茶叶儿茶素总量比色测定的盐酸(硫酸)香草醛显色反应能力评价

测定了茶叶儿茶素及绿茶、红茶中的儿茶素与盐酸(硫酸)-香草醛的显色反应水平,通过对反应系数、准确度、精密度测定和比较,评价了儿茶素与酸性香草醛的显色反应能力。结果表明:两种酸性体系对儿茶素反应灵敏,且呈高度线性相关(R2盐酸=0.997 6±0.001 4,R2硫酸=0.997 8±0.001 8);显色反应系数上,盐酸法为34.77±10.00(绿茶)、83.83±20.13(红茶);硫酸法为39.65±8.97(绿茶)、86.68±19.87(红茶),均低于茶叶儿茶素总量经验计算公式中Roberts系数(145.68)。盐酸-香草醛显色反应体系的回收率为94.22%±3.33%(绿茶)、99.71%±1.39%(红茶),精密度的变异系数为0.08%(绿茶)、0.07%(红茶);硫酸-香草醛显色反应体系的回收率为95.78%±1.95%(绿茶)、99.95%±2.56%(红茶),精密度的变异系数为0.07%(绿茶)、0.06%(红茶),表明两种体系均能测定茶叶儿茶素总量。来源于不同茶类、等级茶的儿茶素类与酸性香草醛的显色能力差异极显著(F=37.434>F0.011,5]=6.61),说明两种反应体系均能客观表征茶叶儿茶素总量。由经验公式计算法得到的回收率(绿茶120.59%±34.86%,红茶114.09%±0.20%)和变异系数(绿茶28.91%,红茶0.17%)均不稳定,且其测定的儿茶素总量也偏高于实际值。

Evaluation of Chromogenic Reaction Ability of Hydrochloric Acid (Sulfuric Acid)-vanillin by the Colorimetry for Determining Tea Catechins Aggregates

Chromogenic reaction level of catechins from the green tea and the black tea with hydrochloric acid(sulfuric acid-vanillin)-vanillin was determined in this paper.By determining and comparing the reaction coefficient,accuracy and precision,the color reaction ability of catechins reacted with acid vanillin was evaluated.The results showed that the reaction system was sensitive to catechins with a high linear correlation(R2HA=0.997 6±0.001 4,R2SA=0.997 8±0.001 8).It was also seen that the chromogenic reaction coefficients from both systems were less than the Roberts coefficient(145.68) obtained from the empirical formula for calculating catechins aggregates.The recoveries from both system were more than 94.22 % and all the variation coefficient of precision were less than 0.08 %.This showed that both systems could determinate tea catechins aggregates.The chromogenic capability of tea catechins from different sources with acid-Vanillin was very different from each other(F=37.434>F0.01(1,5)=6.61).This results showed that two kinds of reaction systems could objectively reflect tea catechins aggregates.However,both recoveries and variation coefficient from the empirical formula were instable and the total catechins aggregates was higher than the reality.