Studies on freshness of trawl catches - VI. The influence of rearing water temperature on the relative thermostability of myofibrillar Ca2+-ATPase and on the lowering speed of freshness in carp.

Abstract

The effects of habitat temperatures on the thermostability of myofibrillar ATPase, resolution characteristics of ATP related compounds, and lowering speeds in freshness of fish muscle were experimentally studied using carps reared at 10°C (group L) and 30°C (group H) for different lengths of period. The rate constants (KD) of inactivation of myofibrillar Ca2+-ATPase increased for group L fish, and decreased for group H fish, with the extension of the rearing period. Either of the decreasing rate of ATP+ADP+AMP (%/h), increasing rate of K values, de-creasing rate of glycogen, increasing rate of lactic acid, and lowering speed of pH in fish muscle kept at 32°C after killing was much greater for group L than for group H. The results of the present, combined with those obtained previously for fishes from various localities of different habitat temperatures, convinced us that the thermostability of myofibrillar ATPase and lowering speeds in freshness of fish muscle are markedly affected by the habitat temperatures. The results also indicated that, in fishes as poikilotherms, the relative activities of a series of enzymes participating in the degradation of ATP related compounds and in the metabolism of glycogen become higher with a lower habitat temperature as an adaptation for an effective generation of energy at a low temperature.