Antioxidant and antimicrobial peptide fractions from squid and tuna skin gelatin

Abstract

Gelatin extracted from tuna skins and giant squid tunics were hydrolysed with Alcalase at 50ºC for 3h. Two peptide fractions (1-10K and ≤1K) were obtained from each gelatin hydrolysate by subjecting them to centrifugal ultrafiltration using successively a 10 kDa and a 1 kDa membrane. The peptide fractions were characterized in terms of amino acid composition and Fourier transform infrared (FTIR) spectroscopy. Antioxidant properties were tested according to the Ferric Reducing Antioxidant Power (FRAP) assay and the radical scavenging capacity (ABTS) assay. A disk diffusion test was performed to test antimicrobial action against a panel of Gram-positive and Gramnegative pathogenic and fish spoilage-associated microorganisms. Although antioxidant and antimicrobial properties could be detected in all tested peptide fractions, the lowermost molecular weight fraction from squid hydrolysate presented the highest reducing and radical scavenging capacities, whereas microbial growth inhibition was found to be specifically related to the type of microorganism.