Preparation and characterization of whey protein hydrolysates: applications in industrial whey bioconversion processes.

A whey protein hydrolysate was prepared by incubation of reconstituted whey or a whey protein concentrate with Alcalase 0.6L. The proteolytic degradation of alpha-lactalbumin and beta-lactoglobulin initially resulted in 6-kDa and, later, 2.5-kDa degradation products, quickly followed by the appearance of multiple peptides of 1 kDa or smaller. The hydrolysate showed a steady increase in solubility and a biphasic change in foaming characteristics with decreasing peptide size. At the highest degree of hydrolysis achieved (22%), the majority of the peptides were smaller than 1 kDa and could be efficiently assimilated by the yeast Kluyveromyces marxianus growing in a defined medium.