. Unfortunately while dogs may enjoy chewing these relatively indigestible products, they are not necessarily good for the dog.

European Patent Specification No. 0 562 193 describes one particular dog food that it is claimed can be extruded and moulded successfully. This dog food it is claimed is of a modifiable hardness and comprises a homogenous mixture of casein and gelatin having a total moisture content of 10-15% and sealed within moisture-proof packaging such that upon removal from the said package and upon exposure 5970932 - 2 to heat the dog chew may be caused to expand and decrease in hardness. The particular novel feature claimed for this invention is that the dog chew additionally comprises poultry meal and said homogenous mixture comprises 1571.25% poultry meal, 15-71.25% casein and 5-40% gelatin, the combination of the poultry meal and casein amounting to 60-95%. The specification further goes on to explain that in order to cause the ingredients to be intimately combined with one another, the mixture is heated to the components' melting temperatures under pressure and the mixture's moisture content is adjusted by either heating to drive off excess moisture or steam injection to increase the moisture, at which time the material is either extruded or it is suggested preferably moulded into pre-selected shapes. It is also suggested that a standard injection moulding machine is the preferred method for producing the chews.

It is already well known, for example from WO-A-91/16825, for a high protein meal of animal origin to be added as a filler to a casein-gelatin combination and this European Patent No. 0 562 193 suggests that the use of poultry meal is particularly advantageous in that the dog food does not dry out as quickly, as would be expected, and it has an exceedingly extended shelf-life.

U.S. Patent Specification No. 5,480,673 describes a relatively complex way of providing an extruded cooked product while maintaining a high level of desirable soluble protein.

U.S. Patent Specification No. 4,251,556 describes a pet food in which a caseinate binder is partially replaced by a vegetable protein and an amylaceous material.

S®70932 - 3 U.S. Patent Specification No. 4,127,678 describes another way of replacing sodium caseinate again using a vegetable protein.

However, there are still problems in extruding and forming such products and unfortunately the ingredients described in this European Patent Specification No. 0 562 193 are relatively expensive.

The present applicants have found that preferably gelatin should not be used and further it is preferable to alter the pH of the material in the mixture if successful binding is to occur. This is also particularly the case when gelatin is omitted from the mixture. It has long been realised that starches on the application of heat can be gelatinised, but the problem then is they are very difficult to handle in the extruder and in the mould. Further it is known that the solubility properties of casein and its salts are poor in acidic environments, and that the pH should be altered to fall within the range of 6.0 - 8.0 in order to achieve a good degree of mixing. Further it becomes advantageous to alter the pH of the material, in particular where the water activity is above approximately 0.85. Reducing the pH value improves the stability of the food composition where this water activity is high, however a balance must be struck between stability and acceptable pH values for consumption. Indeed it is further known that acidic foods increase plaque and accelerates tooth decay and thus while many of the food products produced for dogs appear of their nature to be suitable, they are in fact too acidic and thus cause increased tooth decay.

A further problem that has become apparent in the moulding of these products is to ensure that there is no clogging within the screw and the basic raw ingredients, when - 4 5970932 mixed, can be handled in the extruder and can be successfully injected into the mould. Thus, there is a need for producing a product that can be gelatinised without the addition of gelatin and at the same time can be handled in the extruder in such a way as not to cause the build up of materials within the extruder and further to ensure that the premix is adequately mixed and handled within the extruder so as to provide a coherent and cohesive product.

The present invention is directed towards providing a mouldable dog food ingredient and thus a dog food that can be relatively easily handled within an extruder and moulding machine, that incorporates a pH adjusting step which solves the problems caused by high acidity, will not use added gelatin and finally can be efficiently handled within the extruder and mould.

Statements of Invention According to the invention there is provided a process for preparing a dog food by extrusion and injection moulding comprising the steps of: preparing a premix as described above; delivering the premix to the feed screw; heating the mix in a feed screw to fully cook and gelatinise the starch and form a liquid; injecting the liquid under pressure into a mould; simultaneously cooling the mould; and ejecting the moulded product from the mould. - 5 £•70932 Preferably the heating is carried out within the range 75 to 125°C, most preferably in the range 95 to 105°C.

In one embodiment of the invention the mixture is progressively pressurised along the screw.

Preferably the liquid is ejected at a pressure of between 500,000 kp/cm2 to 1,600,000 kp/cm2, most preferably the liquid is ejected at a pressure of between 600,000 kp/cm2 to 1,000,000 kp/cm2.

Further the invention provides a moulding apparatus for producing a dog food from the ingredients given above, the moulding apparatus comprising: a cooking and feed barrel; a food ingredient hopper adjacent one end of the feed barrel forming a feed inlet; an injection nozzle at the other end of the barrel; a mould fed from the injector nozzle; a heater surrounding the barrel between the food ingredient hopper and the injector nozzle; a mould cooler; and a feed screw mounted in the barrel and having an associated check ring adjacent the injector nozzle in which the route diameter of the screw increases adjacent the check ring for smooth transition of ingredient across the check ring to the injector nozzle. - 6 S9 7 0 9 3 2 The particular advantages here are by heating the mix in the screw and fully cooking, the material is gelatined. There is no question of the product not being homogenous, not being fully cooked and not being easily injectable. Cooling in the mould ensures that when the liquid enters the mould, the liquid as it solidifies under the injection moulding process also shrinks away from the mould walls.

In one embodiment of the invention the screw has a thread the leading face of which is substantially perpendicular to the longitudinal axis of the screw and a trailing face which forms a smooth inclined transition from the root of the thread to its outer tip.

Preferably the mean angle between the trailing face and the screw axis is between 30° and 60°, most preferably the angle is between 40° and 50°.

In an embodiment of the invention the root diameter of the screw increases from feed inlet to the injector nozzle.

In another embodiment of the invention the pitch of the thread decreases from feed inlet to injector nozzle.

Preferably the mould surface area to mould volume is in the ratio 1.5:1 or more preferably in the ratio 3:1.

It has been found with the present invention that one of the principal matters that requires addressing if desirably some of the more desirable constituents are to be used in the food ingredient mix or premix that there is a need to ensure that there is a smooth transition of ingredient across the check ring to the injector nozzle and this can only be achieved by redesigning the screw to adequately handle such materials. By having a leading S9 7 0 9 3 2 - Ί face which is substantially horizontal as is conventionally the case, the actual pushing of the ingredient through the screw is achieved as in other extruders, while by having a gradual trailing face, the product is relatively easily forced up the screw. Increasing the root diameter and or decreasing the pitch of the thread ensures that as the product progresses up the extruder it is continually compressed. The choice of mould surface as against total mould volume is critical since the less volume there is relative to the mould surface the easier it is to ensure that adequate shrinking of the product taking place within the mould when the mould is cooled.

In the moulding apparatus the screw preferably terminates in a conical head adjacent the injector nozzle, having a plurality of axially arranged slots in its conical surface to facilitate passage of ingredient from the screw to the mould.

Passage of ingredient into the mould without sticking is vital.

Detailed Description of the Invention The invention will be more clearly understood from the following description of some embodiments thereof given by way of example only with reference to the accompanying drawings in which:Fig. 1 is an outline drawing showing an injection moulding apparatus according to the invention, Fig. 2 is a side view of an outline of portion of the mould and barrel housing a feed screw according to the invention, 5970932 Fig. 3 is a side view of a screw, Fig. 4 is a typical section through part of the screw, and Fig. 5 is a sectional view in the direction of the arrows V-V of Fig. 4.

Referring to Fig. 1 there is provided a moulding apparatus indicated generally by the reference numeral 1 comprising a cooking and feed barrel not shown on this drawing housed within heating bands 2 a food hopper 3 adjacent one end of the feed barrel forming a feed inlet, an injector nozzle 4 at the other end of the feed barrel 2, a mould indicated generally by the reference numeral 5 comprising a fixed platen 6 and a moving platen 7 operated by a locking cylinder 8. An injection cylinder 9 is also provided. All this in general outline is conventional.

Referring now specifically to Fig. 2, it will be noted that each mould platen 6 and 7 is provided with cold water chambers 10 and 11 respectively fed by cold water feed and return pipes 12 and 13 respectively.

Referring now specifically to Figs. 2 to 5 there is illustrated a screw indicted generally by the reference numeral 20 mounted within a feed barrel 30. The screw 20 has a conical head 21 and check ring 22 and threads 23. Three axially arranged slots 24 are formed in the conical head 21. The root diameter is identified by the reference letters DI and D2 and it will be noted that the root diameter increases gradually from the back or entrance of the feed screw 20 towards the head 21 and further the pitch of the screw identified by the letters Pt and P2 decreases in the same direction. Further it will be noted 9 3 2. - 9 that there is a smooth transition between the last thread and the check ring 22 at 23.

Referring now specifically to Fig. 4 it will be noted that each thread 23 has a leading face 25 which is substantially perpendicular to the longitudinal axis of the screw and a trailing face 26 which forms a smooth inclined surface between the root of the thread identified by the reference numeral 27 and its tip 28. This smooth transition surface subtends a mean angle a in this embodiment of approximately 45° between the screw axis. This angle can be anything from between 30 and 60°, but ideally is between 40° and 50°.

It is envisaged that the mould surface area shall generally speaking be large relative to the mould volume and ideally is in the ratio 3:1. Preferably it is in the range 1.5:1.

In operation a premix as will be described hereinafter is formulated and tested sufficiently to find the approximate water content when cooked. Then sufficient water is added to the ingredient to ensure that the total water content of the ingredient namely the actual water added and the water that will be released during the cooking process is within the range 15 to 20% by weight. The ingredient is then placed in the feed hopper and delivered to the feed screw where it is heated to approximately 100° to fully cook and gelatinise the food ingredient as it progresses down the feed screw. The temperature generally is of around 100°, but may vary depending on the ingredients to between 75° to 125°C, but is more often within the range 95° to 105°C. As the ingredient mixture moves along the feed screw, it is progressively pressurised until all the starches have been gelatinised and the mixture totally cooked, when it forms a liquid which is then injected at - 10 a pressure of between 500,000 kp/cm‘ to 1,600,000 kp/cnr and preferably within the range 600,000 kp/cm2 to 1,000,000 kp/cm2 into the mould. The mould which is cold ensures that as the mixture expands into the mould, it also hits a relatively cold mould surface where the product shrinks slightly thus making the product much easier to eject after moulding.

The examples which follow give some samples of the range of ingredients used and some preferred mixes. While the mixes are given as a mouldable dog food ingredient, it will be appreciated that the final product will also have the same ingredient in the same respective ratios by weight, but the final percent of the weight of the total food product will depend on the cooking process and the amount of water evaporated, during the moulding.

TABLE 1 RANGE OF DOG FOOD INGREDIENTS - SOLIDS - 30% weight by weight Protein 35 - 84% weight by weight Starches 0 - 10% weight by weight Fat 0 - 5% weight by weight Glycol 3% weight by weight additives (including vitamins) - 5% weight by weight Ph Adjusting Agent - 10% (including glycol) weight by weight Flavourings % weight by weight Phosphates 5970932 - 11 Ο - 5% weight by weight preservatives - 20% weight by weight Water.

TABLE 2 PROTEIN Meat Digest Casein. - 12 TABLE 3 STARCHES Sugar Beet Tapioca Corn Broken rice Wheat flour Potato Rice flour Corn flour Oat flour.

TABLE 4 PRESERVATIVES Potassium sorbate Sodium priopionate Sodium chloride Sorbic acid Propylene glycol.

TABLE 5 PHOSPHATES Monobasic sodium phosphate Monocalcium phosphate Sodium Tripolyphosphate Calcium phosphate Sodium Glycerophosphate Sodium biphosphate . - 13 TABLE 6 FLAVOURINGS Monosodium glutamate Sodium chloride Meat digest Cheese Powder Chocolate Chlorophyll Honey Vegetable.

TABLE 7 FATS Corn oil Fish oil Animal fat Edible oil generally Wheat germ oil.

TABLE 8 ADDITIVES Choline chloride Absorbic acid Vitamin mix Potassium chloride.

TABLE 9 pH ADJUSTING AGENT Calcium carbonate S 17 0 9 3 2 - 14 The following table gives details of three specific mixes.

TABLE 10 MIXES Mix 1 Mix 2 Mix 3 Water 7% 8.1% 6% PROTEIN Meat Digest 5% 2.0% 3% Sodium Caseinate 16% 22% 20% STARCHES Potato 16.25% 15% Rice Flour 13% 9% 12% Tapioca 13.5% 9.6% 19.5% 10 Broken Rice 10% 31% 7% PRESERVATIVES Potassium Sorbate 0.5% 0.3% 0.5% Potassium Propionate 0.25% 0.3% 0.75% Sodium Chloride 2% — Propylene Glycol 2.5% 3.6% 3.0% 15 PHOSPHATES Sodium Tripolyphosphate 0.5% 1.6% 1.0% Calcium Phosphate 0.25% 2.6% 1.05% Sodium Glycerophosphate 0.25% 0.5% Sodium Biphosphate 0.5% - FLAVOURINGS Monosodium Glutamate 3% 3.0% 20 FATS Corn Oil - 3.1% — Animal Fat 1% — ADDITIVES Bran -- 2% 1.0% Choline Chloride 0.5% 0.8% Vitamin Premix 0.5% 0.6% 0.7% 25 Absorbic Acid 1.5% 1.2% Potassium Chloride — 1.6% pH ADJUSTING AGENT Calcium Carbonate 3% 2.6% 4.0% 5970932

Claims (5)

1. A process for preparing a dog food by extrusion and injection moulding comprising the steps of: preparing a premix containing: 35% - 84% w/w Starches 15% - 25% w/w Casein 0% - 40% w/w Fat, glycol, flavourings, additives meat digests, phosphate and vitamins and sufficient water to bring the water content of the ingredient.

2. A process for preparing a dog food by extrusion and injection moulding substantially as described herein.

3. A moulding apparatus for carrying out the process of claim 1 or 2 comprising: a cooking and feed barrel; a food ingredient hopper adjacent one end of the feed barrel forming a feed inlet; an injection nozzle at the other end of the barrel; a mould fed from the injector nozzle; a heater surrounding the barrel between the food ingredient hopper and the injector nozzle; a mould cooler; and - 16 5970932 a feed screw mounted in the barrel and having an associated check ring adjacent the injector nozzle in which the route diameter of the screw increases adjacent the check ring for smooth 5 transition of ingredient across the check ring to the injector nozzle.

4. A moulding apparatus as claimed in claim 3 in which the screw has a thread the leading face of which is 10 substantially perpendicular to the longitudinal axis of the screw and a trailing face which forms a smooth inclined transition from the root of the thread to its outer tip and in which the mean angle between the trailing face and the screw axis is between 30° and 15 60° and in which the root diameter of the screw increases from feed inlet to the injector nozzle while the pitch of the thread decreases from feed inlet to injector nozzle.

5. A moulding apparatus for carrying out the process of 20 claims 1 or 2 substantially as described herein with reference to and as illustrated in the accompanying drawings.