Introduction

Key words: biological actIvity.food functionality.milk proteins.peptides) Milk is recognized universally as a nutritious source of high quality proteins, possessing good functional properties, primarily because of their unique amino acid composition, and many desirable physicochemical attributes.However, milk proteins can be subjected to inadvertent or deliberate proteolysis during handling, processing, and storage of dairy products.The resultant hydrolytic steps modify the physicochemical properties and functional behavior of milk proteins.Many important and significant technological implications must be considered when milk proteins undergo hydrolysis by proteinases that are naturally occurring in milk or that are of bacterial origin.For example, excessive proteolysis in milk results in the development of off-flavors and affects cheese yield.Increased amino groups resulting from proteolysis could interact with lactose and lead to Maillard or browning reactions.Another area in which the action of these proteolytic enzymes is important is the storage stability of sterilized milk products.Proteolysis is implicated in agegelation in at least some UHT-sterilized products.The presence of protein degradation products also modifies the physicochemical and functional behavior of some proteins.This area is being increasingly recognized, and fundamental understanding of the mechanisms involved is slowly evolving.