Effect of Low Temperature Treatment of Fresh Tea Leaves on the Quality of Yellow Tea

In order to explore the effect of low temperature treatment on the quality of yellow tea, this study took fresh leaves of ‘Jinxuan’ tea variety with one bud and one leaves as raw materials, taking natural lying at room temperature (25 ℃) as control, set 3 low temperature (10, 5, 0 ℃) and 5 treatment durations (8, 16, 24, 32, 40 h). The appearance characteristics of fresh leaves were observed and the relative conductivity, fat-soluble pigment and volatile components were determined. The sensory quality of processed yellow tea was evaluated and the main quality components were analyzed. The results showed that compared with the control group, the low temperature treatment of fresh leaves significantly increased the relative electrical conductivity, effectively reduced the chlorophyll content, and the aroma characteristics of volatiles in fresh leaves were significantly changed. Compared with the control yellow tea, low temperature treatment could effectively improve the yellow tea yellowing degree; After being treated at 10, 5 and 0 ℃ for 8 h, the contents of water extract and soluble sugar of tea increased significantly, while the contents of free amino acids in 5 ℃ and 0 ℃ treatment groups increased significantly. At the same time, the proportion of volatile substances with flower and fruit flavor in dry tea aroma increased. In conclusion, low temperature treatment of fresh leaves is helpful to improve the quality of ‘Jinxuan’ yellow tea, improve its taste mellow and aroma fragrance, and the best treatment temperature is 5~10 ℃ and duration is 16~24 h.