GB2031259A - Milk substitute - Google Patents

Abstract

A milk substitute in the form of an unreconstituted powder, containing more than 10% casein, is given an extended storage life following reconstitution by the presence of a pH-responsive preservative, such as propionate, and an edible acidifying system, for example one containing glucono delta lactone, which will gradually within a few hours following reconstitution reduce the pH of the milk substitute to a value in the range 6.2 to 5.2.

Description

SPECIFICATION Milk substitutes The present invention relates to milk substitutes in powder form which when mixed with an appropriate quantity of water provide a milk-like liquid suitable for feeding to young mammalian animals such as calves, lambs and piglets.

Conventional milk substitutes are generally based on skimmed milk powder and fat, fortified with added minerals, vitamins, growth pro motor and other minor ingredients. Whey powder, and non-milk proteins such as soya protein, can be included. These conventional milk substitutes have excellent nutritional properties, but in practice suffer from the defect that following reconstitution with water they acidify through bacterial action and this leads to undesirable coagulation. The maximum time that such a milk substitute can be left unconsumed after reconstitution during the summer is 36 hours, and if a residue of this unconsumed material is allowed to remain in a storage vessel which is topped up with freshly reconstituted milk substitute, the mixture will be unusable within a further 24 hours.

In farming situations this problem of spoilage increases labour costs because the stockman must clean out his storage vessels and replenish them with freshly reconstituted milk substitute on a daily basis, in order to ensure that his animals are receiving uncoagulated feed. The consequences of not maintaining such a strict regime are poor feed intakes and poor feed conversions, and a constant risk of serious gastrointestinal infections (scouring) which can further retard growth or even lead to death. Further, coagulation of the feed can cause blockage of teats and other feeding mechanisms. Also, the unattractive appearance of the coagulated feed may cause the careful stockman to discard the feed prematurely even though bacteriologically it could still be fed safely to the animals.

A recent development has been the marketing of milk substitutes which incorporate mixtures of edible organic acids and salts of such acids which appear to impart longer storage life after reconstitution. These acidified milk substitutes are all based principally on whey powder, and contain only minor amounts of skimmed milk powder or caseinates.

Clearly it would be beneficial to enhance similarly the storage life of milk substitutes that contain substantial amounts of milk powder or caseinates. Advantage could thus be taken of the ready availability of skimmed milk powder, of which there is currently an embarassing surplus.

However, the addition of acids to milk substitutes containing milk powder could cause immediate coagulation of casein on reconstitution.

Coagulation of casein is known to occur at pH 4.7 and below, but even where the nominal pH of the reconstituted product is higher than 4.7 it is possible that localised concentrations of high acidity could occur during reconstitution, leading to the development of curds. In the formulation of an acidified milk substitute containing substantial amounts of casein it is essential therefore to ensure that the occurence of any such local concentrations is minimised.

The invention provides a milk substitute in the form of an unreconstituted powder containing, by weight, more than 1 0% casein, and acidresponsive edible preservative, and an edible acidifying system which will gradually within a few hours reduce the pH of the milk substitute to a value in the range 6.2 to 5.2, preferably not lower than 5.5, after the milk substitutes has been reconstituted.

A further embodiment of the invention is a method of rearing young mammalian animals, such as calves, wherein the animals are provided on an individual or group basis with a quantity of liquid feed reconstituted from a milk substitute oF the invention, the liquid feed being presented in a manner such that the animals can drink ad lib thereof and the quantity being sufficient to sustain the animals for a period of more than 36 hours, preferably from 3 to 4 days.

By an acid-responsive preservative we mean a preservative the effectiveness of which increases as pH decreases. Preferred preservatives are water-soluble propionates, ideally as sodium or calcium salts. Acetates and formates represent alternatives. Preferably the preservative comprises at least 0.5% and ideally at least 1%, by weight of the milk substitute. In general, the preservative will not comprise more than 5%, and typically not more than 3% by weight of the milk substitute.

Mixtures of two or more preservatives can be used if desired, the above percentages then being taken as indicating the total preservative content of the milk substitute.

The acidifying system must include at least one constituent which, on admixture with water, releases acidity slowly rather than immediately.

A preferred embodiment of the invention is the use of an acidifying compound, such as a lactone, which is readily soluble in water but which gradually hydrolyses to an organic acid once in solution. A preferred example of such a compound is glucono delta lactone.

The acidifying system can comprise solely one or more compounds which release their acidity slowly, or in addition it can include one or more other compounds which are both readily watersoluble and which release all of their acidity immediately on being dissolved in water. One embodiment of the acidifying system of the invention is one or more rapidly water-soluble edible organic acids, such as citric acid, malic acid ortartaric acid, in combination with one or more compounds which release their acidity slowly, the former being present in the milk substitute in an amount sufficient to lower the pH of the reconstituted milk substitute rapidly to a value in the range 6.2 to 5.8 and the latter being present in an amount sufficient to maintain that reduced pH or gradually to lower the pH further to a value in the required range of 6.2 to 5.2.

The total amount of slowly-acidifying compounds present in the milk substitute should be at least 0.1% by weight, and preferably at least 0.2% by weight. Preferably the upper level does not exceed 5% by weight. Where the acidifying system comprises slowly-acidifying compounds and rapidly-acidifying compounds, the total level of the slowly-acidifying compounds will generally not exceed 1% by weight of the milk substitute.

The total level of the rapidly-acidifying compounds present will be determined by the relative acid strength of the compounds chosen, and the contribution to the pH drop that they are intended to provide. Typically the total level of such rapidlyacidifying compounds present will not exceed 2% by weight of the milk substitute.

In addition to the acid-responsive edible preservative and the edible acidifying system, a milk substitute in accordance with the invention can contain any of the standard ingredients used in conventional milk substitutes. Typically these are 50 to 80% skimmed milk powder, 10 to 25% fat, O to 30% of spray-dried whey powder and/or nonmilk proteins such as soya protein, fish meal, single-cell protein and legume meal, and a total of up to 10% minerals, vitamins and other minor additives.

All percentages given throughout this specification are expressed by weight of the milk substitute in the form of an unreconstituted powder because this is the physical form in which milk substitutes are sold commercially.

Reconstitution of the milk substitute into a drinkable product for feeding to mammalian young will entail mixing the dry powder with an appropriate quantity of water in the conventional manner. As a precaution against casein coagulation, it is sensible to avoid the use of hot water in the reconstitution of the milk substitute, and therefore water at a temperature below 500C is recommended. Cold water can be used.

Typically, the quantity of the dry powder used will be 80 to 200 g per litre of water.

Manufacture of a milk substitute of the invention can be accomplished by simply dry mixing of the individual ingredients. Alternatively, the ingredients can be added to liquid milk prior to the conventional spray-drying of such milk to yield milk powder.

The invention is illustrated by the following Examples.

EXAMPLE 1 A calf milk substitute, based on fat-filled skimmed milk powder, was prepared by dry mixing and contained, by weight, 1 5.5% casein, 6.1% whey protein, 45% lactose, 16.7% fat, 2.37% sodium propionate, 2.84% glucono delta lactone, 0.05% "Payzone" (a commerciallyavailable growth promoting additive containing by weight thereof 5% nitrovin, which may have some beneficial enhancing effect on the preservation system of invention) and sundry conventional minerals, vitamins and moisture. The milk substitute was reconstituted in tap water at 400 C, at a level of 100 g per litre of water. After thorough mixing, the reconstituted product had a normal un-coagulated milk-like appearance. By the time the reconstituted product had cooled to ambient temperature (about 200C) its pH was 6.04.After standing at ambient temperature over the weekend, the pH had dropped to 5.85. After a total of 4 days the pH was 5.21. Throughout the 4 days the reconstituted product remained un coagulated and had a fresh milk-like smell.

COMPARATIVE EXAMPLE In contrast, a milk substitute of essentially similar formulation but containing no sodium propionate or lactone, reconstituted in exactly the same manner and at the same time, curdled during the weekend and had the appearance and smell of a product obviously spoiled by microbiological activity.

EXAMPLE 2 A calf milk substitute of formulation similar to that of Example 1 , but containing, by weight, 2.5% sodium propionate and 2.8% glucono delta lactone, was reconstituted in tap water at 40 C at a level of 1 00g dry powder per litre of water. The reconstituted product was still unspoiled after three days at ambient temperature ( 8--200 C).

Claims (21)

1. A milk substitute in the form of an unreconstituted powder, containing by weight more than 10% casein, an acid responsive edible preservative and an edible acidifying system which system will gradually within a few hours reduce the pH of the milk substitute to a value in the range 6.2 to 5.2 after the milk substitute has been reconstituted.

2. A milk substitute according to claim 1, wherein the edible acidifying system will gradually within a few hours reduce the pH of the milk substitute to a value not lower that 5.5 after the milk substitute has been reconstituted.

3. A milk substitute according to claim 1 or claim 2, wherein the preservative is a watersoluble propionate.

4. A milk substitute according to claim 3, wherein the propionate is present as its sodium or calcium salt.

5. A milk substitute according to any one of the preceding claims, wherein the total preservative content of the milk substitute is at least 0.5% by weight

6. A milk substitute according to claim 5, wherein the total preservative content is at least 1% by weight.

7. A milk substitute according to any one of the preceding claims, wherein the total preservative content is not more than 5% by weight.

8. A milk substitute according to claim 7, wherein the total preservative content is not more than 3% by weight.

9. A milk substitute according to any one of the preceding claims, wherein the acidifying system comprises at least one compound which is readily soluble in water but which gradually hydrolyses to an organic acid once in solution.

10. A milk substitute according to claim 9, wherein the gradually hydrolysing compound is a lactone.

11. A milk substitute according to claim 10, wherein the lactone is glucono delta lactone.

12. A milk substitute according to any one of claims 8 to 10, wherein in addition the acidifying system includes one or more compounds which are readily water-soluble and which release all their acidity immediately on being dissolved in water.

13. A milk substitute according to claim 12, wherein the readily water-soluble component of the acidifying system includes citric acid, malic acid or tartaric acid.

14. A milk substitute according to claim 12 or claim 13, wherein the rapidly acidifying component of the acidifying system is present in the milk substitute in an amount sufficient to lower the pH of the reconstituted milk substitute rapidly to a value in the range 6.2 to 5.8, and the slowly acidifying component is present in an amount sufficient to maintain that reduced pH or gradually to lower the pH further to a value in the range 6.2 to 5.2.

1 5. A milk substitute according to any one of the preceding claims, wherein the total amount of slowly acidifying compounds present is at least 0.1% by weight.

1 6. A milk substitute according to claim 1 5, wherein the total amount of slowly acidifying compounds is at least 0.2% by weight.

1 7. A milk substitute according to any one of the preceding claims, wherein the total amount of slowly acidifying compound present does not exceed 5% by weight.

18. A milk substitute according to any one of the preceding claims, which contains 50 to 80% skimmed milk powder, 10 to 25% fat, 0 to 30% of spray-dried whey powder and/or non-milk proteins, and a total of up to 10% minerals, vitamins and other minor additives.

19. A milk substitute according to claim 1 and substantiaily as hereinbefore described in Example 1 or Example 2.

20. A method of rearing young mammalian animals, such as calves, wherein the animals are provided on an individual or group basis with a quantity of liquid feed reconstituted from a milk substitute according to any one of the preceding claims, the liquid feed being presented in a manner such that the animals can drink ad lib thereof and the quantity being sufficient to sustain the animals for a period of more than 36 hours.

21. A method according to claim 20, wherein the quantity is sufficient to sustain each animal involved for a period of 3 to 4 days.