The Study Of Different Freezing Temperature And Repeated Freeze-thaw On Storage Quality Of Prawn

In this paper, the prawn quality changes were studied under different freezing storage temperature and freeze-thaw cycles. According to the data, we hope to provide theoretical reference for storage time and quality change under different temperature, also the effect of freeze-thaw cycle. It will provide technical guidance to improve the quality of frozen prawn.In this study, sensory index, volatile basic nitrogen (TVB-N), protein content, thiobarbituric acid (TBARS) value, pH, and thawing drip loss were tested to analyze the quality change of prawn stored at -5℃,-10℃,-15℃ and -20℃ for 180d. The frozen shrimps were repeated freeze-thaw for 6 times while choosing the frozen temperature -20℃, sensory and associated physi-chemical indicators of prawns were measured each time after thawing. The contrast between freezing-thawing circulation and control group was made to discuss the effect of temperature fluctuations and repeated freeze-thaw on the quality change of prawns(1) With the extension of storage time, the sensory quality and protein content of Chinese prawn declined, TVB-N, TBARS and thawing loss rate grew obviously, pH showed fluctuant trends. According to the sensory score and physi-chemical indicators of the four temperature,-20℃ and -15℃ were better than -10℃ and -5℃ to keep the quality of prawn and relief its blacken. While stored at -20℃, the protein content of the prawn and TBARS were significant superior to that of stored at -15℃,-10℃,-5℃. Thus,-20℃ was suitable for the storage of frozen prawns.(2) According to experiments, protein content rose slightly during the frozen storage of shrimp meat. TVB-N, TBARS and thawing loss rate increased obviously and pH fluctuated. But TVB-N, TBARS and thawing loss rate were less than directly frozen prawns group, and due to the lack of protection of shrimp shell and in the same storage time shrimp water loss rate is greater than the protein decomposition rate, the relative content of protein with the increase of small amplitude. Thus, the quality change of the prawn shrimp meat was smaller, which was more suitable for frozen storage. But the prawn shrimp meat already belongs to semi-finished products and the processing characteristics of late slightly lost in the frozen prawns directly, so which type to choose for frozen storage need to be based on specific needs.(3) According to the sensory evaluation and physi-chemical analysis, prawns sensory quality and protein content of freeze-thaw cycles group declined significantly than the control group, while TVB-N, TBARS and thawing loss rate was higher. However,, pH fluctuated slightly. Therefore, repeated freeze-thaw or temperature fluctuations will shorten the storage times, reducing nutritional value and quality. So the stability of temperature during freezing storage is important to guarantee the quality of the prawn.