Shirai Nobuya
National Agriculture and Food Research Organization, Institute of Fruit Tree and Tea Science.
J Oleo Sci. 2019;68(12):1271-1277. doi: 10.5650/jos.ess19208.
Herein, gas chromatography is used to determine and quantify organic acids in Japanese green tea leaves, and the established method is employed to profile the acid components of Matcha, Gyokuro, Sencha green teas, and green tea varieties and thus acquire data needed to ensure the high quality and safety of green tea. The tea leaves were esterified with 10 vol% sulfuric acid in 1-butanol at 100℃ for 2 h. Oxalic acid contents were high in Asatsuyu and Okuyutaka samples and were low in Sofu, increasing in the order of Sencha < Gyokuro < Matcha, while citric acid content increased in the order of Sencha < Matcha < Gyokuro. Moreover, the oxalic acid content of Gyokuro only slightly increased with increasing tea grade. The relative contents of the different fatty acids did not strongly vary between the different green tea varieties. However, the n-3 to n-6 ratio was found to be low in Sofu. The progressing maturity increased the n-3 to n-6 ratio of Yabukita. The n-3 to n-6 ratio was low in high-grade Matcha, Gyokuro, Sencha green teas, and was related to the green tea quality. The developed method was concluded to be suitable for the evaluation of green tea quality.
在此，采用气相色谱法测定和定量分析日本绿茶中的有机酸，并运用所建立的方法对抹茶、玉露、煎茶等绿茶品种的酸成分进行剖析，从而获取确保绿茶高品质和安全性所需的数据。茶叶在100℃下用10体积%的硫酸在正丁醇中酯化2小时。浅玉露和奥汤高样品中的草酸含量较高，而初老中的草酸含量较低，其含量按煎茶<玉露<抹茶的顺序增加，而柠檬酸含量按煎茶<抹茶<玉露的顺序增加。此外，玉露的草酸含量仅随茶叶等级的增加而略有增加。不同脂肪酸的相对含量在不同绿茶品种之间变化不大。然而，发现初老中的n-3与n-6比例较低。矢吹的n-3与n-6比例随着成熟度的增加而增加。高档抹茶、玉露、煎茶中的n-3与n-6比例较低，且与绿茶品质有关。得出所建立的方法适用于绿茶品质评价的结论。
