|Abstract: ||目前市售一夜干水產品 (lightly salted and dried fish products) 之品質衛生資料闕如，本研究針對市售一夜干產品進行化學組成、衛生品質及呈味成分之調查和分析；並探討鯖魚一夜干產品於不同溫度下貯藏之品質變化。研究結果顯示，20 種一夜干水產品水分含量介於 55.3~77.5% 之間、蛋白質 15.7~22.6%、脂肪 1.0~23.4%、灰分 1.0~2.5%，產品之魚種不同，一般成分差異大，鯖魚與香魚之脂肪含量較高。分析六種魚種產品之核苷酸及其相關化合物，午魚、鯖魚、竹筴魚、香魚 IMP 含量介於 5.82~6.41 mg/100 g。一夜干之游離胺基酸含量，以組胺酸、牛磺酸、丙胺酸、甘胺酸等較多，鯖魚之組胺酸含量最高，竹筴魚次之，麩胺酸含量皆低，顯示產品未添加味精。一夜干之 pH 值介於 5.78~6.8 之間，鯖魚產品之 pH 值較低，所有產品之揮發性鹽基態氮 (volatile basic nitrogen, VBN) 皆低於食品衛生標準 (25 mg/100 g )，總生菌數亦符合冷凍食用魚介類之標準含量 3 × 106 log CFU/ g 以下，20 件產品皆未檢驗出大腸桿菌。 鯖魚一夜干之 VBN、三甲基胺 (trimethylamine nitrogen, TMA-N)、總生菌數、pH 值與灰分較原料鯖魚高。生鮮鯖魚在 7o℃ 貯藏至第 6 天有腥臭味產生，而在 25℃ 貯藏至第 32 小時已達腐敗階段；鯖魚一夜干在 7℃ 貯藏第6天有腥臭味產生，在 25℃ 貯藏第 32 小時已腐敗。生鮮鯖魚與一夜干產品於 7℃ 貯藏至第 6 天已超過總生菌數限量標準；25℃ 貯藏期間，生鮮鯖魚與一夜干於第 8 小時超過標準。生鮮鯖魚在 7℃ 與 25℃ 貯藏期間，VBN 值在第 6 天及第32 小時含量超過限量；鯖魚一夜干在 7℃ 貯藏第 6 天超過標準，25℃ 貯藏32 小時內仍未超過初期腐敗限定。TMA-N 含量於貯藏期間隨時間而增加，而7℃ 貯藏期間上升幅度較 25℃ 緩慢。於 7℃ 貯藏第 6 天核苷酸相關化合物便急速降解為次黃嘌呤，K 值上升幅度較為緩慢，生鮮鯖魚於 25℃ 貯藏 8 小時與鯖魚一夜干貯藏 16 小時後，次黃嘌呤急遽增加，K 值迅速上升。綜合以上鮮度衛生品質指標，鯖魚一夜干之貯藏安定性近似生鮮鯖魚，兩者之 7℃ 貯藏期限為 3 天；25℃ 貯藏期限為 8 小時。|
Little information regarding the quality and sanitation of commercial lightly salted and dried fish products is available. This study was to investigate the biochemical characteristics, sanitation indicators and storage stability of commercial products. The fresh fish was analyzed for comparison of lightly salted and dried fish products. Changes in the quality of products during storage at different temperatures were also studied. The contents of moisture, protein, lipid and ash of commercial lightly salted and dried fish products were 55.3~77.5%, 15.7~22.6%, 1.0~23.4%, and 1.0~2.5%, respectively. Proximate composition was varied in different fish species products. Mackerel and sweet fish product had a higher lipid content. Analyses of nucleotides and related compounds in six commercial products showed that IMP content of fourfinger threadfin, mackerel, house mackerel, sweet fish was 5.82 ~ 6.41 mg/100 g. The major free amino acids of six products were histidine, taurine, alanine and glycine. Mackerel product has the highest content of histidine, followed by horse mackerel. Low content of glutamic acid indicated monosodium glutamate (MSG) was not added in commercial lightly salted and dried fish products. The pH value of commercial products ranged from 5.78 to 6.8, and mackerel products were lower. Volatile basic nitrogen (VBN) in all products was less than limited level of 25 mg/100 g. The total plant count (TPC) of all commercial products were lower than limited level (3 × 106 log CFU/ g). E. Coli was not detected in all products. Mackerel lightly salted and dried product had higher levels of VBN, trimethylamine nitrogen (TMA-N), bacterial count, ash and pH value than raw mackerel. Perceptible decomposed odor occurred after mackerel stored at 7oC for 6 days, and was observed for that stored at 25oC for 32 hours. The perceptible decomposed odor was found for lightly salted and dried mackerel product stored at 7oC for 6 days and at 25oC for 32 hours. The TPC in two groupers were lower than limited level after 6 days of storage at 7oC. TPC exceeded the limited value after mackerel product stored at 25oC for 8 hours. When stored at 7oC and 25oC for 6 days and 32 hours, the amount of VBN in mackerel exceeded the limited value. VBN in mackerel product exceeded the limited value at 7oC for 6 days, but that at 25oC for 32 hours was lower than the limited value. The amount of TMA-N in both groupers increased with storage time, and the amount at 7oC was lower than that at 25oC. When mackerel and its product were stored at 7 oC for 6 days, the rapid degradation of nucleotides and related compounds to hypoxantine (Hx) occurred. K value increased when inosine (HxR) and Hx increased as mackerel and its product stored at 25oC for 8 and 16 hours. The values of TPC, TMA-N and K value were lower in the sample stored at 7oC than those at 25oC. The shelf-life of mackerel and its product was 3 days at 7oC and 8 hours at 25oC.