福建乌龙茶脂肪酸含量及差异性分析

脂肪酸是乌龙茶香气形成的关键前体。选择18个茶树品种的闽北乌龙茶（毛茶与其复焙茶）和3个茶树品种的闽南清香型乌龙茶,采用硫酸-甲醇法制备脂肪酸甲酯,运用气相色谱-质谱分析其脂肪酸的组成及含量。结果表明,福建乌龙茶中检测到11种脂肪酸,含量较高的主要是含16个和18个碳原子的脂肪酸;闽北乌龙茶的脂肪酸总量及不饱和度均低于闽南乌龙茶;十六碳酸（C16:0）、顺,顺-9,12-十八碳二烯酸（C18:2）和顺,顺-9,12,15-十八碳三烯酸（C18:3）等9种脂肪酸的含量在品种间差异显著,以雀舌的C18:3和多不饱和脂肪酸含量最高;复焙对闽北乌龙茶的脂肪酸的影响与其碳原子数和不饱和度有关,其中二十二碳酸（C22:0）和二十四碳酸（C24:0）全部降解,但含量下降最多的脂肪酸是C18:3。由此可见,福建乌龙茶的脂肪酸含量及组成差异特征与其产地有关,并受茶树品种和工艺的影响。

Analysis of Fatty Acid Compositions and Contents in Oolong Tea from Fujian Province

Fatty acids (FAs) are the key precursors for aroma formation of Oolong tea. Eighteen Minbei Oolong tea cultivars (raw and re-baked tea), and three Minnan Oolong tea cultivars with faint scent were selected as the experiment materials. The fatty acid methyl esters were prepared by the method of sulfuric acid-methanol and analyzed by gas chromatography-mass spectrometry. The results show that 11 fatty acids were detected in the Oolong teas from Fujian province, and 16C- and 18C- fatty acids were the most abundant. The total fatty acid contents and unsaturation degree from Minbei Oolong teas were lower than those of Minnan Oolong teas. The contents of nine FAs including C16:0, C18:2, C18:3, and so on, showed significant variation among different cultivars, and Queshe showed the highest C18:3 and polyunsaturated fatty acids (PUSFAs). The effect of re-baking on fatty acids in Minbei Oolong tea was related with their number of carbon atoms and unsaturation. Docosanoic acid and tetracosanoic acid degraded completely, and C18:3 content decreased more than others during re-baking process. Thus, FA contents and compositions were affected by locations, cultivars and processing technology.