Milk proteins constituents

Ice-cream is a product which has been developed since mechanical refrigeration became available. Ice-cream mixes comprise fats (not always dairy), milk protein, sugar and additives such as emulsifiers, stabilizers, colourings, together with extra items such as fruit, nuts, pieces of chocolate, etc., according to the particular type and flavour. The presence of this mixture of constituents means that the freezing... 

Like all fats, milk fat provides lubrication. They impart a creamy-mouth feel as opposed to a dry texture. Fat globules produce a shortening effect in cheese by keeping the protein matrix extended to give a soft texture. Milk proteins are one of the most important constituents. The primary structure of proteins consists of... 

One of the important developments in dairy technology in recent years has been the fractionation of milk into its principal constituents, e.g. lactose, milk fat fractions and milk protein products (caseins, caseinates, whey protein concentrates, whey protein isolates, mainly for use as functional proteins but more recently as nutraceuticals , i.e. proteins for specific physiological and/or nutritional functions, e.g. lactotransferrin, immunoglobulins). 

Various sugar phosphates occurring in milk are listed later under miscellaneous constituents. The glycosyl groups of several of the milk proteins are described in Chapter 3. 

Milk Proteins. Milk is a complex biological fluid that contains as the principal constituents a wide array of proteins, the milk carbohydrate (lactose), and a variety of polar and nonpolar lipids. The proteins of milk consist primarily of caseins existing as macromolecular aggregates termed casein micelles and the soluble whey or serum proteins. 

The coagulability of milk by acid or proteinases is due to certain characteristics of the milk proteins and is influenced by other milk constituents. 

By UF, it is possible to adjust the mass ratios of different milk constituents, including proteins, without adversely affecting their physicochemical properties [11]. The development of more efficient membranes in the 1990s made UF an economically and technologically feasible option to standardize milk proteins and improve the nutritional uniformity of milk and other dairy products (Figure 19.6) [31,131,132]. 

The basic constituents of milk - protein, lipid, carbohydrate - can serve as precursor substrates for the formation of a wide variety of flavor compounds. Nearly two hundred volatiles have reportedly been found in fresh and processed milk (4). Numerous research efforts have focused on the conditions and mechanisms of off-flavor development in milk. The chemical compounds responsible for these off-flavors have been characterized (3,5-7). Most fluid milk processing is carefiiUy controlled so that the appearance of caramelized and scorched flavor notes rarely occurs. The rich flavor associated with the thermal formation of diacetyl and various lactones is not objectionable to most consumers and, therefore, not a serious concern. Conversely, the sulfurous off-flavor in cooked milk is of concern and is especially prevalent in freshly processed UHT milk. 

The main constituents of this milk protein fraction have been fairly well investigated. 

Chem. Descrip. Milk protein based on fat-free milk constituents and selected carbohydrates... 

Milk consists of 85—89% water and 11—15% total soflds (Table 1) the latter comprises soflds-not-fat (SNF) and fat. Milk having a higher fat content also has higher SNF, with an increase of 0.4% SNF for each 1% fat increase. The principal components of SNF are protein, lactose, and minerals (ash). The fat content and other constituents of the milk vary with the animal species, and the composition of milk varies with feed, stage of lactation, health of the animal, location of withdrawal from the udder, and seasonal and environmental conditions. The nonfat soflds, fat soflds, and moisture relationships are well estabhshed and can be used as a basis for detecting adulteration with water (qv). Physical properties of milk are given in Table 2. 

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