Study On Freezing Processing And Quality Improvement Technology Of Bighead Carp(Aristichthys Nobilis) Heads

Bighead carp(Aristichthys nobilis) is one of the important freshwater fish species aquaculture in China. Bighead carp head has delicious taste and rich nutrition, which make them popular. As by-product of fillet or other products, the head delivery to market can hardly maintain the fresh state. To extend the shelf-life and preserve the quality of fishery products, freezing and frozen have been employed. It’s necessary to comprehend the post-mortem changes of bighead carp; learning sensory quality, physical and chemical characters as well as texture changes are affected by different treatments. Improving the quality of bighead carp head during frozen storage has a positive effect on frozen processed bighead carp head. This paper focused on residence conditions, freezing method and frozen storage, which influence the frozen fishery quality. Quality improved was hoped during long-term storage, so as to provide the basis for frozen processing of bighead carp head.Effects of residence conditions on the quality of bighead carp frozen were first studied. The results showed that as residence time extended, the p H decreased rapidly before turning point, which is 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. The microstructure changed obviously as residence time extended, indicated by increased space between fibers, loose structure, and so on. Furthermore, all indexes except p H changed more rapidly after turning point. 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 were observed. In order to obtain high-quality frozen fish, residence time should be less than 8 h(4℃) or 4 h(20℃).Quality changes(texture and sensory properties, water holding capacity(WHC), denaturation of protein and lipid oxidation) in bighead carp head treated with different methods were examined during short-term frozen storage. It showed that the rate of immersion freezing(IF) was almost 6 times as static air freezing(SF) and air-blast freezing(AF). Treated by immersion freezing, better quality could be observed, especially in the first week. Microstructure showed that muscle cells shape were irregular and fiber atrophy occurred in those treated by SF and AF. The decline of WHC and texture were accompanied by an increase in lipid oxidation and protein denaturation during frozen storage. Small differences existed between frozen and fresh samples in first week, while substantial sensory changed after 10 days, although there were no significant changes on other indicators. IF had less negative impact on the quality of frozen bighead carp, but it couldn’t maintain the original quality in the long-term storage.The quality of frozen bighead carp was improved by light-salt treated. Considering the freezing point, water content and changes of amino nitrogen, organic acids, 6% Na Cl(w/w) curing 3h was selected. The salted samples had better sensory quality and texture properties than those unsalted at the same frozen time. Although whiteness decreased and lipid oxidation increased of salted samples, this won’t affect the overall acceptability. The quality(sensory score and texture properties) of frozen bighead carp could be improved by light-salted treatment along with high-quality life extended effectively.