Optimization of enzymatic hydrolysis of shrimp waste for recovery of antioxidant activity rich protein isolate.

Shrimp waste is an important source of astaxanthin, which occur as a complex with proteins, and protein isolates as well as carotenoids are known to possess antioxidant activity. Investigations were carried out to optimize hydrolysis of shrimp waste using a bacterial protease to obtain antioxidant activity rich protein isolate. The effect of three process variables namely enzyme concentration to waste, incubation temperature and time on carotenoid recovery, protein content, trichloro acetic acid (TCA) soluble peptide content and DiPhenyl Picryl Hydrazylchloride (DPPH) scavenging activity was evaluated using a fractionally factorial design. A high correlation coefficient (>0.90) between the observed and the predicted values indicated the appropriateness of the design employed. Maximum carotenoid recovery was obtained by hydrolysing the shrimp waste with 0.3 % enzyme for 4 h. DPPH radical scavenging activity of carotenoprotein isolate was markedly affected by enzyme concentration, temperature and time of hydrolysis. The study indicated that in order to obtain the carotenoprotein from shrimp waste with higher carotenoid content hydrolysing with an enzyme concentration of 0.2-0.4 %, at lower temperature of 25-30° upto 4 h is ideal. However, in order to obtain the protein isolate with increased antioxidant activity hydrolysing at higher temperature of 50 °C, with higher enzyme concentration of 0.5 % for shorter duration is more ideal.