Shrimp shell wastes: Optimization of peptide hydrolysis and peptide inhibition of alpha-amylase

Response surface methodology coupled with a Box-Behnken design (RSM-BBD) was used to optimize neutrase concentration (A: 4-6% (w/w)), liquid-solid ratio (B: 10-20 mL/g) and hydrolysis time (C: 3-5 h) to obtain shrimp shell wastes hydrolysates with a-amylase inhibitory activity. The optimum conditions were enzyme concentration of 5.4% (w/w), liquid-solid ratio of 13 mL/g, time of 4.1 h, temperature of 50 degrees C and pH of 7.0. Under these conditions, the alpha-amylase inhibitory rate was 43.4%, in agreement with the prediction model with a coefficient of determination (R-2) of 0.9676. Shrimp shell wastes hydrolysates showed significant ability to scavenge diphenyl picryl hydrazinyl free radicals, reduce iron (III) and inhibit lipid peroxidation. Shrimp shell waste hydrolysates consisted mainly of small peptides with molecular weights less than 4 kDa and high essential amino acids (278 mg/g), which indicated its high nutritional value based on the FAO/WHO recommended standard protein. The results showed that shrimp shell waste hydrolysates contained valuable components that could be converted into useful and potentially high-value products.