Proteolytic Analysis of Different Tuna (Thunnus albacares) Viscera for Obtaining Protein Hydrolysates

This project aims to obtain and characterize protein hydrolysates from the solid residues (dark muscle) and effluents (cooking water) generated from the processing of yellowfin tuna (Thunnus albacares) and evaluate their potential to be applied as organic fertilizer in farming. From the studied viscera (stomach, pyloric blind, liver, pancreas, and intestine), it was found that the pyloric blind of the tuna digestive system represents an adequate source of alkaline proteases that act on the dark muscle of tuna and cooking water, at pH optimum of 10.5 and temperature of 50 °C. The results of SDS-PAGE electrophoresis and enzymatic inhibition indicate that the proteolytic activity exhibited by the enzymatic extract of the pyloric blind of tuna is mainly due to serine protease enzymes, especially trypsin type, and it showed a proteolytic activity similar to that of a commercial protease coming from Bacillus sp. It is possible to use these enzymes in processes that require pH values between 8 and 11 and mild temperatures conditions (30-50°C). The cooking water showed a low yield and high ash content, which may decrease the protein hydrolysates' nutritional quality and functional properties.