Abstract: Aroma enhancement is an important process to develop the flavor quality of tea. In this study, an L27 (36) orthogonal array design was employed to investigate the effect of far-infrared variable-temperature aroma enhancement technology on the flavor quality of Congou black tea as determined by sensory evaluation and analysis of flavor components. Results showed that the temperature in the third step, the temperature in the first step, the duration of the first step, the duration of the second step, the temperature in the second step, and the duration of the third step affected the overall sensory score of tea, ranked in decreasing order of importance. Under the optimized conditions: the first step lasted at 70 ℃ for 30 min, the second step lasted at 100 ℃ for 30 min, and the third step lasted at 115 ℃ for 10 min, the aroma and taste quality of raw tea were significantly improved (an increase in sensory scores by 4.66 and 5.00 points, respectively). The content of theaflavin was significantly increased from (0.70 ± 0.01)% to (0.81 ± 0.02)% (P < 0.05), whereas the contents of thearubigin and total polyphenols were significantly decreased to (6.81 ± 0.07)% and (14.79 ± 0.03)% (P < 0.05), respectively. A total of 40 aroma components in five black tea samples was detected, with alcohols being the most predominant, including 10 alcohol compounds (together accounting for 47.60% to 51.07% of the total aroma compounds). Compared to the sample without aroma enhancement, the contents of some aroma substances such as alcohols and aldehydes in Congou black tea were decreased after variable-temperature aroma enhancement, while the contents of olefines, ketones and esters were increased. Furthermore, linalool and its oxide (24.60%), geranol (13.16%), methyl salicylate (9.13%), phenylacetaldehyde (7.11%) and benzene ethanol (5.98%) were the major aroma components. Far-infrared variable-temperature aroma enhancement technology could greatly improve the flavor quality of black tea, which will provide a technical reference for improving the processing technology for Congou black tea.

Key words: Congou black tea; far-infrared variable-temperature aroma enhancement; flavor quality; aroma components