Effects of different drying methods on color difference, taste and chemical components of Yunnan Congou black tea

Abstract

Drying greatly affects the quality of Yunnan Congou black tea (YCT). This study revealed the differences in color and taste of YCT between hot-air drying (HD), sun drying (SD), and pan-fired drying (PD) based on computer vision technology, electronic tongue, non-targeted metabolomics and objective quantitative techniques. The results indicated that HD had higher brightness, redness, yellowness and sweetness, SD had higher tea pigment content and bitterness, and PD presented astringency. The high retention of polyphenolic compounds in PD mainly affected its astringency, with a total catechin content 7.2 % and 20.3 % higher than HD and SD, respectively; Enzymatic oxidation in SD accelerated the degradation of polyphenols and polysaccharides, but more amino acids were retained, among which arginine and isoleucine increasing the bitterness of the tea infusion. The sucrose in HD enhanced the sweetness of the tea infusion. This study provides a theoretical basis for standardizing the quality of YCT.