Influence of Cold Storage on the Quality of Muscle and the Activity of Cathepsin H in Red Shrimp(Solenocera crassicornis)

To investigate the changes of cathepsin H activity and muscle quality of shrimp (Solenocera crassicornis) under different conditions, the samples were refrigerated at 4 °C for 6 days and frozen at -18 °C for 120 days, respectively. The changes of pH, water retention, hardness, springness, myofibrillar protein content, water content, and cathepsin H activity in intact shrimp and beheaded shrimp were compared and analyzed during chilling storage. Results showed that, with the increasing of storage period, the pH of muscle from the whole shrimps and beheaded shrimps both increased continuously, while the increasing rate of beheaded shrimp was slightly lower than that of whole shrimp samples. The myofibrillar protein (MP) content of both shrimp muscle decreased gradually with the prolonging of storage time. The MP content in intact shrimp and beheaded shrimp group decreased by 38.32% and 30.88% after refrigerated for 6 days, and by 61.67% and 52.09% after frozen for 120 days, respectively. During the whole frozen storage, the hardness and springness of the two groups of shrimps increased first and then decreased, while during the cold storage, the hardness and springness of the two groups of shrimp always decreased. The changes of cathepsin H activity in different subcellular fractions were different. The activity of cathepsin H in frozen condition was lower than that in cold condition, and the activity of cathepsin H in intact shrimp group was higher than that in beheaded shrimp group. The results showed that compared with the whole shrimp, the storage of beheaded shrimp was more conducive to the protection of muscle quality, and the activity of cathepsin H enzyme was greatly affected by the storage temperature. The results would provide a theoretical basis for the changes of physicochemical properties and cathepsin activity of shrimp under different conditions.