摘要
探索针形茶变温变频理条工艺与机制,为实现针形茶自动化理条提供依据。比较不同的变温变频理条方式对茶叶品质的影响,分析针形茶变温变频理条的内在机制。结果表明,采用"高-高-中"方式理条的茶样感官品质得分最高(93分),香气尚鲜栗香、滋味尚鲜醇、叶底绿明亮,干茶、茶汤、叶底的-a*值分别高达0.47、5.07、3.33;茶多酚、氨基酸、可溶性糖质量分数和总叶绿素含量较高,分别为28.65%、2.64%、3.78%和3.68 mg/g。在固定温度与频率情况下,理条前期,水分质量分数无显著变化,叶温、热容量、焓迅速升高,3 min时分别高达64.4℃、4.88 k J/(kg/℃)、173 k J/kg;中期,水分质量分数逐步减少,叶温逐渐上升,热容量保持稳定,焓迅速降低;后期,水分质量分数下降较快,叶温升高缓慢,热容量及焓降低,理条结束时焓最低,为147 k J/kg;熵变不断减少且大于零,说明理条过程不可逆,平均失水率为2.78%/min。理条过程中所吸收的热量,不同阶段其作用表现不同:理条前期以升温为主;中期以失水、升温为主;后期以失水为主,升温为辅。采取前期高温高频、后期适当降温降频的理条方式有利于形成针形茶色绿、鲜醇的品质。
This study aimed to explore the shaping of needle-shaped green tea at variable temperature and variable frequencies and to reveal the underlying mechanism for the purpose of providing the basis for automated shaping of needleshaped green tea. The effects of different variable-temperature variable-frequency shaping regimes on the quality of tea were compared, and the intrinsic mechanism underlying the shaping process was elucidated. The results showed that the tea samples produced by ＂high-high-middle＂ shaping scored highest（93 points） in sensory evaluation, having a fresh chestnutlike aroma, a fresh and mellow taste and a green and bright color. The-a＊ values of the tea, tea infusion and tea leaves were 0.47, 5.07 and 3.33, respectively. The contents of tea polyphenols, amino acids, soluble sugar and chlorophyll in the tea were 28.65%, 2.64%, 3.78% and 3.68 mg/g. The moisture content showed no significant change during the early period of shaping at constant temperature and frequency, while the leaf temperature, caloricity and enthalpy increased quickly, reaching 64.4 ℃, 4.88 k J/（kg/℃） and 173 k J/kg at 3 min, respectively. During the middle period of shaping, the moisture content continuously decreased and the leaf temperature rose, accompanied by unchanged caloricity and a rapid decrease of enthalpy. During the late period of shaping, the moisture content fell rapidly, and the leaf temperature rose slowly, along with a simultaneous decrease in caloricity and enthalpy. At the end of shaping, the lowest enthalpy of 147 k J/kg was observed. The entropy change reduced gradually but was always greater than zero, suggesting that the shaping process was irreversible. The average rate of water loss was 2.78%/min. The heat absorbed at different stages of the shaping process played different roles. Temperature rise mainly occurred at the early stage, both water loss and temperature rise mainly occurred at the middle stage, and the late stage was dominated by water loss, followed by temperature rise. To sum up, high temperature and high frequency for the early stage followed by proper reduction for the late stage helped the formation of green color and fresh and mellow taste in needle-shaped tea
作者
罗红玉
吴全
钟应富
袁林颖
张莹
杨娟
唐敏
王明乐
黎星辉
LUO Hongyu;WU Quan;ZHONG Yingfu;YUAN Linying;ZHANG Ying;YANG Juan;TANG Min;WANG Mingle;LI Xinghui(Tea Research Institute,Chongqing Academy of Agricultural Sciences,Chongqing 402160,China;Chongqing Engineering Research Center for Tea,Chongqing 402160,China;National Tea Industry Technical System Chongqing Comprehensive Experimental Station,Chongqing 402160,China;College of Horticulture,Nanjing Agricultural University,Nanjing 210095,China)
出处
《食品科学》
EI
CAS
CSCD
北大核心
2018年第13期119-124,共6页
Food Science
基金
重庆市科委应用开发计划项目(cstc2013yykf B80020)
重庆市科委基本科研业务费计划项目(2013cstc-jbky-00530)
现代农业产业技术体系建设专项(CARS-23)
国家自然科学基金面上项目(31570689)
重庆市农业科学院基础科研项目(NKY-2015AC012)
关键词
针形茶
变温变频
理条工艺
品质
机制
needle-shaped green tea
variable temperatures and variable frequencies
shaping
quality
mechanism
