Biochemical Properties and Biomarker of Muscle Softening of Shrimp Litopenaeus vannamei During Cold Storage
[Objective]The aim of this study is to investigate the effects of biochemical properties on the textural quality deterioration of Litopenaeus vannamei during cold storage and to identify the biomarker.[Methods]The changes in muscle textural attributes were monitored with texture analyzer,and the contents of glycogen lactate,ATP levels,and the activities of Ca2+-ATPase,and acid,alkaline phosphatase(ACP,AKP)were accordingly determined with the corresponding biochemical assay kits.In addition,the characteristics of anaerobic metabolism and the dynamic changes were clarified according to the variation of phosphorylation-regulating enzyme activities.Subsequently,the interrelationships between these indicators were examined with correlation analysis.[Results and Conclusion]The rapid decrease in texture indicators was observed,and the hardness of shrimp significantly decreased to(2 947±113)g after 72 h of refrigeration(P<0.05),and a negative correlation was found between the textural attributes and the myofibril fragmentation index(MFI)(P<0.01).The activity of Phosphofructokinase(PFK)significantly decreased to(20.82±0.38)U/mg after 24 h of refrigeration(P<0.05)and exhibited the strongest correlation with glycolysis indicators,suggesting its close involvement in initiating and speeding up the process of muscle softening.The ATP content regulated the activity of phosphatase and Ca2+-ATPase,while the ACP activity and AKP activity significantly decreased during refrigeration,among which the ACP and AKP activities increased rapidly to(16.39±1.17)U/mg and(0.86±0.05)U/mg(P<0.05),respectively,after 96 h of refrigeration.Additionally,Ca2+-ATPase activity decreased to(0.50±0.01)U/mg(P<0.05)after 24 h of refrigeration.The decrease in Ca2+-ATPase activity over time triggered the release of Ca2+-induced phosphatases from the endoplasmic reticulum,and initiated the dephosphorylation process.This process activates the protein degradation signals,leads to the ubiquitination labeling,and subsequently triggers the degradation of myofibrillar proteins.Furthermore,correlation analysis reveals the primary role of Ca2+-ATPase in driving the texture deterioration of shrimp during cold storage.
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