Correlation between Antioxidant Activity and Structure and Amino Acid Composition of Protease Hydrolysates from Mung Bean

In this experiment, mung bean protein was enzymolyzed by alkaline protease, neutral protease, pepsin and trypsin, and the antioxidant capacity of the enzymolysis product was determined. The correlation between the enzymolysis product and the structural changes was investigated by combining Fourier transform infrared spectroscopy, SDS-PAGE, circular dichromatography and amino acid analyzer, amino acid composition of the hydrolysates and the correlation between antioxidant activity and structure change were analyzed. The results showed that the 4 h neutral protease hydrolysates of mung bean protein had the strongest antioxidant capacity, with DPPH free radical scavenging rate and hydroxyl free radical scavenging rate reaching 71.03% and 51.94%, TBARS value reaching 0.4045 mg/L and Fe2+ chelating rate reaching 52.31%. Combined with SDS-PAGE, FTIR and CD, it could be concluded that: The antioxidant capacity of mung bean protease hydrolysates was closely related to its molecular weight, secondary structure conformation and amino acid composition. Compared with mung bean protein, the α-helix structure content of mung bean protease hydrolysates increased by 4.12% and the β-fold structure content decreased by 19.99%. The antioxidant activity was closely related to the increase of α-helix content and the decrease of β-folding content. The hydrophobic amino acids and aromatic amino acids that affected antioxidant activity increased by 0.208 g/100 g and 0.207 g/100 g, respectively. The hydrophobic hydrolysates with lower molecular weight less than 10 kDa had better antioxidant activity. Based on the above results, it was confirmed that the activity of mung bean protease hydrolysate had high relation with α-spiral and β-fold.