|Abstract: ||龍膽石斑 (Epinephelus lanceolatus) 為台灣養殖漁業中重要的高經濟價值魚類，本研究目的在建立龍膽石斑各部位化學及營養呈味成分之資料，並藉由貯藏試驗了解其貯存安定性。龍膽石斑魚肉蛋白質含量約為 20%，脂肪含量約介於 3.9-6.4%，較大部份石斑魚類高。各組織部位中以中骨之脂肪含量最高 (12.5-14.2%)，其 pH 值亦較其他部位高。呈味成分之肌苷酸 (inosine monophosphate, IMP) 為魚肉中主要蓄積之核苷酸化合物，魚皮則以腺苷酸 (adenosine monophosphate, AMP) 為主，中骨之核苷酸化合物含量較低。牛磺酸 (taurine, Tau) 為龍膽石斑主要游離胺基酸，其次為精胺酸 (arginine, Arg)、離胺酸 (lysine, Lys) 及甘胺酸 (glycine, Gly)，各組織部位中以下巴肉之牛磺酸含量較高，中骨及魚皮含量較低。龍膽石斑亦富含胜肽類胺基酸，可食肉部位含量介於 660-1390 mg/100 g 之間。脂肪酸組成方面，魚肉富含 C16:0、C18:0、C18:1 及 ω-3 高度不飽和脂肪酸 C20:5 (eicosapentaenoic, EPA) 與 C22:6 (decosahexaenoic acid, DHA)。 龍膽石斑肉於 25℃貯藏期間，pH 值先升後降，7℃冷藏樣品則先降後升。25℃貯藏之魚肉氨含量隨貯藏時間逐漸增加，貯藏至第 16 小時揮發性鹽基態氮 (VBN) 已達 57 mg/100 g，但於 7℃貯藏 9 天，VBN 仍低於衛生標準值之 25 mg/100 g。三甲胺 (TMA) 含量於 7℃貯藏期間變化不大，但在 25℃貯藏期間急遽增加。在 ATP 相關化合物方面，7℃貯藏樣品之 IMP 緩慢降解形成肌苷 (HxR) 及次黃嘌呤 (Hx)，但 25℃樣品之 IMP 則有急遽下降之趨勢，且以 Hx 為主要蓄積物。K 值於 7℃貯藏時緩慢增加，而 25℃貯藏 8 小時後即急遽增加。游離胺基酸於 7℃貯藏期間變化不大，25℃貯藏期間有先減後增之趨勢。總生菌數在 7℃和 25℃分別貯藏 6 天與 16 小時皆已超過魚介類總生菌數之衛生標準值 3 × 106 CFU/g，並開始產生腐臭味。龍膽石斑 7℃貯藏需於 6 天內食用，而 25℃下貯藏則勿超過 8 小時，總生菌數、VBN 及 K 值可作為貯藏期間之鮮度指標。|
King grouper (Epinephelus lanceolatus) is an important cultured fish with high economic value in Taiwan. This research aims to understand the chemical compositions, nutrition and flavor ingredients of various tissues of king grouper and their changes during storage. The protein content of the muscle is about 20%; and the fat ranged from 3.9-6.4%, higher than most of other groupers. The bone showed the highest value in fat (12.5-14.2%) and pH value. The major nucleotide-related compound in the tissue was inosine monophosphate (IMP), while that in the skin was adenosine monophosphate (AMP). Lower value of nucleotide-related compound was found in the bone. The predominant free amino acid (FAA) in the tissues was taurine (Tau), followed by arginine (Arg), lysine (Lys) and glycine (Gly). The content of taurine was higher in chin meat, and lower in bone and skin. The total amount of peptide in the tissues ranged from 660-1,390 mg/100 g. The muscle was rich in C16:0, C18:0, C18:1 and ω-3 highly unsaturated fatty acid EPA and DHA. When stored at 25℃, the pH value of the muscle increased and then decreased. On the other hand, the pH value decreased and then increased at 7℃. The ammonia content increased gradually with storage time. After storage for 16 hours, volatile basic nitrogen (VBN) reached 57 mg/100 g. When stored at 7℃ for 9 days, VBN did not exceed the limited value of 25 mg/100 g. No significant change in the content of trimethylamine (TMA) was found during storage at 7℃, but it increased in the beginning and decreased in the later stage during storage at 25℃. When storage at 7℃, the decomposition of IMP resulted in the accumulation of inosine (HxR) and hypoxanthine (Hx), but it decreased dramatically at 25℃ and Hx became the dominant compounds. K value increased gradually during storage at 7℃, but it increased dramatically at 25℃ after storage for 8 hours. The total amount of FAA slightly changed during storage at 7℃, but it decreased and then increased at 25℃. The total plate count exceeded the limited value of 3 × 106 CFU/g at 6th days and 16th hours for samples stored at 7℃and 25℃. The shelf-life of king grouper meat were 6 days and 8 hours during storage at 7℃ and 25℃, respectively. The total plate count, VBN, and K value can be used as freshness indicators for king grouper during storage.