冻结方式对中华鲟脂质氧化和肌纤维微观结构的影响

Effects of Freezing Methods on Lipid Oxidation and Microstructure of Muscle Fibers in Acipenser sinensis

为研究中华鲟鱼肉冻藏过程中脂质氧化造成的品质劣变。将中华鲟鱼块分别采用冰柜(-20、-50℃)和液氮(-80、-110℃)冻结后置于-18℃冰柜中冻藏24周,测定中心温度、脂肪质量分数和游离脂肪酸(free fatty acids,FFAs)相对含量、脂肪酸组成、过氧化值(peroxide value,POV)、硫代巴比妥酸反应物(thiobarbituric reactive substances,TBARS)值、荧光化合物含量,观察鱼肉肌纤维微观结构,以探讨不同冻结方式对中华鲟冻藏过程中脂质氧化和肌纤维微观结构的影响。结果显示,随冻藏时间的延长,鱼块脂肪质量分数和多不饱和脂肪酸(polyunsaturated fatty acids,PUFAs)相对含量下降,FFAs相对含量、POV、TBARS值及饱和脂肪酸(saturated fatty acids,SFAs)、单不饱和脂肪酸(monounsaturated fatty acids,MUFAs)相对含量及荧光化合物含量上升,肌纤维结构间隙变大,肌原纤维断裂。但其中液氮冻结组鲟鱼块的脂肪质量分数和PUFAs相对含量高于冰柜冻结组(冻藏结束时,-20℃冰柜冻结组脂肪质量分数为7.89%,-80℃液氮冻结组脂肪质量分数为9.13%),而POV、TBARS值及FFAs、SFAs、MUFAs相对含量和荧光化合物含量显著低于冰柜冻结组(P<0.05),且肌纤维结构也保持较完整。以上结果表明,液氮冻结减轻了中华鲟冻藏过程中肌纤维损伤和脂质水解的程度,从而减缓了脂质氧化的速度。

This study was executed in order to investigate quality deterioration caused by lipid oxidation during the frozen storage of Acipenser sinensis.Fish pieces were stored at−18℃for 24 weeks after being frozen using a freezer(−20 or−50℃)or liquid nitrogen(−80 or−110℃).The central temperature,fat and free fatty acid(FFA)contents,fatty acid composition,peroxide value(POV),thiobarbituric reactive substance(TBARS)value,and fluorescent compound content were measured and the microstructure of muscle fibers was also observed during the storage period for the purpose of evaluating the influence of freezing methods on lipid oxidation and muscle microstructure in Acipenser sinensis during frozen storage.The results showed that with increasing storage time,the fat and polyunsaturated fatty acid(PUFA)contents of the four fish samples decreased,while POV,TBARS value,and the contents of FFAs,saturated fatty acids(SFAs),monounsaturated fatty acids(MUFAs)and fluorescent compounds increased.The gap between muscle fibers increased,which was accompanied by breaking of myofibrils.In addition,the contents of fat and PUFAs in liquid nitrogen frozen samples were significantly higher than those in freezer frozen ones(at the end of storage,the freezer frozen sample frozen at−20℃contained 7.89%of fat compared to 9.13%for the liquid nitrogen frozen one at−80℃),while POV,TBARS value,and the contents of FFAs, SFAs, MUFAs and fluorescent compounds were significantly lower than those in freezer frozen samples (P < 0.05), and the muscle fiber structure was more complete. The above results indicated that liquid nitrogen frozen alleviated the degree of myofibrillar damage and lipid hydrolysis in Acipenser sinensis during frozen storage, thereby reducing the speed of lipid oxidation.