Studies on the Improvement of Flesh Quality and Integumentary Color of Cultured Striped Jack Pseudocaranx dentex

为改善养殖齿纹夜蛾的色泽、口感和质地的品质，进行了多项试验，试验一结果表明，投喂螺旋藻是非常有效的。添加10%水平的螺旋藻降低了背部肌肉、肝脏和内脏的脂肪水平，不仅改善了肉质的色泽和质地，而且改善了腹肌的口感，达5%的显著水平。投喂含藻量为5%或10%的饲料的鱼的皮肤颜色在背部变成彩虹绿灰色，并在侧线附近出现一条特征黄带，而不含藻类或切碎的生沙丁鱼的对照组鱼的皮肤呈现深灰色。黄素、叶黄素和玉米黄素占背珠被中类胡萝卜素的95%以上(0.28-1.5 mg/100g组织)，且随着螺旋藻的添加，类胡萝卜素的含量均增加。在最终的实验中，螺旋藻被分离出丙酮、甲醇、水和乙醚的可溶性部分和极脂部分，每个部分都被用来喂鱼以鉴定藻类中的有效成分。结果表明，甲醇可溶或极性脂肪组分中的γ-亚麻酸(GLA)能有效改善肉质，降低肌肉和肝脏中的脂肪含量。因此，在实践中，建议在水产饲料中每100个干颗粒添加约100毫克GLA。

Various trials were conducted in order to improve the quality of cultured striped jack, Pseudocaranx dentex, in terms of pigmentation of skin, taste and texture.The results of the first experiment showed that feeding of Spirulina was very effective for this purpose. The supplementation of Spirulina at 10% level depressed the lipid levels of the dorsal muscle, liver and viscera, and improved not only the integumentary color and texture, but also the taste ofventral muscle at 5% significance. The skin color of fish fed diets containing the alga at 5% or 10% became iridescent greenish gray at the back with a characteristic yellow band near the lateral line, whereas those on the control diet without the alga or minced raw sardine exhibited dark gray. The three yellow components - tunaxanthin, lutein and zeaxanthin - constituted more than 95% of the carotenoids (0.28-1.5 mg/100g tissue) in the dorsal integuments and all of them increased on supplementation of Spirulina. These results were also confirmed using a newly developed soft-dry pellet which high palatability and acceptability to striped jack.In the final experiment Spirulina was separated into the acetone, methanol, water and ethyl ether soluble fractions and polar lipid fraction, whereupon each was fed to fish to identify the effective component in the alga. The results have shown that gamma linolenic acid (GLA) in the methanol soluble or polar lipid fraction was effective for improvement of flesh quality, reducing the lipid content in muscle and liver. Thus, in practice, it is recommended that aquatic diets could be fortified with about 100 mg GLA per 100 dry pellet.