True crabs are always part of the catch, especially trawling. Given the lack of direct consumption of crabs in the region, their shell waste can be used as a valuable source of protein to extract antioxidant compounds. In this study, samples of Portunussegnis crabs were collected by trawl nets with apertures of 40 mm from depths of 20 to 30 m from the west coast of Khuzestan province. The enzymes a-chymotrypsin, Trypsin, Pepsin, Papain, Neutrase and Alcalase were used to hydrolyze crab crust proteins. The antioxidant activity of the crab shell was investigated by removing the free radical activity of DPPH, reducing antioxidant power assay and measuring the ACE inhibitory activity of hydrolyzed proteins. The highest radical removal activity of diphenyl picrylhydrazyl (DPPH) was observed for proteins hydrolyzed with chymotrypsin and papain enzymes at 23.67±13.65 and 23.13 02.85, respectively. The lowest reduction power of hydrolyzing enzymes with chymotrypsin was 0.072 and the highest value for papain was 0.122. The level of inhibitory activity of crab shell hydrolyzates showed that the highest activity was related to Papain enzyme (16.20%) and the lowest was related to Alkalase enzyme (12.51%). According to the observations, it seems that crab shell proteins after enzymatic hydrolysis have moderate antioxidant activity, reducing power and inhibition of ACE, and probably after additional research of hydrolyzed proteins of crab exoskeleton as a suitable source of Antioxidant compounds can be used.
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