Microwave-assisted digestion of β-lactoglobulin by pronase, α-chymotrypsin and pepsin

The effects of microwave irradiation (MWI) on kinetic parameters for pronase, α-chymotrypsin and pepsin hydrolysis of bovine β-lactoglobulin (β-Lg) were evaluated. The experiments were performed under MWI or conventional heat (CH) at 40 °C. The initial velocity (V0) of peptide bonds cleavage was measured by o-phthaldialdehyde method; the peptide profile was analysed by sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS–PAGE). Higher catalytic effectiveness (KcatKm−1) values were obtained in the pronase and α-chymotrypsin digestions performed under MWI (7793 and 2073 min−1 mM−1, respectively) in comparison with the values in the respective CH digestions (1802 and 941 min−1 mM−1, respectively). The Michaelis–Menten constant (Km) for either enzyme was reduced under MWI. Pepsin showed very low activity on β-Lg at pH 4.0 regardless of the heating procedure used. For two enzymes, pronase and α-chymotrypsin, differences in SDS–PAGE profiles were obtained due to the MWI applied during the enzymatic hydrolysis. The combined enzyme/MWI treatments could have a relevant application in the development of β-Lg hydrolysates.