Structural and functional properties of protein hydrolysates from myofibrillar protein of crocodile (Crocodylus siamensis) meat

In this study, three proteases (papain, neutral protease, bromelain) were employed to hydrolyze crocodile (Crocodylus siamensis) myofibrillar protein (MP), effects of hydrolysis duration on functional and structural properties of MP hydrolysates was investigated. The findings revealed that solubility of all hydrolysates exceeded 60%, with the highest reaching 96.7%. The emulsifying activity of neutral protease hydrolysates exhibited a significant superiority over the other two hydrolysates (P < 0.05). The Fe2+ chelating and DPPH radical scavenging activity of hydrolysates ranged from 20% to 60%, and 60%–90%, respectively. Based on the experiment results, the hydrolysates of papain at 1h, neutral protease at 1h, and bromelain at 2h were used for structural analysis. Compared to MP, the secondary structure of hydrolysates showed a reduction of 9.6%, 15.2%, and 4.7% in α-helix and the increase of 42.4%, 29.6%, and 44.2% in β-fold content of papain, neutral protease and bromelain hydrolysates respectively, suggesting the transition from spiral to folding structure and the exposure of hydrophobic group, which was proved by free amino acid analysis. SEM results confirmed the alterations in MP structure. The molecular weight distributions of three hydrolysates were predominantly below 1000 Da, demonstrating that crocodile MP was effectively hydrolyzed into bioactive peptides.