Studies on the variations in meat property of fish within species

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To find out the bilogical factors affecting the variation in the meat property of fish within species, the effects of spawning, starvation, diet and water temperature on the proximate composition, protein commposition, gel-forming potential and modori(thermal gel degradation at 60゜C)-inducing property of lizardfish (Saurida elongata) and tilapia(Sarotherodon niloticus) meat were examined.In the case of lizardfish caught from Seto Inland Sea, myofibrillar protein content of the muscle decreased severely during spawning period, from June to July,accompanying lowering in the gel-forming potential and a increasing in the modori-inducing property. After spawning, however,in spite of rapid recovery of the myofibrillar proteins, the gel-forming potential did not restore until October due to prolonged high modori-inducing property after spawning. Long term starvation also caused to decrease the gelling potential and increase the modoriinducing property of tilapia muscle. Myofibrillar proteins reduced remarkablly during starvation and recovered after refeeding. Among the three kinds of diet, fishmeal, krill meal and phytoplankton, phytoplankton was found to be best for temperature between 20゜C and 30゜C seemed to have practically no influence on not only gel-forming potential but also modori-inducing property of muscle of tilapia.From the results, spawning and starvation, in which fish is forced to utilize myofibrillar proteins as an energy source, are found to be major causes of the variation of meat property within species. Diet also seems to be a minor ractor, while water temperature does not play an important role in the variation of fish meat property.