Protease inhibitors: Its effect on striped catfish (Pangasianodon hypophthalmus) surimi shelf life during frozen storage

Abstract

Surimi, a processed fish product, is widely utilised for making seafood delicacies such as imitation crab and fish balls. Endogenous enzymes found naturally in fish can contribute to surimi breakdown if they are not properly controlled during processing and storage. Enzymes like proteases and lipases can alter the texture, flavour, and overall quality of the surimi product over time. Protease inhibitors produced by legumes can be utilized to reduce surimi degradation due to endogenous proteases. Soybean extract and many legume seeds contain compounds called phytochemicals and peptides that may have antibacterial properties. The effect of a protease inhibitor derived from soyabean on fish muscle homogenate found that the sample has 72.19±0.68% protease activity at room temperature and a protein content of 8.83±0.60 g/ml. However, with the addition soyabean extract the gel strength of surimi was found to be increased significantly and the other functional characteristics of striped catfish surimi improved during the frozen storage. But after 4th month of storage the decreasing trend was observed in all the parameters. Throughout the storage period, high gel strength values were observed in surimi treated with soyabean extract. SDS-PAGE image with the increase in the storage period, MHC band intensity reduced, while there was no change in the actin bands. The surimi added with protease inhibitor (Soyabean extract) also maintained good physio-chemical properties than untreated surimi during period of 6th month of which was due to the protease inhibition and anti-microbial properties of soyabean extract.