Inhibitory effect of edible natural compounds with di- and tri-carboxyl moiety on endogenous protease inducing disassembly and degradation of myofibrils from grass carp (Ctenopharyngodon idella)

Inhibition of endogenous protease is a rapid and feasible approach to control the proteolysis proceeding of post mortem fish flesh. In the present study, the in vitro inhibitory effects of common edible di- and tri-carboxylic acids and salts on endogenous proteolytic activities as well as myofibrillar disassembly and degradation mediated by crude enzyme of grass carp muscle were investigated. The results showed that among the compounds tested, maleic acid, fumaric acid, tartaric acid and malic acid were the most effective inhibitor for cathepsin B, L and calpain, with IC50 ranging from 7.76 to 30.13 mM, from 32.38 to 65.12 mM, from 1.06 to 6.76 mM, respectively. Also, relatively lower Ki (ranging from 1.04 to 43.21 mM) of these compounds were found towards cathepsin B, L and calpain. Incubation of myofibrillar protein with crude enzyme in the presence of di- and tri-carboxylic compounds could remarkably suppress the dissociation and degradation of myosin heavy chain (MHC), and ameliorate the loss of heat shock protein (HSP) in myofibrils, with tartaric acid and fumaric acid proved more effective than other compounds, possibly implicating their application as potential and efficient inhibitors for quality control of fish muscle products.