養殖魚の筋肉中に出現する黒い筋の除去に関する研究 Ｉ 養殖マダイ筋肉中の黒い筋の軽減と体色改善について

Abstract

The flesh quality of cultured red sea bream is distinguished from wild red sea bream by the body color and black lines in the muscle. By histological observation, the part where black lines appear and their properties were clarified by histochemical analysis. Furthermore, effects of sun-shade in rearing under different shade rates were examined for the purpose of protecting the surface of the body from melanism and removing black lines from the muscle. Black lines were observed along the periphery of the blood vessel, while dark green stain-ing with ferric ferricyanide and decoloration with 40% peracetic acid showed that melanin was contained in them. Unlike melanophores in the cutis, those in the black lines didn't respond either to KCl or to NaCl. The brightness (L value) of the body color of the sun-shaded specimen determined by using a color meter evened up with that of wild red sea bream, and the density of black lines decreased from 17 day-sun-shade on a rate of more than 90% shade. The wild red sea bream maintained body color during the experimental period by sun-shade. Of ultraviolet and visible rays, shading of the later was more effective in the removal of black lines. It has been definitely shown by these results that sun-shade of more than 17 days and a rate of 90% rate is effective in the improvement of flesh quality of cultured red sea bream.