BY-PRODUCTS TECHNOLOGY

Module 5. Food application of milk protein products

Lesson 42
FOOD APPLICATION OF MILK PROTEIN PRODUCTS-2

42.1 Introduction

Milk protein products have application in beverages, desserts-type products, meat products, convenience foods, textured products and dietary, pharmaceutical and medical products.

42.2 Application in Beverages

Milk protein products are widely used in different types of beverage because of their whipping, foaming and emulsifying and nutritional properties (Table 42.1).

Table 42.1 Applications of milk protein products in beverages

42.2.1 Use of casein products

Casein products are used as stabilizers or for their whipping and foaming properties in drinking chocolate, fizzy drinks and fruit beverages. There is also a large market for sodium caseinate as an emulsifier in cream liqueurs and to a lesser extent in wine aperitifs. Cream liqueurs typically contain 16% (w/w) milk fat, 3.3% sodium caseinate, 19% added sugar and 14 % ethanol. Casein products have also been used in the wine and beer industries as fining agent, to reduce colour and astringency and to aid in clarification.

42.2.2 Use of whey protein products

Having solubility over a broad range of pH (3-8), even at their iso-electric pH, whey proteins find applications in both dairy type as well as fruit based acidic drinks. Fruit juices, soft drinks or milk-based beverages supplemented with whey protein concentrates are highly nutritious products. For use in soft drinks, defatted WPC with a low ash content, good solubility at pH 3.0 and a bland flavour is required. The WPC must also be resistant to physical deterioration or flavour changes on storage of the product and it must not mask the typical flavour of the soft drink via protein-flavour component interactions. WPCs are added to milk-like flavoured drinks to impart viscosity, body and colloidal stability and they have been included as protein supplements in powdered orange beverages and in frozen orange juice concentrates.

42.3 Application in Desserts-Type Products

Milk proteins present in dessert type products are mainly foam formers; they accelerate foaming and homogenous bubble distribution of the gaseous phase and its fixation in the liquid phase.

Table 42.2 Applications of milk protein products in dessert-type products

42.3.1 Use of casein products

Sodium caseinate is used in ice cream substitutes and frozen desserts to improve whipping properties, body and texture and to act as a stabilizer (Table 42.2). It is also used extensively in mousses, instant puddings and whipped toppings for similar reasons and also because it acts as an emulsifier and film-former.

42.3.2 Use of whey protein products

WPC has also been used in frozen juice bars and in compound coatings, especially in chocolate coatings and for frozen desserts etc.

42.4 Application in Meat Products

In the meat industry, milk proteins are used mainly in comminuted meat products rather than prime cuts; however, they are also used in injection brines for non-comminuted products like cooked hams (Table 42.3). Milk proteins have been utilized as fillers, binders and extenders in cooked comminuted meat products to reduce cook shrink and formulation cost, as well as to improve emulsifying capacity, emulsion stability, water binding, potential nutritive value and slicing characteristics. The dairy proteins can also improve or alter the consumer acceptance (flavour, mouth-feel, colour, appearance etc.) of the finished product. These proteins significantly increase the gel strength of meat proteins and it has been shown that there is a synergistic effect between milk proteins and salt soluble meat proteins, through covalent cross-linkages.

Table 42.3 Applications of milk protein products in meat products

42.4.1 Use of casein products

The main reason for growth in the use of casein in meat products lies in its functionality. Solubilised rennet caseins with high calcium levels are used in some meat products. The commonest form in which casein is incorporated in meat products is as sodium caseinate. Besides nutritional value, they are mainly used due to their excellent water binding and emulsifying properties. In comminuted meat products, a considerable amount of free fat is released during the manufacture of these products, which must be stabilized. The ability of caseinates to bind and entrap moisture through H-bonding and thereby enhancing the yield of end products has been used beneficially in various meat and sausage preparations. In addition, their salt tolerance and high protein content attract many meat traders. Caseinate thickens the gravy during frying and prevents its running out, but too much caseinate would dry up the sausage. Amongst many other functional properties, the bland flavour and neutral colour of caseinates deserve a special mention. They show no heat gelation or denaturation and have a high viscosity in solution.

Casein hydrolysates obtained by acid hydrolysis has a meat-like flavor. These are, therefore, used to accentuate the meat flavor in heat-treated canned and dried meat products such as soups. Incorporation of 3.5% protein hydrolysate gives better binding, emulsification and flavor development in fermented sausages and comminuted meat products.

Co-precipitates enhance water binding property and may prove superior to caseinate in chopped meats. The co-precipitates have good potential in various meat products such as frankfurters, sausage batter and luncheon meats as meat replacers or extenders. Sausages act as a good medium for the use of co-precipitates. The finally dispersed dairy protein matrix in sausages also can acts as a moisture binding agent, thus, developing the desirable chewy texture besides controlling shrinkage during storage and deformation while slicing. It has been found that both low and high co-precipitates improved the emulsifying capacity, emulsion stability and water holding capacity of the meat emulsion in fresh sausages at 20% replacement level.

42.4.2 Use of whey protein products

Use of denatured WPC as a meat extender in processed meat products has been found to have promising results. In frankfurters and luncheon rolls, meat protein may be replaced by whey proteins. In these systems, whey proteins are used to prepare pre-emulsions of part of the fat and to support network formation, via gelation, during subsequent cooking. Soluble, low viscosity whey protein concentrates are suitable for use in injection brines for fortification of whole meat products. Injection of fresh and cured meats with whey protein solution may increase the yield substantially.

42.5 Application in Textured Products

Milk protein-enriched products have been used in the production of textured foods (Table 42.4). Rewetted acid caseins or acidified rennet casein or co-precipitate have been mixed with carbonates or bicarbonates of alkali metals or alkali earth metals and extruded to produce puffed snack foods while caseinates have been co-extruded with wheat flour to produce protein-enriched snack-type food products.

Table 42.4 Applications of milk protein products in textured products

42.6 Application in Dietary, Pharmaceutical and Medical

Milk protein products are used extensively in dietary preparations for people, who are ill or convalescing, for malnourished children in developing countries on a therapeutic diet and for people on weight-reducing diets (Table 42.5). Milk protein hydrolysates are used for intravenous nutrition for patients suffering from intestinal disorders, protein metabolism disorders and for post-operative patients.

42.6.1 Use of casein products

Caseins are used in special preparations to enhance athletic performance and have been incorporated into formula diets for astronauts while in space. While casein products are not generally used in infant formulae, they are used extensively in specialized preparations for infants with specific nutritional problems. Caseinates, co-precipitates and milk protein concentrates are used in low-lactose formulae for lactose-intolerant infants while various types of caseinates have been used in infant foods with a specific mineral balance, e.g., low-sodium infant formulae for children with specific renal problems. Casein hydrolysates are used in specialized foods for premature infants, in formulae for infant suffering from diarrhea, gastroenteritis, galactosaemia and malabsorption. A special casein hydrolysate, low in phenylalanine, has been prepared for use in formulae for feeding infants with phenylketonuria. Casein products are also added to various foods for children and infants and to drinks as a nutritional supplement.

Table 42.5 Applications of milk protein products in dietary, pharmaceutical and medical products

Diets that are suitable for geriatrics, high-energy supplements, weight-control diets, hypoallergenic infant formulas and therapeutic or enteric diets are some of the areas in which casein hydrolysates are most useful. Casein hydrolysates are boon to people who are suffering from protein allergy or stomach disorders and to those who require easily digestible foods. The production of hydrolysed protein provides an opportunity for the dietary management of patients with various digestive disorders as a result of pancreatic malfunction, pre- and post-operative abdominal surgical patients, patients on geriatric and convalescent feeding and others who for various reasons are not able to ingest a normal diet.

Casein hydrolysates also have pharmaceutical applications in intensive care foods, anemia treatment, and prevention of blood cholesterol, treatment of dental diseases and in administration of amino acid mixture intravenously.

Specific drugs have been produced from casein; ß-casein is used as raw material for production of ß-casomorphins, tetra- to hepta peptides, which can regulate sleep, hunger or insulin secretion. Sulphonated glycopeptides prepared from casein have been used for the treatment of gastric ulcers. It is claimed that the use of casein in toothpaste prevents dental caries, in cosmetics it conceals facial wrinkles and in special therapeutic creams it heals wounds.

42.6.2 Use of whey protein products

Whey proteins are the wonder proteins for nutritional, clinical, dietetic, sports, infant foods because of their high nutritive value.

42.7 Application in Convenience Foods

Milk protein products are widely used in convenience foods, i.e. foods, which require a minimum of preparation by the consumer (Table 42.6). Milk protein products have been proposed as texture, stability and flavour enhancers in microwaveable foods.

42.7.1 Use of casein products

Whey/ caseinate blends are used as whitening agents in gravy mixes. Whey solids are used in dehydrated soup mixes and sauces to impart a milky or dairy flavour, as flavour enhancers and to provide emulsifying and stabilizing effects. Caseinates are used as emulsifying agents and viscosity controllers in canned cream soups and sauces and for the preparation of dry emulsions for use in dehydrated cream soups and sauces. In some convenience foods, caseinate-whey protein blends are used as cheap replacements for skim milk powders.

Table 42.6 Applications of milk protein products in convenience foods

42.7.2 Use of whey protein products

Whey protein products have potential as replacements for egg yolk in salad dressing. Modified whey protein-based products, with potential to replace lipids in a variety of convenience foods, have been developed.

Selected reference

Sharma, B.D., Padda, G.S. and Joshi, H.B. 1985. Uses of milk proteins in meat products - A review, Indian dairyman, 37 (11): 487-491.