Study of antioxidant activity of sea cucumber hydrolyzed protein (Holothuria leucospilota) and its effect on microbial and chemical properties of surimi of silver carp

The aim of this study was to investigate the antioxidant effect of cucumber hydrolyzed protein (Holothuria leucospilota) and its effect on microbial and chemical properties of silver carp (Hypophthalmichthys molitrix) at refrigerator temperature. Enzymatic digestion of cucumber muscle was performed using alkalase enzyme (1.5% of weight of raw material, 55 °C and 4hr). Surimi was prepared from silver carp fillet and added to it at two concentrations of 0.5 and 0.1 mg/ kg of hydrolyzed protein. Antioxidant activity, peroxide value (PV), total volatile nitrogen bases (TVB-N), thiobarbituric acid (TBA), pH, volatile fatty acids (FFA), aerobic mesophilic bacterial count and psychrotroph bacteria on 0, 3, 6, 9, 12 and 15 days were performed. The rate of free radical scavenging by cucumber hydrolyzed protein at 0.5 and 0.1 mg/ kg was 92.24% and 62.11%, respectively, which showed a higher value than the commercial antioxidant BHT (p< 0.05). The amount of peroxide in the treatment was 0.1 mg/ kg until the ninth day and in the treatment of 0.5 mg/ kg until the twelfth day was within the allowable range. The results of TVB-N, TBA, FFA, aerobic mesophilic bacterial and psychrophilic bacteria in both treatments and on the days of the study did not exceed the allowable limit. This study showed that cucumber hydrolyzed protein is able to control bacterial load and oxidation process in silver carp surimi. Treatments containing cucumber hydrolyzed protein could increase the shelf life of surimi for 9 days compared to the control treatment.