Kim Mingi, Park Seung-Kook
Department of Food Science and Biotechnology, Kyung Hee University, Yongin-si, Gyeonggi-do 17104 Republic of Korea.
Food Sci Biotechnol. 2022 Mar 15;31(5):539-547. doi: 10.1007/s10068-022-01063-6. eCollection 2022 May.
Green tea contains polyphenols, mainly four catechins, including (-)-epigallocatechin gallate, (-)-epicatechin gallate, (-)-epigallocatechin, and (-)-epicatechin. Enzyme tannase is known to hydrolyze gallated catechins into non-gallated catechins and gallic acid (GA). In this study, dried green tea leaves were treated with tannase to determine changes of volatile and non-volatile compounds by the hydrolysis. The results indicated that (-)-epigallocatechin, (-)-epicatechin, and GA increased, while (-)-epigallocatechin gallate and (-)-epicatechin gallate decreased after the treatment. The GA level increased in the treated samples, which increased titratable acidity significantly, while the pH became lower. Furthermore, the antioxidant activity of the tannase-treated tea leaves increased. The level of glycosidically bound aromas decreased with the concomitant increase of corresponding volatile compounds, while some alcohols derived from fatty acids decreased significantly after the treatment. These results suggest that tannase-treatment influences both volatile and non-volatile compounds in dried green tea leaves.
绿茶含有多酚类物质，主要是四种儿茶素，包括（-）-表没食子儿茶素没食子酸酯、（-）-表儿茶素没食子酸酯、（-）-表没食子儿茶素和（-）-表儿茶素。已知单宁酶能将没食子酰化儿茶素水解为非没食子酰化儿茶素和没食子酸（GA）。在本研究中，用单宁酶处理干燥的绿茶茶叶，以确定水解过程中挥发性和非挥发性化合物的变化。结果表明，处理后（-）-表没食子儿茶素、（-）-表儿茶素和GA增加，而（-）-表没食子儿茶素没食子酸酯和（-）-表儿茶素没食子酸酯减少。处理后的样品中GA水平增加，显著提高了可滴定酸度，同时pH值降低。此外，单宁酶处理的茶叶的抗氧化活性增加。糖苷结合香气的水平随着相应挥发性化合物的增加而降低，而一些源自脂肪酸的醇类在处理后显著减少。这些结果表明，单宁酶处理会影响干燥绿茶茶叶中的挥发性和非挥发性化合物。
