RECOVERY OF PROTEINS FROM SILVER CARP BY‐PRODUCTS WITH ENZYMATIC HYDROLYSIS AND REDUCTION OF BITTERNESS IN HYDROLYSATE

Abstract

ABSTRACT The by‐products of silver carp (Hypophthalmichthys molitrix) filleting were hydrolyzed to extract protein to reduce the environmental problems caused by the wastes from filleting and to increase the economical values of silver carp processing. Enzymatic hydrolysis of silver carp by‐products from filleting and subsequent mechanism research of bitterness reduction in hydrolysate were performed in this paper. First, the effects of various enzymatic treatments with neutral protease, papain, protamex, Flavourzyme, neutrase and papain combination (NPC) and neutrase and flavourzyme combination (NFC) protease on the degree of hydrolysis (DH), the degree of solubilization of protein and the bitter taste value were compared; the NFC was found to be the best. Second, on the basis of orthogonal tests, the optimal hydrolysis condition was done with 0.5% of the NFC at pH 7.5 and 50C. Finally, the effects of two pretreatments including heating and fat removing on DH were investigated. Results showed that these two pretreatments were not beneficial to enzymatic hydrolysis of silver carp by‐products.PRACTICAL APPLICATIONSMore than 50% of total fishery products were discarded as inedible by‐products every year in China. We have developed a technology for recovery of proteins from the by‐products of silver carp filleting using enzymatic hydrolysis. The degree of solubilization of protein was 82.4% and bitter taste value of hydrolysates was less than 1.0 (meaning hardly any bitterness). The technology can not only save the valued protein resources in the by‐products of fish processing but can also be used to process other similar fish by‐products to reduce the environmental problems caused by the wastes from filleting through being improved slightly, and increase the economical values of fishery products processing.