真空冷藏条件下罗非鱼内源蛋白酶对鱼片质构劣化的作用

Function of tilapia endogenous proteases in deterioration of vacuum-refrigerated fillet texture

  • 摘要: 【目的】探究冷藏期间造成罗非鱼鱼肉质构品质劣化的关键蛋白酶,为提升冷藏鱼肉品质提供理论依据。【方法】对罗非鱼鱼片进行真空包装,于4℃下冷藏,在0~6 d内对鱼肉进行质构、pH、肌原纤维小片化指数(MFI)、内源蛋白酶活性及在不同细胞器的分布和肌原纤维SDS-PAGE图谱测定,并通过皮尔逊相关分析确定冷藏期间造成鱼肉质构劣化的关键蛋白酶。【结果】冷藏过程中,罗非鱼鱼肉pH呈先降低后升高的变化趋势,最终pH为6.68;硬度和MFI分别呈下降和升高的趋势;组织蛋白酶B+L活性变化整体表现为升高趋势,第6 d时活性为初始值的1.27倍,在肌原纤维、肌浆蛋白和线粒体中活性呈先上升后下降的变化趋势,在溶酶体中活性呈下降趋势;组织蛋白酶B、D活性变化整体表现为先升高后降低,且均在第4 d达最大值,分别为初始值的1.20和1.48倍,肌原纤维、肌浆蛋白和线粒体中的组织蛋白酶B活性呈先升高后降低的变化趋势,溶酶体中的组织蛋白酶B活性呈下降趋势,肌原纤维和肌浆蛋白中的组织蛋白酶D活性呈升高趋势,溶酶体和线粒体中的组织蛋白酶D活性呈降低趋势;钙离子浓度呈升高趋势,钙激活蛋白酶活性呈先升高后降低的变化趋势;肌原纤维蛋白SDS-PAGE图谱中肌球蛋白重链、肌动蛋白和肌球蛋白轻链的条带逐渐减少和模糊;组织蛋白酶B、B+L活性与鱼肉硬度呈极显著负相关(P<0.01,下同),与鱼肉MFI呈极显著正相关;组织蛋白酶D和钙激活蛋白酶活性与鱼肉硬度和MFI无显著相关性(P>0.05)。【结论】组织蛋白酶B和组织蛋白酶L参与肌原纤维蛋白的降解和线粒体介导的细胞凋亡,可能是冷藏期间罗非鱼鱼肉质构劣化的2个关键靶点酶,可采取有效技术手段对其活性进行抑制,进而提升贮藏期间鱼肉质构品质。

     

    Abstract: 【Objective】To investigate key proteases that caused deterioration of tilapia meat texture quality during refrigeration,and to provide a theoretical basis for refrigerated fish meat quality improvement.【Method】Tilapia fillets were vacuum-packed and refrigerated at 4 ℃, and texture, pH, myofibril fragmentation index(MFI), endogenous protease activity,endogenous protease distribution in organelles and myofibril SDS-PAGE profiles were determined during 0-6 d. Key proteases that caused the deterioration of fish meat texture during refrigeration were identified through Pearson correlation analysis.【Result】 pH of tilapia fish meat decreased and then increased during refrigeration, with a final pH of 6.68; hardness decreased but MFI increased;cathepsin B+L activity increased overall as it was 1.27 times of its initial value on 6 d,and it first increased and then decreased in myofibril,myogen and mitochondria but it decreased in lysosome; cathepsin B activity and cathepsin D activity increased and then decreased,and they both reached the maximum on 4 d, which were 1.20 times and 1.48 times of their initial values,respectively. Cathepsin B activity in myofibril,myogen and mitochondria first increased and then decreased but it decreased in lysosome;cathepsin D activity increased in myofibril and myogen,but it decreased in lysosome and mitochondria;calcium ion concentration increased and calcium-activated protease activity first increased and then decreased;myofibrillar protein SDS-PAGE profile showed that bands of myosin heavy chain,actin,and myosin light chain became less and blurred;cathepsin B activity and cathepsin B+L activity had an extremely negative correlation with fish meat hardness (P<0.01, the same below),and they also had an extremely negative correlation with MFI of fish meat;cathepsin D activity and calcium-activated protease activity were not significantly correlated with fish meat hardness or MFI(P>0.05).【Conclusion】 Cathepsin B and cathepsin L participate in myofibrillar protein degradation and mitochondria-mediated apoptosis,and such situation may be attributed to the two key target enzymes for tilapia meat deterioration during refrigeration. Available techniques can be taken to inhibit their activity to improve fish meat texture quality during storage.

     

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