IE42075B1 - Protein food products - Google Patents

Abstract

1492981 Coagulated milk protein drinks UNTLEVER Ltd 3 Jan 1975 [7 Jan 1974] 00674/74 Heading A2B Edible milk protein drinks containing whey protein and casein coagulated together in a higher ratio than that in naturally occuring milk may be prepared by adding undenatured whey protein to a casein dispersion e.g. milk, heating to denature the whey protein, and coagulating the casein with acid. If the casein dispersion is not milk, there must be greater than I part undenatured whey per 4 parts of casein. The whey protein may be obtained by ultrafiltration, dialysis or gel filtration. The product may contain 3-6% protein of which at least 1.5% is whey protein. The whey protein : casein ratio may be up to 1:1. The acid coagulation may be by lactic acid producing bacteria e.g. a yoghurt culture and may follow the heating step, or precede it. or the acid may be added chemically. The starting product may be skim milk or whole milk and may contain added fat. In examples cherry and orange concentrates, and strawberry jam, are included.

Description

ΊΊιιη invention relates to acid-flavoured food products, especially drinks, which ace prepared from protein especially from milk. Λ variety of milk products are manufactured by acidification of the millc to curdle the casein and other preci pi table. milk proteins and confer a desired flavour on the product. The acidification is usually effected hy lactic acid bacteria such as yoghurt micro-organisms and the milk, which may be full cream or skim milk, or mixtures thereof, or may lie reconstituted from their dried or concentrated products, is healed before and/or after acidification. An initial heating step may he applied to pasteurise the milk, thereby ensuring that where the acidification is effected bacteriologically, few other organisms are present. It also promotes the coagulability of certain milk proteins which otherwise tend to remain soluble during the acidification step.

Ifeat. treatment may additionally or alternatively be applied to the acidified product in a final pasteurisation step, with the. object of eliminating both the souring organisms and any infections that might cause spoilage. In any event, the product remains susceptible to wheying-off, aggravated by shrinkage of the curd in the product hy the heat treatment, with the expression of a proportion of aqueous fluid from the product, and a thinning-out of the body of the product.

Dense, contracted curd particles, formed dir ing the final beating, sediment rapidly and also give an undesirable granular texture to the product. The value of post-acidification heat treatment as a means of extending the shelf-life of products based on yoghurt or other acidified milk drinks is therefore severely limited, where a bulky, thickened but soft product is desired. Heat treatment at this stage may 2 0 7 5 also Ire unacceptable where live acidifying bacteria must remain in I.In· peoduct to meet loud regulations.

Water-retaining thickening agents such as edible stabilising gums, have been added to these products to retain tiie . aqueous component during and after post-acidification heat I.reatment, but again these may not be permitted and in any event tend to confer other’ undesired textural characteristics to tiie products.

It has now been Found that improved products can be obtained l>y lieating and acidifying milk or other casein dispersion, tlie.se steps lie ing carried out in either order, to effect coagulation ol' the casein protein and confer an acid flavour thereto, provided that sufficient undenatured whey protein is dispersed to increase tiie undenatured whey protein: casein ratio before the heat treatment step, the coagulated casein peoduct being stabilised against wheying-off by the rcsiil.bant denaturation ol' the whey proteins in the presence of the easi’in, before or after this is coagulated.

Preferably, milk is used as the starting material, the underiatured whey:casein ratio in milk being increased by adding undenatured whey to the milk. Where artificial casein/ whey protein mixtures are used instead of milk, the casein must be in the micellar form found in milk, and sufficient whey protein dispersed therewith to provide more than one part to four parts of casein present in the dispersion before heating, i.e. abovo the ratio found in cows' milk. a au ϊ s CQ.704 The invention applies to the preparation of all cultured or acidified milk products in addition to milk drinks, for example sour cream, flavoured sour cream dips, cheese dips and yoghurt, in which in contrast to conventional cheese products, a bulky product is required retaining a high proportion of aqueous matter. The invention is particularly applicable however to the preparation of milk drinks which have been flavoured hy acid-forming cultures, especially hy yoghurt cultures.

The coagulated products obtained hy the invention may be heat-treated for pasteurisation purposes, or left untreated so that acidifying bacteria remain alive in the product. In the latter case it is essential to adjust the undenatured whey protein:casein ratio, and then heat-treat the milk to denature the whey protein before the acidification step. ln the former case, while heat-treatment before acidification may also be carried out, for example to pasteurise the milk, the undenatured whey protein:casein adjustment must be carried out afterwards, ie after cooling, whether before or after the acidification step, and the final heat-treatment is then essential. In both cases, the essential heat-treatment must he sufficient to denature at least part of the undenatured protein in the undenatured whey present. It is preferably effected at about 90°C, hut temperatures between 70 and 150°C may he effective. Under pasteurisation conditions whey protein is usually denatured to some extent hut it is preferable in accordance with the invention to apply in the essential heat-treatment conditions in which denaturation of the whey protein is maximised. - 4 42075 Such conditions may lie rather more severe than are usually adequate for pasteurisation and for example periods of 5 seconds to 30 minutes at 75-100°C are preferred, although periods of as little as a second may be sufficient.

Suitable whey protein for the purpose of increasing the undenatured whey protein:casein ratio may he obtained for example by reverse osmosis, gel filtration and dialysis.

A proportion of denatured whey protein is acceptable in it, but its presence should be avoided as far as possible in the additive since it does not contribute to the effect of the invention. Preferably the whey has heen subjected to concentration hy at least partial, removal of water and whey powder is preferred. Liquid concentrates should preferably contain at least 5ft total undenatured protein by weight.

Without wishing to limit the scope of the invention hy the expression of any theory as to the mechanism involved, it is believed that whereas the casein content of milk provides by its coagulation a large measure of thickening in the product, resistance to wheying-off is provided by the presence of sufficient whey protein, denatured in the presence of casein. Whey protein that has been denatured in the absence of casein apparently has no stabilising function in the product. At least 1.5$ whey protein is required, at any rate in the absence of fat, which itself confers some measure of resistance to wheying-off, and in conventional products therefore, made from eg skim milk solids, in which the ratio of whey: casein protein is fixed, this corresponds to a total protein content of 6.5ft for cow’s milk products. By increasing the undenatured whey protein:casein ratio, as by using a whey source to make up part of the level nf whey protein needed to form a physically stable product, fhe level of casein can he reduced, giving a thinner final product. Moreover, whereas the protein content of milk has been supplemented in the past by the addition of whey protein in the preparation of coagulahle products, this has been hitherto already substantially denatured und therefore fails to provide a stabilising effect against wheying-off, By supplementing any undenatured whey protein that may already he present, a substantial resistance to wheying-off is provided hy the invention without an undue increase in viscosity. The source of undenatured whey protein should also be comparatively low in casein content, in order to minimise increase in viscosity in the product.

Where an unpasteurised product is required, sufficient undenatured whey protein is preferably present before heat-treatment, to give a minimum total whey protein eon tent in the product of about 1.5 wt $, to provide a product, with an adequate resistance to whey separation for practical purposes, preferably 1.5 to 3 wt $>, Where the product is pasteurised, the total protein content should be at least 4-4.5 wt $, to provide a marked degree of stabilisation against whey release, hut good results are obtained within the range 3-6$. Furthermore, if the pasteurised product is to he free from graininess then the whey protein'.casein weight ratio should preferably he at least 1:2, and especially 1:1, compared with the ratio 1:1 for natural milk, Lhe amounts being hy weigh I. undenatured whey protein and total casein. Where the product is too thick and viscous for a drink, as wil.h yoghurt, somewhat 75 higher values in concentration and ratio are preferred.

The amount of undenatured whey protein to he added io any case is to some extent a function of the amount already present in the milk. The added whey protein which is ultimately denatured, provides improved stability in products without unduly increasing their viscosity. The presence of fat or other components contributing to stability will reduce the amount of whey protein necessary.

By means of the present invention resistance to wheying-off is provided even in unpasteurised, fat-free, milk products, without producing products which are undesirably thick and viscous.

The maximum amount of undenatured whey protein that may be added in accordance with the invention is not critical. The level of casein in the final product should be at least 1.5 wt lo, preferably 1.5-350, to provide a satisfactory coagulum upon acidification. Within these 'limits, however, a wide range of products may be obtained which, according to the total milk protein content, are resistant to wheying-off.

Milk used in the preparation of the products of the invention may originate from a variety of sources. Cows' milk and the lactation products from most animals may be used, including asses', ewes', goats' milk and buffalo milk. The milk may be full cream or first skimmed, and reconstituted powdered milk which may be fortified to give a high protein milk, is also suitable.

Coagulation may be effected by culturing lactic acid bacteria or by chemically added acid. Suitable bacteria include yoghurt cultures and acidophilus bacteria generally.

Kel'I f mid koumiss- cultures may also be used. Where, the starting material is an artificial composition rather than milk, it may be necessary to ensure the presence of growth media eg sugar, in the substrate.

Chemically added acids which may be used include mineral acids and suitable organic acids.

The protein content of milk and its products, both denatured and undenatured, may be measured by use of the Prouiilk analyser marketed by Foss Electric Ltd, Hillerod, Denmark, using an amido black dye binding method. The extent of denaturation can he measured hy determining the amount of undeuatured whey protein remaining dissolved at a pH of 4.0, ut which hoth casein and denatured whey protein are coagulated. These may he removed by centrifugation from the serum containing the undeuatured whey protein.

EXAMPLE 1 A cherry-flavoured, non-fat pasteurised yoghurt drink was made from the following ingredients:Ingredient Parts hy weight Water 871.2 Skim milk powder to give 4.8 parts undenaturod whey protein + 17-4 parts caseinCO.O Whey powder to give 25 parts undetiutured whey protein Yoghurt starter in boated skim milk (giving 0.2 parts denatured whey protein + 0.8 parts casein) Sugar Cherry flavour concentrate •50 Undenatured whey protein: total casein ratio Total protein content 38.8 .0 1,000.0 60.0 .0 29-8:18.2 1. 63:1 <1.450 The ski in milk powder was dispersed in the water at 20°f! and thi' liquid heated at 90°C for 15 minutes. Upon cooling to GO°C the whey powder was dispersed in the liquid.

The mixture was then further cooled to 45°G, the yoghurt culture was added and the temperature maintained at 45°C until the pH reached 4.0. The protein curd formed hy the casein as a result of this acidification was broken up by stirring and the sugar and fruit flavour added.

The complete mix was held at 90°C for 10 minutes, homogenised at 200 atmospheres pressure, packed at 75°C, cooled and stored at 10°C. Λ similar product was prepared containing fat and incorporating more skim milk powder giving a thicker product.

IS 75 parts skim milk powder, 20.8 parts double cream, (equivalent to 10 parts milk fat), 31 parts whey powder (equivalent to 20 parts undenatured whey protein) and water to 1,000 parts, were mixed as follows: The cream was homogenised into the reconstituted skim milk powder at 150 atmospheres pressure and held at 90°C for 15 minutes. After cooling to (>0°C the whey powder was dispersed in the mixture and the preparation continued as before. The final, fruit-flavoured drink contained 4.5¾¾ protein in which the whey protein:casein ratio was 1.16:1.

Both products were free from wheying-off and remained niicrohiol ogically stable and free from granularity after storage for 3 weeks at 10°0.

In contrast, comparative tests in which the same preparative procedure was carried out, without, tho addition of niidenatured whey protein or with the addition of denatured whey pro l ein, gave products which were granular and broke down with extensive wheying-off within 24 hours.

EXAMPLE 2 An orange-flavoured, cultured pasteurised buttermilk drink was prepared using the following ingredients :- Ingredient Parts by we: Liquid milk containing 28.8 parts fat, 24 parts casein and 6.7 parts undenatured whey protein 959 10 Whey powder containing 20 parts undenatured whey protein 31 Butter culture 10 1,000 Sugar 30 Orange concentrate 30 15 Undcnaturcd whey protein:total casein ratio 1.06:1 Total protein content 4 .8% Thc milk was homogenised at 150 atmospheres pressure and C0°G to disperse its fat content, and further held at 85°C for 30 minutes. After cooling to 60°C the whey powder was dispersed in the milk and the mixture after further cooling to 30°C was inoculated with the culture and allowed to ferment at this temperature until the pH reached •1.4.

Tlie sugar and orange concentrate were added, Lhe cultured mix containing coagulated protein was stirred and healed I.o !)Οο(:, held at tliis temperature for 10 minutes, homogenised at 200 atmospheres pressure and finally packed at 7.r,°C before being stored at 10°C.

This product was pleasantly smooth to the taste and free from granularity when examined after 3 weeks' storage, showing no exudation of whey in that time. It was also free from infection by micro-organisms.

EXAMPLE 3 A series of non-fat strawberry-flavoured unpacteurised yoghurt drinks was prepared from progressively increased concentration of skim milk powder with the addition of correspondingly smaller amounts of whey protein powder, to give products of increasing viscosity but constant whey protein content at 1.75½. The skim milk powder and whey protein powder containing undenatured whey protein were dispersed in sufficient water at 20°C to form a premix making 1,000 parts by weight, less the starter culture. The premix was then heated at 90°C for 15 minutes to pasteurise the raw materials and denature the whey protein.

The mixture was cooled to 45°C, 30 parts yoghurt culture added and the temperature maintained at 45°C until the pH reached 4.0. The protein curd formed was broken up by stirring and 60 parts sugar and 120 parts strawberry jam were added. The complete mix was then cooled to 2-5°C, homogenised at 200 atmospheres and packed, all without exceeding 10°C.

No wheying-off was observed in any of these products after two weeks' storage at 5-10°C. Further particulars appear in Table 1. 2 0 7 5 TABLE 1 Parts by weight per 1000 parts premix Product Skim milk powder* Whey powder* A 75 (6) 18 (11) B 90. (7) 16 (10) C 120 (9.6) 12.7 (7.7) Protein in final product Wt $ Whry ~ratio Casein Casein Total 1.9 3.4 0.79 2.3 3.8 0.65 3.0 4.5 0.50 * Parts hy weight undenatured whey protein content in brackets.

The viscosity of these products increased substantially between the products as the level of casein was raised. For comparison, a product made from 210 parts of skim milk powder with no added whey powder, in 1000 parts of premix, giving levels of 5.2$ casein and 1.5$ whey protein in the final, strawberry-flavoured product, was also free from wheying-off for the same storage period, hut was substantially thicker to the-taste than the products in Table 1.

Claims (16)

1. CLAIMS:1. Process i’or the preparation of acid-coagulated protein drinks and other edible water-bulked products in which undenatured whey protein is added to and dispersed with casein protein in the micellar form found in milk and before or after coagulating the casein by acidification the whey is denatured in the presence of the casein by heating tlie dispersion to inhibit wheying-off, with the proviso that except where the whey is added to milk more than one part of undenatured whey is present before heating, per four parts of casein.

2. Process according to Claim 1 wherein undenatured whey protein is added to milk.

3. Process according to Claim 1 or 2 wherein the undenatured whey protein has been concentrated by ultrafiltration.

4. · Process according to any preceding claim wherein sufficient whey protein is dispersed to provide at least 1.5$ total whey protein.

5. Process according to any of the preceding claims wherein sufficient whey protein is dispersed to provide at least 4$ total protein in the product.

6. Process according to any of the preceding claims wherein sufficient whey protein is dispersed to provide 3-6$ total protein in the product.

7. Process according to any of the preceding claims wherein sufficient whey is dispersed to increase the whey protein: casein ratio to at least 1:2. 4 2 0 7 5 Κ. Process accordi iig to Cl aim 7 wherein tile sai d ratio is increased to provide about equal parts of whey protein and casein.

8. 9. Process according to any of the preceding claims wherein' sufficient casein is present to provide in the product at least L.5% casein.

9. 10. Process according to arty of the preceding claims wherein coagulation is effected by culturing lactic acid-forming bacteria.

10. 11. Process according to Claim 10 wherein the culture is a yoghurt culture.

11. 12. Process according to Claim 10 or 11 wherein tho coagulation follows the heating steps to provide a product containing live bacteria.

12. 13. Process according to any of the preceding Claims 1 to 9 wherein coagulation is effected by chemically added acid.

13. 14· Process according to any of the preceding claims in which edible fat comprises an ingredient.

14. 15. Process according to any of the preceding claims substantially as hereinbefore described with reference to the accompanying’ examples.

15.

16. Milk drinks and other water-bulked milk products whenever prepared By a process as claimed in any of tin: preceding claims.