Effect Of Degradation In Grass Carp(Ctenopharyngodon Idella) Myofibrillar Structural Protein On Texture At Low Temperature

Texture deterioration to different extents occurs in freshwater fish during preservation,which affects the edible quality of fish seriously.Previous studies in our laboratory have shown that actomyosin was degraded by endogenous proteases during the preservation,resulting in the deterioration of the textural quality of fish muscle.However,the muscle structure of fish is delicate and complex,and the degradation of actomyosin is not enough to fully explain the deterioration of muscle.Myofibrillar structural proteins play a role in linking and maitaining myofibrillar structure,which also have great significance for the stability of texture.However,little research has been done on myofibrillar structural proteins in fish systems.Therefore,the aim of this study was to determine the relationship between degradation of myofibrillar structural proteins and texture deterioration of grass carp(Ctenopharyngodon idella).Furthermore,the role of endogenous protease system in the degradation of myofibrillar structural proteins were revealed,and the effect of relevant myofibrillar structural proteins on the texture of grass carps was also studied.Firstly,the relationship between the degradation of myofibrillar structural proteins and the texture deterioration of dorsal muscle of grass carp during ice or superchilling storage was studied by measuring the quality indexes such as ultrastructure,shear force and water holding capacity,in combination with polyacrylamide gel electrophoresis(SDS-PAGE)and western blotting technology.The results showed that the degradation degree of myofibrillar structural proteins(titin,nebulin,desmin,troponin T)increased with the extension of storage time.respectively,during 21 days of storage,while the hardness of fish decreased by 75.60%～85.39%.and the fragmentation index increased by 2.78～2.94 times,the M line and the Z line completely disappeared,and the light and dark bands were blurred.The sarcoplasmic reticulum was dissolved and the tissue structure was completely dissociated.There was a significantly positive correlation between shear force and myofibrillar structural protein degradation(p<0.05).Secondly,the effects of different endogenous proteases on the degradation of protein and the texture of grass carp were studied.The apoptosis enzyme inhibitor(AC-DEVD-CHO),cathepsin inhibitor(E64)and calpain inhibitor(EDTA-2Na)were added to the fish by soaking method,and the effects of different endogenous proteases on the degradation of myofibrillar structural proteins and texture of grass carp were studied under ice-storge.The results showed that the endogenous enzyme inhibitor treatment group can effectively slow down the degradation of myofibrillar structural proteins,the shear force in AC-DEVD-CHO treatment group increased by 36.61%and the the myofibril fragmentation index decreased by 52.25%during the first 3 days of ice-storage.The shear force in E64 treatment group increased by 17.52%and the myofibril fragmentation index decreased by 39.21%after 21 days of ice-storage.Furthermore,Endogenous proteases play an important role in the degradation of myofibrillar structural proteins.the effect of apoptotic enzymes was significant during the first 3 days of ice-storage and cathepsins and calpain-activated proteases played a role in the deterioration of texture during the whole storage.In this paper,the relationship between the degradation of skeletal proteins and the degradation of fish texture and the role of endogenous proteases were studied.This paper will provide an important theoretical guidance for solving the technical problems of the industrialization of freshwater fish preservation,and is of great practical significance for optimizing fishery structure,realizing fishery efficiency increase and increasing fishery and agricultural income.