Effects of ultrasound pretreatment on enzymolysis of sodium caseinate protein: Kinetic study, angiotensin-converting enzyme inhibitory activity, and the structural characteristics of the hydrolysates
Mohammed Adam Yahya Abdualrahman, Cunshan Zhou, Yanyan Zhang, Abu ElGasim Ahmed Yagoub, Haile Ma, Li Mao, Kai Wang
Journal of Food Processing and Preservation
Effects of ultrasound frequency and power density on enzymolysis of sodium caseinate (NaCas) and on the structure of the protein hydrolysate were studied. Enzymolysis kinetics, angiotensin-I converting enzyme (ACE) inhibitory activity, atomic force microscopy (AFM), scanning electron microscopy (SEM), intrinsic fluorescence and the circular dichroism (CD) were determined. Ultrasound significantly (p < .05) increased the degree of hydrolysis (DH), conversion rates of protein, ACE inhibitory activity and the apparent breakdown rate (kA) but decreased the apparent constant (kM). AFM revealed that sonication increased the protein particles diameters, and Rq and Ra values. Fluorescence spectra and SEM images show increases in surface areas of NaCas. CD spectra revealed increases in β-sheet, β-turn and random coil by 20, 5.33 and 5.91%, respectively, and decreased α-helix by 8.82%. Overall, ultrasound successfully improved enzymolysis of NaCas and release more ACE inhibitory activity due to the increases in specific surface area of protein molecule.
Circular dichroism, Secondary structure, Biochemistry, Food science