茶树品种及摇青强度对乌龙茶脂肪酸含量的影响

Effects of tea varieties and turning over intensity on fatty acid content in Oolong tea

  • 摘要: 【目的】分析不同品种及摇青强度对茶树叶片中脂肪酸含量的影响,为乌龙茶生产中品种及摇青强度与成茶品质的关系研究提供参考依据。【方法】以黄棪、铁观音、肉桂、福建水仙、金观音和福鼎大白茶为试验材料,通过气相色谱—火焰离子化检测(GC-FID)技术检测叶片中脂肪酸含量,筛选出适宜作为摇青研究的品种;以金观音不同摇青强度叶片(鲜叶、第1次摇青叶、第5次摇青叶和第9次摇青叶)为试材,研究不同摇青强度对脂肪酸影响的差异。【结果】各茶树品种中不饱和脂肪酸含量占总脂肪酸比例达74.00%以上,各类脂肪酸含量在福建水仙中最高,铁观音中最低。6个茶树品种中共检出10种脂肪酸组分,各品种中亚麻酸、顺-亚油酸和棕榈酸含量位居前三;各品种不饱和脂肪酸含量的75.00%由亚麻酸和顺-亚油酸组成,饱和脂肪酸的含量中80.00%为棕榈酸。金观音中不饱和酸/总脂肪酸比例和亚麻酸含量最高,福建水仙中不饱和脂肪酸/总脂肪酸比例最低,顺-亚油酸含量最高。金观音中各类脂肪酸含量经摇青处理后呈先升后降的变化趋势,轻度摇青(第1次摇青叶)时不饱和脂肪酸和总脂肪酸含量最高,分别为25962.15和33249.16 μg/g;重度摇青(第9次摇青叶)时不饱和脂肪酸含量降至20731.28 μg/g,显著低于鲜叶(P<0.05)。金观音中共检出8种脂肪酸组分,3种为饱和脂肪酸,5种为不饱和脂肪酸;其中亚麻酸含量在轻度摇青时升至18113.55 μg/g,重度摇青时含量降至最低值,为13621.25 μg/g。【结论】茶树鲜叶中不饱和脂肪酸为脂肪酸的主要种类,亚麻酸、顺-亚油酸和棕榈酸为脂肪酸主要组分;摇青使叶片中脂肪酸含量下降,不饱和脂肪酸中亚麻酸含量随摇青强度增强呈先升后降的变化趋势,可能该物质作为反应底物参与乌龙茶摇青过程中脂肪酸代谢途径挥发性化合物的生成。

     

    Abstract: 【Objective】By analyzing the effect of different varieties and different turning over intensities on the content of fatty acids in tea leaves, relationships between varieties, turning over intensity and quality of Oolong tea product could be better understood.【Method】The content of fatty acids in leaves was determined by gas chromatography-flame lonization detector(GC-FID). Huangdan, Tieguanyin, Rougui, Fujianshuixian, Jinguanyin, Fuding Dabaicha were used as experimental materials to screen out the suitable varieties for the study of turning over, and the effects of different turning over intensities on fatty acids were investigated by using Jinguanyin with different turning over intensities(fresh leaves, the first turning over leaves, the fifth turning over leaves, and the ninth turning over leaves) as materials.【Result】The results showed that the content of unsaturated fatty acids was more than 74.00% in all varieties, and the content of different types of fatty acids was the highest in Fujianshuixian and was the lowest in Tieguanyin. C18:3n3, C18:2n6c, C16:1 were the top three components of 10 fatty acids detected in 6 varieties. 75.00% of the unsaturated fatty acids content in each variety was composed of C18:3n3 and C18:2n6c, and 80.00% of the saturated fatty acids content was C16:1. The unsaturated fatty acids/total fatty acids ratio and C18:3n3 content in Jinguanyin was the highest, while in Fujianshuixian, the unsaturated fatty acids/total fatty acids ratio was the lowest, and C18:2n6c content was the highest. The content of different types of fatty acids in Jinguanyin showed an upward trend first and then a downward trend during turning over process. The content of unsaturated fatty acids(25962.15 μg/g) and total fatty acids(33249.16 μg/g) both reached the highest points in slightly turning over leaves(the first truning over leaves) while the content of unsaturated fatty acids in heavily turning over leaves(the ninth turning over leaves) dropped to 20731.28 μg/g, which was significantly lower than that in fresh leaves (P<0.05). A total of 8 fatty acids components were detected in Jinguanyin, among which 3 were 3 saturated fatty acids and 5 unsaturated fatty acids. The content of C18:3n3 increased to 18113.55 μg/g when it was slightly turning over, while the content decreased to the lowest point at 13621.25 μg/g when it was heavily turning over.【Conclusion】Unsaturated fatty acids are the main fatty acids in fresh tea leaves, while C18:3n3, C18:2n6c, C16:1 are the main components of fatty acids. The content of fatty acids in leaves decrease after turning over, the content of linolenic acids in unsaturated fatty acids increases first and then decreases with the increase of turning over intensity, for they might be the reaction substrates for the formation of tea aliphatic aroma components.

     

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