BY-PRODUCTS TECHNOLOGY

Module 5. Food application of milk protein products

Lesson 41
FOOD APPLICATION OF MILK PROTEIN PRODUCTS-1

41.1 Introduction

The utilization of milk protein products as food ingredients is dependent on their physico-chemical and functional properties. Milk protein products are used for food application because of their unique properties that cannot be replaced by other proteins in certain food application. Edible casein and caseinates are long established dairy by-products finding use in many dairy and food products. Sodium caseinate has very good water binding and whipping properties and is announced by FAO and WHO as unrestricted food additive. The two main reasons for using sodium caseinate as an ingredient in foods are its functional properties and nutritive value. Industries of meat processing, baking and modified dairy products are the largest consumer of sodium caseinate. Other casein products, used in a descending order in the food industry are calcium caseinate, potassium caseinate, other caseinates and finally pure casein. One another form of casein that is commonly used in the food and pharmaceutical industry is its hydrolysates. Protein hydrolysates can be used in products depending upon the functional properties which are influenced by the raw material used; process employed; extension of hydrolysis and conditions of hydrolysis. Accordingly, protein hydrolysates can be used in foodstuffs, noodles, cheeses, bacterial assay media and as a food for persons who are allergic to milk proteins. Milk protein hydrolysates also have pharmaceutical applications.

Soluble whey protein concentrates have been found to be technically suited to a wide range of products, but its use is not cost effective in all cases. Presently, whey protein concentrates constitutes a very small proportion (10%) of protein utilization in food industry. The largest potential use of whey protein concentrates is as a replacement for non-fat dry milk (NFDM) in the food industry. Whey protein concentrates with 35% protein is perceived to be a universal substitute for NFDM, because of the similarity in gross composition and its dairy character. Superiority of whey protein concentrate over NFDM is also due to cost advantage. Whey protein concentrates of 34% protein is commonly used as a stabilizer in yogurt, bakery mixes, dietetic foods, infant foods, and confections because of its water binding, fat-like mouth-feel and gelation property. Whey protein concentrates of 50% or 80% protein offers distinct functional attributes. It is especially suited for use in nutritional drinks, soups, bakery, meat, dietary foods, and protein fortified beverages. It gives clear suspensions over a wide pH range and has a bland flavor. Some applications require undenatured ingredients to maximize water-binding capacity during food processing. It is also available in gel-forming version. During 2004-2006, number of new products produced from WPC is shown in (Fig. 41.1).

Milk protein products are used in different food products including bakery, confectionery, dairy, beverages, dietary, and meat, textured, pharmaceutical and medical application. In this lesson food applications of milk protein products in dairy, bakery, confectionery and pasta are discussed in detail.

41.2 Application in Dairy Products

Milk protein products are widely used to supplement the protein content and therefore, enhance sensory characteristics of conventionally processed dairy products and are also used in the production of a range of imitation, low fat and non fat dairy products (Table 41.1).

Table 41.1 Applications of milk protein products in dairy-type products

41.2.1 Use of casein products

Casein and co-precipitates are used in the preparation of imitation cheeses (cheese analogues), which are used in pizza, sauces, burgers, grilled sandwiches, macaroni and other dishes with a significant cost-saving compared to the use of natural cheese. The functional properties of caseins that favour their use in imitation cheese include fat and water binding, texture enhancing, melting properties, stringiness and shredding ability. Most of the edible rennet casein is used in the production of processed cheese and cheese analogues because it can significantly contribute to the structure and the functional properties of these products. In these processes, rennet casein is partially solubilised by the use of melting salts (calcium sequestering compounds) and its properties are tuned to the specific application.

Sodium caseinate is valued for its ability to emulsify fat in the production of modified dairy products such as coffee whiteners, high-fat powders, whipped cream and ice cream. Sodium caseinate is used in powdered coffee creamers, which also contain vegetable fat, a carbohydrate source and added emulsifier and stabilizers. These creamers are cheaper, have a longer shelf life and are more convenient to use than fresh coffee creams. In these products, sodium caseinate acts as an emulsifier/fat encapsulator and whitener, imparts body and flavour and promotes resistance to feathering. The use of sodium caseinate in dairy industry and in the manufacture of modified milk products has increased all around the world. The addition of 1% sodium caseinate into UHT low-fat milk fortifies this dietetic drink with protein. Soluble and dispersed high calcium co-precipitates can replace skim milk solids satisfactorily in the preparation of sterilized, flavoured low fat milk beverages. Milk products like cultured milk and UHT milk may be enriched with co-precipitates.

The addition of sodium caseinate to cultured milk products simultaneously increases the nutritive value and improves the technological quality by products. Sodium caseinate is used to increase gel firmness and reduce synersis in yoghurts, and is added to milk shakes for its emulsifying and foaming properties. In the manufacture of yoghurt, the skim milk solids may be replaced partly with the addition of soluble co-precipitates. But when the replacement is more than 30% an apparent coarseness in texture is observed in the finished yoghurt. Incorporation of hydrolysates at 5% level in cheese like foods give best results for flavor and texture.

41.2.2 Use of whey protein products

Whey protein concentrates (WPC) have been used in many different types of dairy products including various types of cheese, yogurt, ice cream, frozen yogurt, dairy spreads such as butter and low-fat butter, infant formula, cream liqueurs, creamy chocolate dairy desserts, peda and gulabjamun (Indian dairy products derived from khoa), and kulfi (a traditional frozen dairy product). Greater amount of WPC produces bigger grains in khoa, which is a desirable property for preparing kalakand - a popular khoa-based sweet. Addition of 5% WPC solids to cow milk improves the flavour, body and texture and colour of khoa. In yoghurt the viscosity and stability are improved by fortification with WPC to replace skim milk solids. Based on the emulsifying and gelling properties of whey proteins, sliceable and squeezable cheese-type products have been produced by heat treatment of skim milk and WPC solids dispersed in an emulsion of milk fat in WPC. WPC are also used in cheese filling and dips as they tend to complement cheese flavour and produce a soft end product. Whey protein hydrolysates can be used in accelerating the ripening of Domaiti cheese.

41.3 Application in Bakery Products

Milk proteins do not have properties close enough to those of wheat gluten to enable them to replace the latter protein to any great extent in bakery products; however, their use as a nutritional supplement and for functional effects in cereal-based products has considerable potential. An important functional characteristic of milk protein products in bakery applications is water binding which affects dough consistency. Bread, with milk proteins added in one form or another, shows a good crumb structure, bread yield, flavour and keeping quality. In the manufacturing of high protein biscuits, milk proteins play an important role as they increase the nutritive value and also the texture. Milk proteins are often incorporated into the base flour for pasta manufacture for the purpose of enhancing nutritional quality and to improve texture.

41.3.1 Use of casein products

One of the most important functional characteristics of casein products in bakery products is its water binding capacity. A satisfactory loaf volume can be obtained by the use of casein products. Acid and rennet casein, sodium caseinate and calcium caseinate can be used in bread making and are added at a level of 15-20% of the wheat flour. Products fortified by addition of sodium or calcium caseinate prior to extrusion include macaroni and pasta. Casein and casein derivatives are mainly used in bakery products like frozen baked cakes and cookies as an emulsifier and to improve texture, in breakfast cereals, milk biscuits and protein-enriched bread to enhance flavour and other sensory properties and also for nutritional fortification of the wheat flour (Table 41.2). The limiting amino acid in most cereal proteins is lysine and since caseins are particularly rich in lysine, they make excellent supplements for cereals. Only about 4% casein in a casein-wheat flour mixture is required to increase the lysine content by 60%. The protein efficiency ratio (PER) of wheat flour is only 1.1, compared with 2.5 for casein. By supplementing the wheat flour with casein, it is possible to increase considerably the PER of the mixture. For instance, for a 50:50 mixture of casein and wheat protein, the PER can be raised to 2.2 - 2.3. Similarly co-precipitates are also used in different bakery products.

Table 41.2 Applications of milk protein products in bakery products

41.4 Application in Confectionery and Pasta Products

Milk protein products are often incorporated into the flour base for pasta manufacture to enhance nutritional quality and also to improve texture. Products fortified by the addition of sodium or calcium caseinate, low calcium co-precipitate or WPC prior to extrusion include macaroni and pasta. Milk protein products are also used in confectionery products because of their water binding, emulsifying, whipping and browning properties.

41.4.1 Use of casein products

Caseins are used in toffee, caramel, fudge and other confections as they form a firm, resilient, chewy matrix on heating and they contribute water binding and aid emulsification. Casein hydrolysates are used as foaming agents in place of egg albumen in marshmallow and nougat as they confer stability to high cooking temperatures and good flavour and browning properties.

Casein and casein products are used in macaroni, pasta and imitation pasta products to improve texture and nutritional properties (Table 41.3). Sodium caseinate hydrolysates can be used in the preparation of noodles. Use of hydrolysates in chocolate manufacturing for increasing the protein content has also been suggested.

41.4.2 Use of whey protein products

WPCs have limited use in these products as they result in a softer coagulum and the high lactose content tends to cause crystallization during storage. However, whey proteins are very suitable for use in aerated candy mixtures and are incorporated as a frappe, which is a highly aerated sugar syrup containing the whipping protein. Replacement of egg white by WPC in the manufacture of meringues results in acceptable products only when defatted WPCs are used, while the manufacture of acceptable sponge cakes requires fat-containing rather than defatted WPCs.

Whey solids are used as an ingredient for the formulation of confectionery and pasta products to enhance the texture, flavour and colour characteristics of the finished products. It also preserves the freshness of the product in year round usage. Enrichment of pasta flours with undenatured whey protein products produces firmer cooked noodles which are also more freeze-thaw stable and suitable for microwave cooking. ‘Imitation’ or ‘synthetic’ pasta-type products containing a substantial proportion of milk protein have also been manufactured.

Table 41.3 Applications of milk protein products in confectionery and pasta products

Selected reference

De Wit, J.N. 2001. Processing of whey ingredients. In: Lecturer’s handbook on whey & whey products ed. Dr. J. N. de Wit, first edition. European Whey Products Association, Belgium: 41-72.