Bioactive proteins and their physiological functions in milk.

Milk is the basic food for infants and newborn animals, providing a rich source of proteins, carbohydrates, minerals, and vitamins. Milk also provides nourishment for people of all ages due to its abundant nutrients, and it is used in the manufacture of numerous health-related products. Milk contains caseins and whey proteins as the two major protein classes. Caseins fall into four major types known as alpha s1-, alpha s2-, beta- and kappa-casein, whereas whey proteins comprise a mixture of globular proteins including ss-lactoglobulin, alpha-lactalbumin, serum albumin, lactoferrin, and other bioactivators. The various biological activities of these proteins are involved in preventing and treating numerous nutritional, physiological and metabolic diseases. This article reviews the bioactivities and functions of milk proteins, which may shed light on future application of milk bioactive substances.