Preparation and antioxidative activity of hoki frame protein hydrolysate using ultrafiltration membranes

Hoki frame protein, which is normally discarded as an industrial by-product in fish plants, was hydrolyzed with various enzymes. The antioxidative activity of the hydrolysates was investigated, and the results showed that pepsin hydrolysate has the highest activity. Hoki frame protein hydrolysates (HPH) prepared by pepsin were fractionated according to the molecular mass into four major types, HPH I (5–10 kDa), HPH II (3–5 kDa), HPH III (1–3 kDa), and HPH IV (below 1 kDa), using an ultrafiltration membrane. HPH III showed a higher antioxidative activity than the other hydrolysates in a linoleic acid emulsion system. In addition, the free-radical scavenging activities of the fractionated hydroysates were evaluated using electron spin resonance spectroscopy. The results showed that HPH III has the highest scavenging effects for 1,1-diphenyl-2-picrylhydrazyl, hydroxyl, alkyl and superoxide anion radicals, and the inhibition pattern was dose-dependent.