|Abstract: ||瓜子鱲（Girella punctata）屬高商業價值的新興養殖魚種，生化學組成特性之研究甚少，故擬分析飼料對其成長期間魚肉化學組成分之影響，比較野生與養殖魚肉化學組成之差異，並探討其貯藏期間各項鮮度指標與化學成分之變化，以了解其貯藏安定性。成長試驗期間瓜子鱲肥滿度與魚體體重具相關性，而肝體比則與體重之相關性小，各組別之pH 值、總核苷酸相關化合物與一般成分包括水分、粗蛋白和灰分含量與控制組差異甚小，但脂肪含量下降，而總游離胺基酸含量則有上升趨勢。養殖瓜子鱲之肥滿度與粗脂肪含量顯著高於野生魚，兩者肝體比無顯著差異；養殖瓜子鱲之總游離胺基酸含量為396 mg/100 g，遠較野生魚之189 mg/100 g高，野生魚個別胺基酸以牛磺酸 (Taurine, Tau)、甘胺酸 (Glycine, Gly)、丙胺酸 (Alanine, Ala)、離胺酸 (Lysine, Lys) 及脯胺酸 (Proline, Pro) 含量居多，其中 Tau 為主要胺基酸，而養殖魚個別胺基酸以 Tau、羥丁胺酸 (Threonine, Thr)、絲胺酸 (Serine, Ser)、Gly、Ala、Lys、His 及 Pro 含量居多，其中 Gly 為主要胺基酸；野生與養殖瓜子鱲之主要脂肪酸皆為棕櫚酸 (Palmitic acid, C16:0)、油酸 (Oleic acid, C18:1) 及 DHA (Docosahexaenoic acid, C22:6) ，而養殖魚含有較高比例之單元不飽和脂肪酸 (Monounsaturated fatty acid, MUFA)。呈味成分之肌苷酸 (Inosine 5’ –monophosphate, IMP) 為死後肌肉主要蓄積之核苷酸相關化合物，養殖瓜子鱲含量8.31 μmole/g，顯著高於野生魚之 4.95 μmole/g。將瓜子鱲肉貯藏於 25℃ 下，pH 值有逐漸上升之趨勢，而 4℃ 貯藏下則先下降再上升；25℃ 貯藏下氨含量隨著時間增加而逐漸上升，至 48 小時達 25.71 mg/100 g，於 4℃ 貯藏下氨含量變化不大；初始好氧性總生菌數 (Total plate count, TPC) 為 2.48 log CFU/g，隨著貯藏時間增加而逐漸上升，於 25℃ 儲藏至24 小時達 6.73 log CFU/g，超出限量標準 (6.48 log CFU/g)，4℃貯藏 12 天則達 4.04 log CFU/g，則未超過限量標準；起始揮發性鹽基態氮 (Volatile basic nitrogen, VBN) 含量為 7.64 mg/100 g，隨著時間增加而上升，於 25℃ 儲藏至16 小時達 33.62 mg/100 g，4℃貯藏至第 9 天則達 53.03 mg/100 g，超過限量標準之25 mg/100 g；於 25℃ 貯藏至 8小時 K 值急遽上升達 84.95%，4℃ 貯藏第 3 天達 65.22% ，已超過 60%，鮮度不佳。氨含量、VBN、Hypoxanthine 及 K 值皆隨貯藏時間增加而上升，可作為瓜子鱲肉之鮮度指標，依感官檢測、TPC與 VBN 含量可判斷瓜子鱲肉於 25℃ 貯藏期限約為 8 小時、4℃ 約為 6 天。|
Black fish (Girella punctata) is an important newly culutured fish with high economic value, but biochemical compositions remain unknown. Therefore, this study was designed to investigate the effect of fermented soybean as feeding source on biochemical compositions of fish meat, the difference in compositions between wild and cultured black fish, and the changes in compositions and fressness indicators during storage. The condition factor showed a positive correlation with fish weight during growth, but there was no significant correlation between hepatosomatic index and body weight. No significant difference in pH value, nucleotide-related compounds (NRC), moisture, ash and crude protein were found between cultured fish fed with soybean and control group during growth. However, cultured fish had lower crude fat than control group, but had higher free amino acids (FAAs). The condition factor of wild blackfish was significantly lower than that of cultured fish. However, the cultured blackfish had higher fat content than wild fish. There were no significant differences in moisture, protein and ash contents between cultured and wild fish. The total FAAs content in cultured blackfish were significantly higher than those of wild fish. Taurine was the most prominent FAA in wild balckfish, while glycine was predominant in cultured fish. Results suggest that soybean meal as feeding source for fish could increase the content of total FAAs. Cultured blackfish also has higher content of monounsaturated fatty acids. The major NRC in the muscle was inosine monophosphate (IMP) in both wild and cultured blackfish. Moreover, IMP in cultured backfish was significantly higer than wild fish. The initial total plate count (TPC) was 2.48 log CFU/g, and increased with storage time. TPC increased to 6.73 CFU/g during storage at 25℃ for 24 hours, and 4.04 CFU/g at 4℃ for 12 days. The value of volatile basic nitrogen (VBN) increased with storage time, and exceeded the limit value of 25 mg/100 g at 25℃ storage for 16 hours and 4℃ for 9 days, respectively. In addition, ammonia and K value increased with storage time. According to organoleptic evaluation, TPC and VBN value, the shelf-life of wild blackfish was 8 hours at 25℃ storage and 6 days at 4℃ storage, respectively.