Optimization of Enzymatic Oxidation Process and Quality Analysis of High-theaflavins Instant Black Tea

In order to realize the high-value utilization of summer-autumn green tea, this study used summer-autumn green tea as the raw material to develop a high-theaflavins instant black tea. Based on single-factor experiments, the enzymatic oxidation process conditions were optimized by response surface methodology. Finally the sensory evaluation, physicochemical index and aroma component of the product were analyzed. The results showed that the optimal process was as follows: Enzyme addition amount of 1/1000 (mL/mL), pH of 4.90, reacted at 50 ℃ for 44 min. Under this process condition, the product obtained, which possessed a sweet fragrance and a bright orange-red liquor color, had theaflavin content as high as 2.11%±0.04%, and physicochemical indicators all met the relevant standard requirements. A total of 70 aroma components, including 16 alcohols, 15 ketones, 6 aldehydes, 9 esters, 5 acids, 4 phenols, 5 hydrocarbons and 10 others were detected by HS-SPME combined with GC-MS. The highest relative content of alcohols was 32.34%±0.14%, and the overall aroma profile was mainly grassy and floral. The results of this study have provided a theoretical basis for the development of deep processing of tea in China.