速冻方式对冷冻贮藏中大口黑鲈鱼肉蛋白质特性的影响

Effects of Different Quick-freezing Methods on Protein Properties of Largemouth Bass(Lateolabrax japonicus)

本文以大口黑鲈为原料,为研究不同降温速率(液氮速冻(1.81℃)、冷冻液速冻(0.15℃)、平板速冻(0.14℃))对冷冻贮藏中(0、1、2、4、12、24周)鲈鱼肉蛋白质特性的影响,通过测定鱼肉中盐溶性蛋白、巯基、羰基、Ca^(2+)-ATPase酶活含量、表面疏水性、内源性荧光光谱和蛋白质组成的变化,并采用双因素方差和相关性分析研究速冻方式和贮藏时间考察冻结后对鱼肉蛋白变性情况。结果表明:随冻藏时间的推移,盐溶性蛋白值呈下降趋势:平板组与液氮组,分别在冻藏末期最低与最高;巯基与Ca^(2+)-ATPase酶活值均呈先上升后下降的趋势;肌原纤维蛋白内源性荧光强度上升,产生蓝移现象,肌原纤维蛋白羰基与表面疏水性值显著性上升(P<0.05)。SDS-PAGE电泳结果表明,冻藏期间肌原纤维蛋白发生降解,而液氮组降温速率快,蛋白质降解程度越慢,平板组与其恰恰相反。液氮速冻形成冰晶体积与原料中水的分布相似,利于贮藏。相比较于液氮速冻,冷冻液速冻形成最大冰晶带时间长于液氮速冻,短于平板速冻,两者相差不大。双因素方差与指标间相关性分析表明,速冻方式对肌原纤维蛋白活性巯基、最大荧光强度影响显著(P<0.05),而冻藏时间是影响鲈鱼蛋白质的主因,冻藏时间越长,肌原纤维蛋白氨基酸侧链基团被氧化修饰,是造成蛋白质降解或聚集的主要因素。

In this paper,largemouth bass was used as raw material to study the effects of different cooling rates(liquid nitrogen quick freezing(1.81℃),freezing liquid quick freezing(0.15℃),flat plate quick freezing(0.14℃))in freezing storage(0,1,2,4,12,24 weeks),the influence of the physical and chemical properties of largemouth bass protein,by measuring the salt-soluble protein,sulfhydryl group,carbonyl group,Ca^(2+)-ATPase activity content,surface hydrophobicity,endogenous fluorescence spectrum and protein composition changes in the fish meat,and using double factor variance and correlation analysis study quick-freezing method and storage time to investigate the degeneration of fish protein after freezing.The results showed that with the passage of frozen storage time,the value of salt-soluble protein showed a downward trend:The plate group and liquid nitrogen group had the lowest and the highest at the end of the frozen storage,respectively;the activity values of sulfhydryl and Ca^(2+)-ATPase both increased first and then decreased.The endogenous fluorescence intensity of fibrin increased,resulting in a blue shift phenomenon,and the value of myofibrillar protein carbonyl and surface hydrophobicity increased significantly(P<0.05).The results of SDS-PAGE electrophoresis showed that myofibrillar protein was degraded during the freezing period,while the liquid nitrogen group had a faster cooling rate and a slower degree of protein degradation,while the plate group was the opposite.The volume of ice crystals formed by quick freezing of liquid nitrogen was similar to the distribution of water in the raw material,which was conducive to storage.Compared with liquid nitrogen quick freezing,the time for the formation of the maximum ice crystal zone in the quick freezing of liquid nitrogen was longer than that of liquid nitrogen quick freezing and shorter than that of flat quick freezing,and there was not much difference between the two.The correlation analysis between the two-factor variance and the indicators showed that the quick freezing method had a significant effect on the active sulfhydryl group and the maximum fluorescence intensity of myofibril protein(P<0.05).The freezing time was the main factor affecting the protein of the sea bass.The oxidative modification of amino acid side chain groups in myofibrillar protein was the main factor causing the degradation or aggregation of protein.