Relevance of cathepsins activity and texture in slightly acidic electrolyzed water-slurry iced mackerel(Pneumatophorus japonicus)

The incorporation of SAEW and SI can effectively maintain the characteristics of texture in marine fish.This study aimed to investigate the relevance of cathepsin activity for texture and the establishment of a shelf-life model of mackerel(Pneumatophorus japonicus)stored at 4◦C.Before the cold storage,mackerel samples were exposed to flake ice(Control),slurry ice(SI),and slightly acidic electrolyzed water-slurry ice(SAEW-SI),respectively.Then the TVC,K-value,cathepsin activity,texture,and sensory attributes were investigated.The results showed that the TVC and K-value of samples in SAEW-SI group was significantly lower by approximately 1 log CFU/g and 17%than those in Control group(P<0.05).Meanwhile,there was a tendency to first increase and then decrease on the activities of cathepsin B,D and L.Results of texture profile analysis(TPA)clarified that SAEW-SI can markedly suppress the decrease of hardness,springiness and chewiness(P<0.05).During the experimental period,the highest sensory scores were obtained in SAEW-SI group.In addition,the heat map of correlation analysis suggested that texture attributes(hardness)were negatively correlated with cathepsin B(r=-0.66),cathepsin D(r=-0.49),and cathepsin L(r=-0.69),respectively.According to the principal component analysis(PCA)and analysis of linear regression,SAEW-SI treatment could effectively maintain mackerel quality and extend the estimated shelf-life of mackerel by at least 5 days compared to Control group.Therefore,SAEW-SI could be suggested as a novel strategy for cold-chain transportation in seafood industry.