绿茶茶汤中黄酮醇及其苷类的测定方法以及对茶汤色度的影响

黄酮醇及其苷类物质是构成绿茶汤色的重要组分。绿茶中含有20多种黄酮醇及其苷类物质,其中以槲皮素、杨梅素、山柰素的3种苷类物质为主。文中采用高效液相色谱法研究了绿茶茶汤酸水解前后槲皮素、杨梅素、山柰素的含量变化,建立了黄酮醇及其苷类含量的检测方法。利用正交实验方法得到茶汤水解的优化条件为:5 mL的茶汤中加15 mL纯甲醇、5 mL 6 mol/L HCl,在75℃下水解时间2h,芦丁的平均水解率为82.74%。对不同贮藏期间茶汤色度与黄酮醇及其苷类的相关性进行了研究,结果表明:茶汤贮藏过程中随着茶汤的红绿度(a)和黄蓝度(b)不断升高,杨梅素苷含量逐步下降,杨梅素苷与茶汤的红绿度、黄蓝度的相关系数分别为:-0.982 1、-0.882 6,但与茶汤明亮度(L)的相关性不显著。槲皮素和山柰素及其苷类与茶汤色泽变化关系不密切。

Study on the Determination of Flavonols and Its Glycosides and Their Effects on the Color of Green Tea Infusion

Flavonol and its glycosides are the main components contribute to the color of green tea infusion.Green tea contains over 20 kinds of flavonol and its glycosides,among of which quercetin,myricetin,kaempferol and their glycosides are major components.The determination of flavonol and its glycosides in green tea infusion were studied by HPLC analysis.It was based on the changes of quercetin,myricetin,kaempferol before and after hydrolysis of tea infusion.According to orthogonal experiment,the optimal hydrolytic conditions for green tea infusion were 2 hours at 75℃ with 100% methyl alcohol and 6 moloL-1 hydrochloric acid.The correlations between flavonol and its glycosides and color of tea infusion during storage were investigated.The results showed that the redness(a)and yellowness(b) increased as the decrease of myricetin glycosides contents.The coraltion coefficients of myricetin glycosides to the redness(a)and yellowness(b) of green tea infusion was-0.982 1** and-0.88 26*,respectively.However,the correlations between the color of tea infusion and quercetin,myricetin,kaempferol and their glycosides were not remarkable.