Enzymatic modification of dairy product texture

The texture of many dairy products is principally dependent on the properties and interactions of milk proteins, i.e., caseins and whey proteins, and their ability to form structures such as networks and gels when manipulated appropriately, e.g., by targeted enzymatic hydrolysis, acidification or heat-induced denaturation. The structures formed in this way lead directly to the structures associated with products such as cheese and yoghurt, as well as undesirable coagula which might occur for example heating or storage of sterilized or ultra-high-temperature (UHT)-treated milk. In addition, hydrolysis of milk proteins greatly influences dairy product structure, which may be problematic in the case of pre-processing hydrolysis of proteins by indigenous milk protease, or a positive and indeed critical role in the development of cheese texture during ripening. In recent years, significant attention has focused on new strategies for manipulating the texture of dairy products by exploiting the ability of certain enzymes to cross-link milk proteins, opening up new possibilities of manipulating the characteristics and stability of dairy products. Of these, the most well studied is probably transglutaminase, applications of which have been commercially implemented; other enzymes which have shown cross-linking activity against milk proteins include lactase, tyrosinases and peroxidases. The principal products for which these have been proposed to have benefit are yoghurt and cheese. In this chapter, the main strategies for enzymatic cross-linking of milk proteins, and consequent effects on dairy product texture, are reviewed. In addition, the significance of other enzymatic treatments, such as dephosphorylation, deglycosylation and deamidation, when applied to milk proteins is discussed, and the future perspective for enzymatic modification of dairy product texture considered.