鲜叶萎凋前期低温处理对金萱白茶品质的影响

为探究萎凋前期低温处理对金萱白茶品质的影响，采用金萱茶树品种一芽二叶鲜叶为原料，在萎凋前期进行低温不同时长处理，再经室内自然萎凋和干燥制成白茶，并通过感官审评、气相色谱-质谱法（gas chromatography-mass spectrometry，GC-MS）和电子舌对白茶香气和滋味进行了分析。结果表明，萎凋前期低温（5 ℃）处理加工的白茶与对照的品质有明显差异，低温处理提升了白茶香气的持久度及甜香、花香强度，增加了呈香挥发性物质的种类和含量，5 ℃低温处理40 h的白茶较对照样增加了21种呈香挥发性物质，5 ℃低温处理30 h的白茶香气呈香挥发性物质总量增加幅度最大，约为对照的5倍。同时，低温处理可以增加白茶滋味的醇厚度，降低苦涩味，5 ℃低温处理50 h的白茶滋味甜度最高，较对照增加了7.28%。综上，鲜叶萎凋前期低温处理有助于提升金萱白茶的品质，综合品质以5 ℃低温处理30 h的白茶为最佳。

Effect of Low Temperature Treatment on the Quality of Jinxuan White Tea in the Early Stage of Fresh Leaves Withering

In order to explore the effect of low temperature treatment on the quality of Jinxuan white tea in the early stage of withering, the fresh leaves of Jinxuan tea variety with one bud and two leaves were used as raw materials. In the early stage of withering, the smart refrigerator was used for low temperature and different length treatment. The white tea was made according to the indoor natural withering and drying process. The aroma and taste of white tea were analyzed by sensory evaluation, gas chromatography-mass spectrometry and electronic tongue. The results showed that the quality of white tea processed at low temperature (5 ℃) treatment in the early withering stage was significantly different from that of the control. Low temperature treatment improved the persistence of white tea aroma and the intensity of sweet aroma and flower aroma, and increased the types and contents of fragrant volatile substances. The white tea treated at 5 ℃ for 40 h increased 21 kinds of fragrant volatile substances compared with the control. The total amount of fragrant volatile substances of white tea treated at 5 ℃ for 30 h increased the most, about 5 times that of the control. At the same time, low temperature treatment could increase the alcohol thickness of white tea taste and reduce the bitter taste. The taste sweetness of white tea treated at 5 ℃ for 50 h was the highest, which increased by 7.28% compared with the control. Therefore, low temperature treatment in the early stage of fresh leaves withering was helpful to improve the quality of Jinxuan white tea. The best comprehensive quality was the white tea treated at 5 ℃ for 30 h.