Enzymatic modifications are applied in many branches of the food and pharmaceutical industry. They are undoubtedly an attractive alternative for physical and chemical modifications. Many proteolytic enzymes can be used for modifying of functional properties of proteins. The differences in functional properties among proteins result from the differences in their structural properties. Enzymatic modifications affect conformation of protein molecules and, consequently, their physico-chemical properties. Enzymatic hydrolysis of proteins results mainly in the loss of their molecular weight, increase in the number of functional groups capable to ionize and exposition of hydrophobic sites. Limited proteolysis of milk proteins may improve their emulsifying and foaming properties. It is suggested that the necessary condition for advantageous emulsifying and foaming properties is amphiphacity of their structures and ensuring certain minimum molecular weight of peptides formed.