| China is the largest producer of freshwater fish. More than 20 million tons of freshwater fish were produced since 2008, and most of them were saled with fresh. Factors such as temperature and density could influence the suvival, physiology and biochemistry of fish, and further affect the meat quality and the economic benefit. For this reason, studies on the changes of fish and the conditions of transportation are essential to improve the technology of live-fish transportation and promote the market value. In this paper, blunt snout bream (Megalobrama amblycephala) was taken as experimental material, the effects of the low-temperature treatments in summer, winter and spring, the temporary culture time and the transportation density in summer on survival rate, physiology and biochemistry of meat, liver and serum were investigated. The results were as follows:1.The effects of low-temperature treatment in summer on survival rate, physiology and biochemistry of meat, liver and serum were studied. The water temperature decreased from 26℃to 7℃,9℃,11℃and 13℃with decreasing rate of 3℃/h. The results showed that the survival rate of blunt snout bream after 72h was 65% at 11℃, and the survival rate could remain 100% in 36h at 11℃. But the survival rates decreased sharply at 7℃,9℃and 13℃after holding 24h. The optimum temperature for keeping alive was 11℃. Compared to the control group, the contents of water, crude protein and adhesiveness, springiness and resilience had no significant change in the experiment groups (7℃,9℃,11℃and 13℃), but the water-holding capacity, pH value, hardness and the contents of crude fat, muscle glycogen and soluble protein had significant changed under low temperature. The contents of UREA, ALB, TP, CHOL, TG and activities of LDH-L, ALT had significant change in the low-temperature groups. In conclusion, the low tempreature had significant effects on the survival rate, biochemical characteristic and meat quality of blunt snout bream.2.The effects of low-temperature treatment in winter on survival rate, physiology and biochemistry of meat, liver and serum were studied. The water temperature decreased from 10℃to 1℃,3℃and 5℃with decreasing rate of 3℃/h. The results showed that the survival rate of blunt snout bream after holding 72h was 100%all at 1℃,3℃and 5℃. Compared to the normal temperature group, the content of crude protein and crude fat had no significant change in the low-temperature groups(1℃, 3℃and 5℃), while the content of water, pH value had significant effects under the three temperature treatments. The contents of UREA, TP, CHOL, TG and activities of LDH-L, ALT had no significant change in the low-temperature groups. Therefore, the normal temperature may be the suitable temperature in winter.3.The effects of low-temperature treatment in spring on survival rate, physiology and biochemistry of meat, liver and serum were studied. The water temperature decreased from 15℃to 1℃,3℃and 5℃with decreasing rate of 3℃/h. The results revealed that the highest survival rate of blunt snout bream after holding 72h was 100% at 5℃. The survival rates of blount snout bream after holding 72h were 97.50%, 92.50%,87.50% at 1℃,3℃and normal temperature, respectively. Under the low-temperature treatments (1℃,3℃and 5℃), the content of crude protein, crude fat and water-holding capacity had no significant change, but the hardness had significant increased with the temperature decreased. The contents of UREA had no significant changed at 5℃and 3℃, but increased at 1℃and normal temperature. The content of TP, CHOL, TG had no significant changed at 1℃,3℃and 5℃. Therefore the suitable temperature in spring was 5℃.4.The effects of temporary culture time on survival rate, physiology and biochemistry of meat, liver and serum were studied. The blunt snout bream were treated with different temporary culture time (24h,36h) at normal temperature, then the water temperature decreased to 11℃with decreasing rate of 3℃/h. The results showed that the average suvival rates were 100% in the groups of 24h and 36h but it was only 93.18% without holding culture. The content of water and water-holding capacity had no significant effects afer holding culture of 36h, while the content of crude fat and protein decreased significantly, the hardness decreased after holding culture, and increased with low temperature treatment. In the experiment group of 24h, the water-holding capacity and the contents of water, crude fat and crude protein had no significant effects, but hardness increased slightly. The contents of GLU, CHOL and the activities of LDH-L, ALT had significant decreased in the groups of 24h and 36h. So the temporary culture time of 24h had relatively less effects on the suvival rate, physiology and biochemistry of meat, liver and serum. Therefore, the temporary culture time of 24h was suitable to keeping alive for blunt snout bream.5. Effects of different transportation density (1:10,1:5,1:3) on the survival rate and meat quality and serum biochemical parameters of blunt snout bream were studied. The results showed that in density group 1:3, the average survival rate decerased greatly and was only 78.43% afer 72h. Under the density of 1:5 and 1:10, the average survival rate still remain 100% after 72h. No remarkable change on the contents of water, crude fat, muscle glycogen, soluble protein in the muscle between the 1:5 and 1:10 density except crude protein, and the change trend of the crude fat and liver glycogen contents were the same in the liver between the two groups. The levels of TG, CHOL and ALB had no remakable change in each density group. The level of UREA group decreased greatly with density decreased. The level of GLU decreased remakably in three groups. The level of TP decreased greatly in high density. Based on comprehensive consideration of survival rate, econnomic benefit, nutritive composition in muscle and stress response, the medium density 1:5 was the most suitable one in the three different densities in transportation. |
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