Enzymatic Hydrolysis of Caseins by Two Different Proteases and Their Effect on Functional Properties of Resulting Protein Hydrolysates

Sodium caseinate (88.03% protein based on dry weight) was hydrolyzed by Alcalase 2.4L and Protamex to 5%, 10%, 15% and 20% degree of hydrolysis (DH) respectively. Sodium caseinate and its hydrolysates were analyzed, compared and used for measuring some functional properties. All hydrolysates were different from intact sodium caseinate in protein, moisture, and ash content. Free amino groups increased through the course of hydrolysis and the increase was related to DH. From HPLC data, the produced peptides had smaller molecular sizes and their average molecular weight (Mw) was below 8103Da. Mw decreased as the DH increased while all the resulting peptides after 15% DH showed 20% DH showed Mw below 5043 Da for both alcalase 2.4L and protamex. Protein solubility increased with increasing DH and all hydrolysates were from 84.8%～98% soluble between pH4.0～5.0 at 10%～20% DH. This result indicated solubility improvement of sodium caseinate at its isoelectric pH. All hydrolysates showed poor emulsifying and foaming properties comparatively to the unmodified sodium caseinate even if they formed high initial foam levels (59.03±0.15ml to 43.12±0.67ml). The global amino acid compositions did not differ signifi- cantly between the different hydrolysates and they were very close among sodium caseinate and its hydrolysates.