Effects of High Pressure Modification on Conformation and Digestibility Properties of Oyster Protein

To expand the utilization of oyster protein (OP), the effects of high pressure (100 to 500 MPa) on chemical forces, structure, microstructure, and digestibility properties were investigated. High pressure (HP) treatment enhanced the electrostatic repulsion (from -13.3_Control to -27.8_HP200 mV) between protein molecules and avoided or retarded the formation of protein aggregates. In addition, the HP treated samples showed uniform distribution and small particle size. The changes in electrostatic interaction and particle size contributed to the improvement of solubility (from 10.53%_Control to 19.92%_HP500 at pH 7). The stretching and unfolding of protein were modified by HP treatment, and some internal hydrophobic groups and -SH groups were exposed. HP treatment modified the secondary structure of OP. The treated samples contained less α-helix and β-sheet structures, whereas the proportions of β-sheet and random coil structures were increased. The treated samples have high digestibility in the stomach (from 26.3%_Control to 39.5%_HP500) and in the total digestive process (from 62.1%_Control to 83.7%_HP500). In addition, the total digestive production showed higher percentages of small peptides (<1 kDa) after HP treatment. The protein solubility and digestibility were increased after HP treatment, and high solubility and high digestibility might increase the chance that OP become a kind of protein supplement.