Degradation of Shrimp Proteins during Fermentation with Lactic Acid Bacteria and Dynamic Changes in Their in Vitro Antioxidant Activity

This study aimed to investigate the degradation of myofibrillar protein (MP) and sarcoplasmic protein (SP) during the fermentation of shrimp meat with Enterococcus lactis as well as the changes in antioxidant activity of the degradation products (peptides). The findings revealed that for both protein extracts, the pH significantly decreased with fermentation time (P < 0.05), and the protease activity significantly increased (P < 0.05) compared to that before fermentation. The results of gel electrophoresis showed that the fermentation resulted in degradation of both proteins, with more pronounced degradation of SP being noted compared to MP. The scavenging capacity against 2,2’-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) radical cation and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical as well as Fe³⁺ reducing power of the two protein extracts were significantly enhanced after the fermentation (P < 0.05), and the antioxidant capacity of the peptides derived from SP was significantly higher than that of the peptides derived from MP (P < 0.05). Correlation analysis showed a significantly positive correlation (P < 0.05, and P < 0.01) between protease activity and the degree of SP hydrolysis and the antioxidant activity of its degradation products. The results of this study indicated that peptides with high antioxidant capacity could be obtained from fermented shrimp proteins with E. lactis, and the peptides derived from SP had higher antioxidant activity. This study provides a theoretical basis for the full utilization of sarcoplasmic proteins produced during aquatic products processing (e.g. surimi) and the development of antioxidant peptides.