Correlation between the Degree of Hydrolysis and the Peptide Profile of Whey Protein Concentrate Hydrolysates: Effect of the Enzyme Type and Reaction Time

The use of protein hydrolysates for the development of new food products requires their prior characterization including the determination of the degree of hydrolysis (DH) and the distribution of peptides according to the chain length. In this study, the DH of whey protein concentrate hydrolysates was determined by four methods (formol titration, soluble protein content, ortophtalaldehyde and osmometry) and the peptide profile was characterized by size-exclusion high performance liquid chromatography. The correlations among the four methods as well as between the DH and peptide profiles were established. The highest DH values were obtained by the methods of the soluble protein content (44.7%) and the derivatization with ortophtalaldehyde (20.17%) for the proteases from Bacillus licheniformis and Aspergillus sojae, respectively. The use of the Bacillus licheniformis protease was more advantageous because it produced the highest contents of di-and tripeptides (8.79%) and the lowest of large peptides (53.57%). A significant correlation (p < 0.05) between the DH and the contents of peptides and free amino acids was observed and the intensity of the correlation varied as a function of the method and the enzyme type analyzed.