烘焙对夏秋绿茶色泽变化的影响

Effects of Baking on Color Changes of Summer-Autumn Green Teas

【目的】研究烘焙对夏秋绿茶色泽变化的影响,为烘焙工艺在夏秋绿茶品质改良中的优化应用奠定基础。【方法】通过模拟烘焙工艺,比较分析烘焙过程茶叶感官品质、色差指标及影响色泽变化的主要理化成分等指标的动态变化。【结果】烘焙过程中夏秋绿茶颜色总体变化趋势为墨绿→黄绿→红黄→红褐色;色差指标L^(*)、a^(*)和b^(*)在相同烘焙温度下随烘焙时间的延长呈现升高的趋势;叶绿素a、b的热降解属于一级动力学反应,烘焙温度越高,叶绿素a、b的反应速率常数k越大,半衰期(t_(1/2))越短,降解速率叶绿素b>叶绿素a,烘焙过程茶多酚、儿茶素和游离氨基酸含量也呈逐渐减少的趋势。【结论】80℃烘焙茶叶色差变化较小、叶绿素的降解速率缓慢,茶多酚、儿茶素和游离氨基酸含量减少量最低,茶叶色泽品质保持最好。

【Objective】The effects of baking on the color changes of summer-autumn green teas were studied to lay a foundation for the optimal application of baking technology in quality improvement of summerautumn green teas.【Method】The baking processes of summer-autumn green tea were simulated to compare and analyze the dynamic changes of sensory quality,color difference indexes and the main physicochemical components affecting the color changes of tea leaves.【Result】The color of summer-autumn green tea changed from dark green,yellow green,red yellow to red brown during the baking process.The color difference indexes L^(*),a^(*)and b^(*)showed an increasing trend with the prolonging of baking time at the same baking temperature.During the baking process,the thermal degradation of chlorophyll(a and b)presented as a first-order kinetic reaction.With the increase of temperature,the reaction rate constant k of chlorophyll(a and b)was increased and the half-life(t_(1/2))was shortened,and the degradation rate of chlorophyll b was higher than that of chlorophyll a.The total contents of tea polyphenols,catechins and free amino acids in the baking process showed a gradually decreasing trend.【Conclusion】The color difference of tea leaves changed slightly in low temperature baking at 80℃,the degradation rate of chlorophyll was slow,the total contents of tea polyphenolics,catechins and free amino acids had lowest decrease and tea color quality could be maintained to the best level.