气相色谱全分析海水和淡水养殖南美白对虾组织中脂肪酸组成与含量

采用超声提取-毛细管气相色谱法分析测定了海水养殖和淡水养殖的南美白对虾的肌肉和肝胰腺(中肠腺)中脂肪酸的组成与含量,以用于对虾繁殖与营养的研究。采用Folch 液超声提取对虾组织中的脂质,脂质经氢氧化钾-三氟化硼法甲酯化后上机分析。采用BPX70(60 m×0.25 mm i.d.)石英毛细管柱分离,火焰离子化检测器检测。以线性程序升温等当碳长度(ECLT)值结合标准品对照的方法对17种脂肪酸定性,用面积归一化法定量。结果表明,两种对虾的脂肪酸组成均以不饱和脂肪酸为主,而且不饱和多烯酸的含量明显高于不饱和单烯酸。两种对虾的肌肉脂肪酸中高度不饱和脂肪酸,如二十碳五烯酸(EPA)与二十二碳六烯酸(DHA)的总含量均较高,达20%以上;肝胰腺中EPA和DHA的总含量较低,为11%～17%。淡水虾中n-6族不饱和脂肪酸含量比海水虾高,海水虾中n-3族与n-6族脂肪酸含量之比值比淡水虾高。

Analysis of Fatty Acids in Tissues of Penaeus vannamei Cultured in Sea- and Fresh-Waters by Ultrasonic Extraction-Capillary Gas Chromatography

The components and contents of fatty acids in the muscle and the hepatopancreas of Penaeus vannamei cultured in the ponds of sea- and fresh-waters were determined. Lipid was extracted from tissues with "Folch" solvent under ultrasonication, and esterified with KOH-BF3 method followed by capillary gas chromatography. A fused-silica BPX70 capillary column (60 m x 0.25 mm i.d.) and flame ionization detector (FID) were employed. Fatty acids, more importantly, the positional isomers, were identified by applying equivalent chain length (ECLT) values based on even-chain saturated fatty acid methyl ester standards. Area normalization method can be used to quantify the contents of the fatty acids. The results indicated that between the two kinds of shrimps the nature of major fatty acids were the same, but there were more differences in the contents of major fatty acids. In all the tested fatty acids, the unsaturated fatty acids (UFA) were majority and the contents of polyunsaturated fatty acids were obviously higher than monounsaturated fatty acids. In the muscle lipid of the two kinds of shrimps, the total contents of eicosapentaenoic acid (EPA) and docosahexenoic acid (DHA) (highly unsaturated fatty acids) were very high, which reached to over 20%. In the hepatopancreas, the total contents of EPA and DHA were lower (ranged from 11% to 17%). Contents of n-6 cluster UFA in fresh-water shrimps were higher than that in sea-water shrimps. The value of (n-3)/(n-6) of sea-water shrimps was higher than that of fresh-water shrimps.