Influence of milk peptides in determining the functionality of milk proteins: a review

Milk is a rich source of functional ingredients. Unfortunately, milk is also rich in surface-active peptides that modulate the functionality of milk proteins. Fractionation, amino acid analysis and sequencing, and computerized hydropathy calculations showed that these peptides are highly amphipathic. These peptides exert their effects primarily by markedly decreasing surface or interfacial tension and by altering the colloidal properties of proteins. The hydrophobically driven association tendency of proteins, which plays a key role in interfacial stability, is diminished because of the masking of hydrophobic patches by the peptides. Destabilization of emulsions, to an extent, may also be due to desorption of proteins from the interface as a result of the greater surface activity of amphipathic peptides. Experiments are described in which controlled hydrolysis to generate trace amounts of peptides significantly altered the functionality of milk protein powders. Some theoretical bases of the observations are discussed.