Effects Of Treatment Before Transportation On Biochemical Properties And Meat Qaulities Of Crucian Carp

There are 90%freshwater fish that are sold lively in China due to some reasons, such as consumption habit,backward development of processing and preservation industry.Transportation of live fish is the key problem which should be solved during transferring aquatic products from farms to markets.Stress responses of fishes are caused by environmental factors,which results in physiologic and biochemical changes of fishes, and finally affected the meat quality.The effects of low-temperature treatment,chemical treatment,treatment combined electrical stunning with low temperature on biochemical indices and meat quality of crucian were investigated,based on the study on the optimum of low-temperature treatment,chemical treatment,treatment combined electrical stunning with low temperature.The results were as follows:1.The effects of low-temperature treatment on biochemical characteristic and meat quality were studied.The results showed that the ammonia-N excretion increased with increasing temperature,and was significantly higher at 20.0℃than three other temperatures(3.5,6.5 and 9.5℃).The survival rates of crucian after holding 5 days were 85.0%,100.0%,94.7%and 75.0%at 3.5,6.5,9.5 and 20.0℃respectively.The optimum temperature for keeping alive was 6.5℃.The contents of LDH,AST,glucose and cortical in the experiment groups(3.5,6.5 and 9.5℃) decreased after holding 5 days, whereas those at 20℃increased.The low-temperature treatment had no significant effects on meat elasticity and the content of crude protein,but had significant effects on water-holding capacity,cohesiveness,resilience,pH value,the contents of soluble protein and fat.The low-temperature treatment had significant effects on survival rate, biochemical characteristic and meat quality,so optimal temperature was 6.5℃for keeping alive during transportation.2.The effects of chemical treatment on biochemical characteristic and meat quality were studied.The effects of MS-222 anesthetic concentration,water temperature and fish density on cortical,glucose,LDH and AST were significant or extremely significant. Cortical,glucose,LDH and AST of the control group were higher than original level. AST of the anesthesia group were significantly higher than original level,but cortical, glucose and LDH of the anesthesia group showed the different trends.The effects of MS-222 anesthetic concentration,water temperature and fish density on pH value, holding-water capability,crude fat,crude protein,soluble protein,whiteness and hardness were significant or extremely significant.When crucian carp was holded at 30mg/L,MS-222 at 15℃with 1:6 fish-water ratio,its survival rate was the highest with lower stress degree and better meat quality.3.The effects of electrical stunning on biochemical characteristics and meat quality were studied.The effects of voltage and time of electrical stunning on cortical,glucose, LDH and AST were extremely significant.Cortical,glucose,LDH and AST increased after electrical stunning,which were caused by stress response.The pH value of the electrical stunning group was significantly lower than that of the control group.Voltage and time of electrical stunning significantly influnced holding-water capability,crude protein,pH value,soluble protein,crude fat,whiteness,hardness and resilience,but had no visible effects on elasticity and adhesiveness.When crucian carp was stunned at 20V for 6min,the stress response was less,with higher retention of nutrition.4.The effects of electrical stunning and low-temperature treatment on biochemical characteristic and meat quality were studied.Crucian carp were directly reared at 6.5℃after stunning with different voltages and time.Cortical,glucose,LDH and AST of the electrical stunning group were lower than those of the control group.The ammonia-N excretion remarkably decreased after electrical stunning.Additionally the ammonia-N excretion increased with increasing voltage and time in the later period.Voltage and time of electrical stunning significantly crude protein,pH value,soluble protein,crude fat, whiteness,hardness,elasticity,adhesiveness and resilience.When crucian carp was stunned at 20V for 4rain or 6min,its survival rate after holding 5 days at 6.5℃were the highest(91.5%),which was 10%higher than that of the control group,meanwhile,its holding-water capability,crude protein,soluble protein,crude fat,elasticity and resilience were higher than that of the control group.