Improvement of Flavor of Cultured Oyster

牡蛎在日本和其他许多国家都是受欢迎的海鲜之一。然而，欧洲牡蛎(Ostrea Edulis)在日本的生产和消费非常有限。为了增加养殖牡蛎的消耗量，本研究旨在通过投喂浮游植物或配方食品来改善其风味。分别以纤细角毛藻(C.G组)和新月菱形藻(Nitzschia cllosterium N.C)两种硅藻、球等鞭金藻(Isochrysis galbana，I.G组)和配合饲料(RL组，简称RL组)两种硅藻为饲料，在水箱中饲养4组欧洲平贝，共饲养30d。结果：1.对照组留在海里。在可食用部分的感官测试中，许多小组成员回答说，I.G组在甜度、鲜味和口感上优于对照组，表明前者比后者更容易被接受。C.G、N.C和RL组的质地、气味和盐度均低于对照组。3.4个试验组的糖原含量均显著低于对照组。I.G组富含牛磺酸、甘氨酸和谷氨酸。丙氨酸和甘氨酸在‘C.G组和N.C组明显较差。饱和、单不饱和和多不饱和(PUFA)脂肪酸分别占总脂肪酸的32~34%、15~21%、47~52%。RL组PUFA百分比最低，n-3系列脂肪酸水平低于其他两组，而n-6系列脂肪酸水平高于其他两组。柱塞法测定的消化器官韧性，正常对照组为42g/mm~2，其他组为27~29g/mm~2。5组消化器官蛋白质组成中，水溶组分为35-53%，盐溶组分为21-33%，碱溶组分为18-26%，不溶组为5-6%。质构与蛋白质组成之间没有相关性。

Oyster is one of Popular seafoods in Japan as well as in many other countries. However, the Production and consumption of the European Flat oyster, Ostrea edulis, are very Limited in Japan. For the purpose of increasing the consumption of the cultured oystes, the present research aimed at the improvement of its Flavor by feeding phytoplankton or formula food.1. Four groups of European flat oyster were reared on each of two species of diatom, Chaetoceros gracilis (C.g group) and Nitzschia closterium N.c group), a haptophyte, Isochrysis galbana (I.g group) and a formula feed (RL group) for 30 days in tanks. The control group was kept in the sea.2. In the sensory tests of edible parts, many panelists answered that the I.g group was better than the control group in sweetness, umami and astrigency, indicating that the former was more acceptable than the latter. The C.g, N.c and Rl groups were judged to be inferior to the control group in texture, odor and saltiness.3.The contents of glycogen in the 4 test groups were considerably lower than that of the control group. I.g group was rich in taurine, glycine and glutamic acid. Alanine and glycine were markedly poor in the'C.g and N.c groups.4. The levels of saturated, monounsaturated and polyunsaturated (PUFA) fatty acids were 32-34%, 15-21%, 47-52% of total fatty acids, respectively, in the 5 groups. The percentage of PUFA was the lowest in the Rl group, which showed also lower level of n-3 series fatty acids but higher n-6 ones than the other groups.5. The toughness of digestive organs as measured with a plunger was 42 g/mm^2 for the N.c group and 27-29 g/mm^2 for the other groups. As for the protein composition of digestive organs of the 5 groups, the water-soluble, salt-soluble, alkali-soluble and insoluble fractions were 35-53%, 21-33%, 18-26% and 5-6%, respectively. No correlation was observed between the texture and protein composition.