冷冻处理对茶鲜叶与萎凋叶细胞破损率及红茶茶黄素含量影响研究

Effects of Freezing Treatments on the Cell Breakage Rate of Fresh and Withered Tea Leaves and the Content of Theaflavins in Black Tea

以桃源大叶和碧香早两个茶树品种的鲜叶为原料,探讨-20℃冰箱冷冻和-196℃液氮冷冻两种冷冻处理对茶鲜叶及萎凋叶细胞破损率的影响,并应用于工夫红茶的加工,进一步探讨冷冻对红茶茶黄素含量的影响。结果表明:冷冻处理有利于茶鲜叶与萎凋叶的细胞破损,其中液氮冷冻处理的细胞破损率较冰箱冷冻处理高、萎凋叶冷冻比鲜叶冷冻效果好;萎凋叶冷冻处理可以提高工夫红茶中茶黄素含量,改善茶叶品质。试验最佳工艺为:一芽二叶鲜叶经自然萎凋至含水量约为64%后液氮冷冻处理10 min→冷冻叶解冻去表面水→揉捻40 min→室温自然发酵4 h→120℃初烘至五成干→摊放30 min→75℃烘至足干。采取此工艺加工的工夫红茶茶黄素含量为0.65%±0.02%,比对照处理(0.51%±0.00%)提高27.5%,品质得到改善。

Using fresh leaves of two tea varieties of Taoyuandaye and Bixiangzao as raw materials,the effects of -20℃ refrigerator freezing and -196℃ liquid nitrogen freezing on the cell damage rate of fresh and withered tea leaves were studied,and were applied to the processing of Congou black tea to further explore the effect of freezing on theaflavins content of Congou black tea.The results showed that freezing treatment is good for cell breakage of fresh and withered tea leaves.The cell breakage rate of liquid nitrogen freezing treatment than that of refrigerator freezing treatment,and the effect of withered leaves freezing was better than that of fresh leaves.Freezing withered leaves can increase the content of theaflavins in Congou black tea and improve the tea quality.The optimal process was as follows:the fresh leaves of one bud and two leaves were withered naturally to the moisture content of about 64% and then frozen in liquid nitrogen for 10 minutes→the frozen leaves were thawed defrosted to remove the surface water→rolled for 40 minutes→naturally fermented at room temperature for 4 hours→initially dried at 120℃ to 50% dried→spread for 30 minutes→dried at 75℃ until fully dried.The content of theaflavins in Congou black tea processed by the optimal process is 0.65%±0.02%,which is 27.5% higher than that of the control treatment(0.51%±0.00%),and the tea quality has also been improved.