Effect of retention conditions on quality of frozen and fresh bighead carp(Aristichthys nobilis)

It was aimed at studying quality changes in bighead carp muscle. The p H,sensory evaluation,TVB-N,shear force,drip loss and microstructures were analyzed to evaluate the effects of residence time(1~24 h,1~8 h)and retention temperature( 4, 20 ℃) on the quality of steak. The results showed that as residence time extended,the p H decreased rapidly before turning point,which was 8 h at 4 ℃ and 4 h at 20 ℃,after that it decreased slowly or increased slightly. Sensory evaluation,shear force declined while TVB-N value rose gradually. Furthermore,all indexes except p H,sensory evaluation and shear force changed more rapidly after turning point. The microstructure was altered obviously as residence time extended,as indicated by increased space between fibers,loose structure,and so on. Drip loss of frozen fish increased with the increasing residence time. The same trends of other indexes appeared in frozen fish along with those unfrozen,and more decomposition of muscle fibers was observed. In order to obtain high-quality frozen fish,residence time should be less than 8 h(4 ℃) or 4 h(20 ℃).