不同萎凋温度和时间对夏季白茶品质的影响

Effects of different withering temperatures and times on the quality of summer white tea

【目的】探究萎凋温度和时间对夏季白茶品质的影响,明确白茶品质转化关键时间点,为夏秋茶资源综合利用、白茶生产加工和品质提升提供参考。【方法】以福鼎大白茶1芽1叶为试材,采用高效液相色谱(HPLC)、Lab颜色模型、电子舌和感官审评等方法,在(65±5)%的控湿条件下研究不同萎凋温度(18、23和28℃)和不同萎凋时间(0、8、16、24、32、40和48 h)对白茶在制品色泽及成品茶感官品质、生化成分和滋味属性等方面的影响,结合系统聚类分析和主成分分析综合评价夏季白茶的最佳萎凋温度和时间。【结果】随着萎凋时间的延长,白茶在制品的含水量、色彩饱和度和色调彩度逐渐降低,颜色不断变暗、变黄,不同温度萎凋下色泽变化幅度由大到小为23℃>28℃>18℃;成茶的感官审评综合得分呈先升后降的变化趋势,18、23和28℃下的最佳萎凋时间分别为40、32和32 h,夏季白茶最适萎凋温度为23℃,有利于花香形成;茶多酚、儿茶素、表没食子儿茶素没食子酸酯和表儿茶素没食子酸酯含量整体呈下降趋势,游离氨基酸和表儿茶素含量整体呈先升高后降低的变化趋势,咖啡碱、没食子酸和没食子儿茶素含量整体呈升高趋势,茶汤的咸味和酸味呈先降低后升高的变化趋势。系统聚类分析结果表明,低温(18℃)萎凋白茶品质与其他2个萎凋温度的白茶差异明显,其品质转化最慢,转化始于萎凋16 h时,萎凋40 h时差异明显;23℃萎凋至24 h时差异明显,28℃萎凋至32 h时差异明显。主成分分析结果表明,前5个主成分累积贡献率达87.63%,第一主成分主要综合色泽、外形和苦涩味物质信息,感官审评总分、叶底得分、香气得分、涩味和咸味对第二主成分贡献率较大,第四主成分主要综合甜味物质信息。【结论】在(65±5)%的控湿条件下,综合夏季白茶在制品色泽及成品茶的感官品质、生化成分和滋味属性,明确其品质转化关键节点、最佳萎凋温度(23℃)、最佳萎凋时间(18℃40 h,23℃32 h,28℃32 h),该研究结果可用于调控夏季白茶品质风味。

【Objective】In order to explore the effect of withering temperature and time on the quality of summer white tea,clarify the key time point of white tea quality transformation,and provide reference for the comprehensive utilization of summer and autumn tea resources,white tea production and processing and quality improvement.【Method】With one bud and one leaf of Fuding Dabai tea as test material,the effects of different withering temperatures(18,23 and 28℃)and different withering times(0,8,16,24,32,40 and 48 h)on the color of white tea products and the sensory quality,biochemical components and taste attributes of finished tea were studied by high performance liquid chromatography,Lab color model,electronic tongue and sensory evaluation under the condition of humidity control(65±5)%.The optimum withering temperature and time of summer white tea were comprehensively evaluated by systematic cluster analysis and principal component analysis.【Result】The results showed that with the prolongation of withering time,the water content,color saturation and hue chroma of white tea in process gradually decreased,and the color became darker and yellower.The color change range under different temperature withering was 23℃>28℃>18℃.The sensory evaluation score of the tea increased first and then decreased.The optimum withering time at 18,23 and 28℃was 40,32 and 32 h,respectively.The optimum withering temperature of summer white tea was 23℃,which was conducive to the formation of flower aroma.The contents of tea polyphenols,catechin,epigallocatechin gallate and epicatechin gallate decreased,the contents of amino acids and epicatechin increased first and then decreased,the contents of caffeine,gallic acid and gallocatechin increased,the salty and sour tastes of tea soup decreased first and then increased.The results of cluster analysis showed that the quality of withering white tea at low temperature(18℃)was significantly different from that of other white teas at two different withering temperatures,and its quality transformation was the slowest.The transformation began at 16 h of withering,and the difference was obvious at 40 h of withering.The difference was significant at 23℃withering to 24 h and 28℃withering to 32 h.The results of principal component analysis showed that the cumulative contribution rate of the first five principal components was 87.63%.The first principal component mainly integrated the information of color,shape and bitter and astringent substances.The total score of sensory evaluation,leaf base score,aroma score,astringent and salty taste had a greater contribution to the second principal component.The fourth principal component mainly integrated the information of sweet substances.【Conclusion】Under the condition of humidity control(65±5)%,the key nodes of quality transformation,the optimum withering temperature(23℃)and the optimum withering time(18℃40 h,23℃32 h,28℃32 h)are determined by combining the color of summer white tea products and the sensory quality,biochemical components and taste properties of finished tea.The results of this study can be used to regulate the quality and flavor of summer white tea.