Functional Properties of Nonfat Dairy Ingredients - A Review. Modification of Products Containing Casein

Abstract

Most of the caseins, namely .alpha.S1, .alpha.S2, .beta.- and .kappa.-casein, are noted for their limited .alpha.-helix or .beta.-sheets, high proline content, varying degrees of phosphorylation, and hence, sensitivity to calcium as well as susceptibility to selective enzymatic hydrolysis. The caseins display remarkable heat stability yet are sensitive to changes in pH and ionic conditions. These properties are used to advantage for the production of casein, coprecipitates, and various types of nonfat dry milk. Casein-containing products are widely used in the food industry because of their contribution to desirable flavor and emulsifying, whipping, and hydrating properties that impart desired viscosity characteristics. Methods of modifying casein, outside the present commercial processes, are rather limited. Oxidation, reduction amidation, and succinylation can be used to impart specific functional changes but often with reduced nutritional value. Fatty acids and carbohydrate moieties also can be attached to modify surface activity and hydration properties. A variety of enzymatic methods, including dephosphorylation and proteolysis, have been proposed as means of modifying functional properties. There is an increased interest in fractionating caseins into various components to take advantage of functional properties of a specific fraction. This remains a challenge because of the unique physicochemical properties of the caseins that cause the various fractions to be highly associated.