调制鱼冷藏过程导致熟化后鱼肉质构劣变的机理

The markets of chilled prepared foods are developing rapidly as life pace becomes faster and pressure gets bigger. The texture quality of cooked fish will deteriorate as its stored time prolonging in shelf life. Based on this problem, the correlation between the change of protein during shelf life of chilled prepared fish and texture quality of the resulting cooked fish was researched in this project, with the purpose of establishing the theoretical foundation for inventing preservation techniques of chilled prepared fish in shelf life. The change of texture quality and protein in chilled prepared fish during its shelf life were studied firstly. Then the change of texture quality and protein in fish during heating and cooked fish also were studied. The index related to protein influenced the formation of texture quality significantly during heating were screened by correlation analysis. The changing process of these index in fish via different stored time and their mechanism of influence to the formation of texture quality during the overall process from storage of fish to cooked fish were studied, as well as the difference caused by different stored time of chilled prepared fish was analyzed. Then the source of the difference, viewed from the change of protein in chilled prepared fish during storage, also was analyzed. Based on the previous studies, the mechanism on deterioration of texture quality of cooked fish caused by stored time extension of chilled prepared fish during its shelf life will be uncovered.

随着人们的生活节奏加快和压力增大，冷藏调制食品市场发展迅速。冷藏调制鱼在货架期存储过程中，随时间的延长，相应熟化鱼肉质构品质产生劣变，本项目基于这一实际问题，重点研究冷藏调制鱼货架期存储过程中蛋白质变化影响熟化后鱼肉质构品质的机理，旨在为冷藏调制鱼制品货架期内保鲜技术的研发奠定理论基础。项目首先研究调制鱼冷藏过程中质构特性和蛋白指标的变化规律，再研究熟化过程中以及熟化后不同冷藏时间调制鱼质构特性和蛋白指标的变化规律，进而通过相关性分析筛选出不同冷藏时间调制鱼熟化过程中，显著影响鱼肉质构特性形成的蛋白指标。在此基础上，分析不同冷藏时间调制鱼在存储、熟化以及熟化后这一动态过程中显著影响质构品质的蛋白指标的演化过程及其影响熟化鱼肉质构品质形成的机制，比较其中差异，并从调制鱼冷藏过程中蛋白指标变化的角度分析差异产生的根源，最终解析货架期内冷藏调制鱼存储导致鱼肉熟化处理后质构劣变机理。

本研究证明对于货架期贮藏前期（1-3天）的生鱼肉来说，随着贮藏时间延长，维持和调节肌肉结构的肌联蛋白逐渐降解，伴随着肌节中I-带长度的增加，同时肌联蛋白的降解使得肌原纤维蛋白二级结构的稳定性下降，色氨酸残基逐渐暴露，蛋白三级结构逐渐展开。随着贮藏时间的进一步延长，生鱼肉中肌联蛋白和伴肌动蛋白几乎完全降解，肌间线蛋白和原肌球蛋白也在逐渐降解，导致肌节中N2线被破坏的程度加大，Z-线变得模糊，同时肌联蛋白等的降解使得蛋白结构的稳定性下降，蛋白二级和三级结构更容易被破坏。. 热处理过程中，随着贮藏时间的延长，肌联蛋白和伴肌动蛋白降解程度明显增加,贮藏3天的熟鱼肉中已经完全降解，肌节结构被破坏，蛋白二级和三级结构在加热过程中进一步展开，色氨酸和酪氨酸残基逐渐由暴露转向包埋，导致其与氢键的作用减弱，α-螺旋逐渐向无规卷曲转化，蛋白结构趋向于无序化，从而使鱼肉在加热后期其强结合水含量上升，最终造成鱼肉的内聚性和蒸煮损失率增加，剪切力下降，降低鱼肉的食用品质。货架期贮藏后期的生鱼肉在加热过程中，结构蛋白的降解速度明显加快，肌联蛋白和伴肌动蛋白已完全降解，这不仅加剧了肌节结构和蛋白结构的被破坏程度，也使得蛋白网络结构疏松化，保水性下降，从而造成不易流动水的流动性上升，自由水含量下降，造成鱼肉的硬度和应力下降，内聚性和蒸煮损失率上升，鱼肉的食用品质劣变。..