以一芽二叶茶鲜叶为原料,设置20、28、36℃ 3个萎凋温度梯度,取不同含水率的萎凋叶,测定茶多酚、氨基酸、黄酮、可溶性蛋白质和可溶性糖等含量,以及多酚氧化酶和过氧化物酶的酶活,并对后续加工叶的主要生化成分进行测定,研究萎凋温度对鲜叶主要生化成分和酶活性动态变化规律的影响。结果表明,随着萎凋过程鲜叶含水率的逐渐下降,茶多酚、可溶性蛋白质、可溶性糖等含量均呈现下降的趋势,36℃和28℃处理下茶多酚含量无显著差异,均高于20℃处理,可溶性蛋白质和可溶性糖含量与温度呈负相关;氨基酸和黄酮含量呈上升趋势,不同处理间36℃>28℃>20℃;CO2释放量总体呈“降-升-降”的变化趋势,以36℃处理样的释放量相对最大;多酚氧化酶活性呈缓慢下降的趋势,过氧化物酶活性呈上升趋势,且均以28℃处理酶活性最高。成品茶中28℃处理样的茶黄素、茶红素、茶多酚等含量最高,感官审评结果也表明28℃处理样的汤色、滋味等得分最高,品质最优。
By using of two leaves and a bud shoot as fresh tea leave material, setting three different withering temperature (20, 28, 36℃), sampled leaves with different moisture content, then the contents of tea polyphenols, total amino acids, flavonoids, total soluble protein, soluble sugar, PPO activity, and POD activity were determined to study the effect of withering temperature on dynamic changes of main biochemical components and enzymatic activity of tea fresh leaves, and the effects of different withering temperature on main biochemical components of rolled leaves, fermented leaves and fired tea were also analysed. The results show that with the increasing of withering time, moisture content of tea fresh leaves decrease gradually, the contents of tea polyphenols, total soluble protein and soluble sugar decrease gradually accordingly, and the contents of tea polyphenols were no difference between 28℃ and 36℃, but are obviously higher than that in 20℃; the contents of soluble protein and soluble sugar are negatively correlated with temperature; the contents of total amino acids and flavonoids increase gradually, and are positively correlated with temperature; the released amount of CO2 decreased at first, then increase and decrease finally, and the amount is the largest when the withering light temperature is 36℃; polyphenol oxidase activity shows a slow downward trend, peroxidase activity shows an upward trend, and they are the highest at 28℃. The contents of theaflavins, thearubigins, and polyphenols are also the highest at 28℃; the results of sensory evaluation also shows that the liquor color and taste of black tea at 28℃ had the highest score, with the best quality.
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