黑茶初制中主要色素物质的变化与色泽品质的形成

Variation of Main Pigments and Formation of Color Quality during the Primary Processing of Dark Green Tea

本文运用薄层色谱扫描法和分光光度法,分别测定了黑茶初制中叶绿素及其降解产物、类胡萝卜素主要组分和茶多酶氧化产物(TF、TR和TB)的变化。结果表明,在杀青、渥堆和干燥中,由于湿热作用和环境酸化,蓝绿色或黄绿色的叶绿素及其酶解产物叶绿酸酯急剧降解(尤其是叶绿素 a 和叶绿酸酯 a);β-胡萝卜素、叶黄素和新黄质虽比叶绿素相对稳定,但在各工序中亦逐渐降解。叶绿素的主要降解产物是灰黑或黄褐色的脱镁叶绿素,而灰黑或褐黑色的脱镁叶绿酸酯形成较少。渥堆期间,由于 Chl/Car 和 Chl/Phy 之比值不断下降,使得外形色泽由黄绿转变成黄褐色或黑褐色。同时,茶多酚因微生物酶促氧化和自动氧化形成了少量 TF、TR 和TB,这对黑茶橙黄明亮汤色的形成将起到积极的作用。此外,在渥堆后期还形成了其他茶类中尚未发现的未知色素 UFO1(黄褐色)和 UFO2(灰黑色)。

Variations of chlorophylls and their decomposed products,major composi-tions of carotenoid and the oxided products of tea polyphenols(TF,TR and TB)during the primary processing of dark green tea were determined with TLCscaning and spectrophotometry respectively.Results showed that chlorophyllswhich are blue green or yellow green,and chlorophyllides which are the enzy-matic decomposed or degraded products decomposed sharply(especially chloro-phyll a and chlorophyllide a),due to the action of high moisture and heatand the acidulated environment in the processes of de-enzyming,pile-fermenting and drying.β-carotene,xanthin and neoxanthin also decomposedgradually during the processes.The main decomposed products of chloro-phylls were pheophytins with grey black or yellow brown color,and pheopho-rbides with grey black or brown black color.During pile-fermenting,thecolor of appearance changed from yellow green to yellow brown or blackbrown due to the declining ratio of Chl/Car and Chl/Phy.Meanwhile,a fewof TF,TR and TB formed from oxiding polyphenols caused by microbialenzymatic oxidation and self-oxidation,which played an active role in theformation of orange-yellow and bright liquid of dark green tea.Moreover,UFO-1(yellow-brown color)and UFO-2(grey black color)which haven'tbeen found in other kinds of tea,formed at late pile-fermenting phase.