Enzyme-Induced Gelation of Extensively Hydrolyzed Whey Proteins by Alcalase: Comparison with the Plastein Reaction and Characterization of Interactions

Extensive hydrolysis of whey protein isolate by Alcalase 2.4L produces a gel. The objectives of this study were to compare enzyme-induced gelation with the plastein reaction by determining the types of interactions involved in gelation. The average chain length of the peptides did not increase during hydrolysis and reached a plateau after 30 min to be ∼4 residues, suggesting that the gel was formed by small molecular weight peptides held together by non-covalent interactions. The enzyme-induced gel network was stable over a wide range of pH and ionic strength and, therefore, showed some similarities with the plastein reaction. Disulfide bonds were not involved in the gel network. The gelation seems to be caused by physical aggregation, mainly via hydrophobic interactions with hydrogen bonding and electrostatic interactions playing a minor role. Keywords: Whey proteins; enzymatic hydrolysis; Alcalase; aggregation; plastein reaction; peptides; hydrophobic interaction