Influence of salts on hydrolysis of β-lactoglobulin by free and immobilised trypsin

Immobilised trypsin is an alternative to free trypsin for producing protein hydrolysates with increased functionalities. However, the influence of hydrolytic conditions on this process remains unclear. The influence of salts on β-lactoglobulin (β-Lg) hydrolysis by free and immobilised trypsin was compared. For both forms of trypsin, 0.1 m Tris accelerated the release of most final peptides except f (71–75), and had no significant effects on the hydrolysis of intact β-Lg. Increasing NaCl concentrations from 0 to 0.02 m increased the degree of hydrolysis (DH) by 22.4% for free trypsin versus 62.1% for immobilised trypsin. The presence of 0.1 or 0.5 m NaCl hindered the release of peptides associated with the breakdown of intact protein. This led to 2–4 fold decreases in depleting intact β-Lg and DH, except immobilised trypsin at 0.1 m NaCl (DH increased by 44.3% versus without NaCl). Potential mechanisms underlying the effects of salts are discussed.