Antioxidative properties and hydrolysis profile of Skipjack tuna dark muscle and skin.
Alcalase and Flavourzyme hydrolysates from Skipjack tuna (Katsuwonus pelamis), dark muscle and skin, were studied for their antioxidative properties. Time-dependent changes in degree of hydrolysis (DH) and nitrogen recovery (NR) were found to be linearly increase with enzyme concentration (R2>0.98). Ferric reducing antioxidant power (FRAP) and 1,1-diphenyl2-picrylhydrazyl (DPPH) scavenging capacity were found to increase with increasing enzyme (Alcalase and Flavourzyme) hydrolysis; hydrolysates of a same DH were different in antioxidant properties. DPPH scavenging capacity showed strongest dependence on DH for dark muscle-Alcalase hydrolysates (DAL) reaching up to 70% scavenging capacity. SkinAlcalase hydrolysates (SAL) were characteristically in stronger scavenging activities in an intermediate DH depending on enzyme concentration. IC50 values (DPPH) for dark muscle hydrolysates were 2 times lower than IC50 for skin hydrolysates. Reducing power (FRAP) of hydrolysate peptides increased with hydrolysis time and then slightly decrease. Dark muscle tuna and skin hydrolysates potentially could be further developed into functional food ingredients with biological activities which remain to be further investigated.