Physicochemical properties, biological activities, and peptidome profile of grass carp swim bladder collagen hydrolysates

This study investigated the physicochemical properties and biological activities of hydrolysates derived from grass carp swim bladder collagen through enzymatic hydrolysis using Papain, Alcalase, Flavourzyme, and Neutrase. The results indicated that the select of protease significantly influences the degree of hydrolysis (DH), molecular weight distribution (MW), trichloroacetic acid-nitrogen solubility index (TCA-NSI), structure, and bioactivities of the hydrolysates. The hydrolysate of Alcalase (HA) exhibited the highest DH, TCA-NSI, Fe2+ chelating activity, 1,1-diphenyl-2-picrylhydrazyl (DPPH) scavenging activity, and angiotensin-converting enzyme (ACE) inhibitory activity. Pearson's correlation and principal component analysis (PCA) revealed strong interrelationships among the DH, TCA-NSI, beta-sheet content, Fe2+ chelating activity, ACE inhibitory activity, and short peptide content within the hydrolysates (|r| > 0.80, P < 0.05). A total of 524 peptides were identified from HA, and 20 novel peptides with no toxicity, no allergenicity, and potential bioactivity were discovered by in silico strategy. Molecular docking analysis revealed that hydrophobic interactions and hydrogen bonds were the primary interaction forces between the peptides with free radicals and ACE. These findings provide a foundation for the high-value utilization of grass carp swim bladder hydrolysates as bioactive peptides in the food industry, enabling the sustainable utilization of freshwater swim bladder by-products.