淡水养殖鱼类死后生化变化及其对鲜度质量的影响

本文采用不同致死方法研究究死前不同生理状态对死后ATP及其相关物质的生化变化，并结合编、鲢、草鱼的部分K值测定结果，考察了鱼体在僵硬前期与全僵期的鲜度质量变化。测定结果表明：（1）活杀、挣扎死和半死的精，死后最初ATP和乳酸含量与达到全僵的时间直接相关，死前肌肉ATP和糖原消耗的有无和程度是决定其死后达到全僵时间长短与活杀效果大小的根本因素，因而对改进保鲜技术具有重要指导意义。（2）编死后达到全僵的时间与IMP达到最高值的时间一致，随后IMP缓慢下降，HxR及K值缓慢上升，达到解僵前的IMP仍保持在较高的水平。（3）不同季节的镛、鲢和草鱼死后达到全僵时的K值均基本保持在20％以内的高鲜度范围，但达到解僵时的K值，仅在解僵时间短的夏季和春季可能保持在20％以内，对在解僵时间长的秋季和冬季，均超过20％，甚至接近40％．表明鲜度质量逐渐下降。

POST-MORTEM BIOCHEMICAL CHANGES AND THEIR EFFECT ON FRESHNESS OF CULTURED FRESHWATER FISH

Effect of different physiological states of cultured bighead carp before deathon its post-mortem changes of ATP and its related compounds in the duration of rigor mortiswas studied in this paper in association with its change of freshness measured by K valueduring this period. The results were summarized as follows:(1)The time from death to full rigor (Tr) was directly dependent on the initial contentof ATP and lactic acid (la) after death. The degree of depletion of ATP and glycogen beforedeath was the decisive factor for the Tr, so it is important for the improvement of freshnesskeeping technique.(2)Along with the fish muscle reached full-rigor state, the IMP concentration (IMP)increased to the highest level, then decreased slowly, and kept at a higher level before theresolution of rigor mortis beginning. On the other hand, K value ascended accompanyingwith HxR and Hx accumulation.(3) For bighead, silver carp and grass carp in different seasons, when the musclereached full-rigor state, the K value was less than 20% which means high freshness of fish.But when it reached rigor-resolution, the K value that showed a degradation of freshness offish might be kept within 20% only in the spring or summer season, when the time reachingrigor-resolution was much shorter. As in autumn or winter, the K value would be more than20% even 40% when the time reaching rigor-resolution became longer.