Effects of in vitro oxidation on myofibrillar protein charge, aggregation, and structural characteristics

The effects of oxidation degree on the isoelectric point (pI), aggregation, and structural characteristics for pork myofibrillar protein (MP) were studied by employing extracted MP, which was incubated by using a hydroxyl radical oxidation system. The concentrations of hydrogen peroxide (H₂O₂) were 0, 0.5, 1, 3, 5, 10, and 20 mM. With the increased oxidation degree, the contents of α-helix, ionic bonds, and hydrogen bonds decreased significantly (P < 0.05). Moreover, the pI value and total amino acids showed a declining trend, and the β-sheet as well as solubility rised firstly and then declined. On the contrary, random curl, β-turn, and turbidity increased significantly (P < 0.05). Therefore, amino acid side chain groups were modified, and the opposite effect, caused by oxidation that leads to protein cross-linking and aggregation, was greater than the promotion effect, such as net negative charge, these are the main factors that leads to the instability of protein solution systems.