Abstract:Baojing Huangjincha 1 was used as the raw material to produce congou black tea, and the effects of fermentation at variable temperatures (40 ℃ in the first stage and 30 ℃ in the second stage) on the quality of congou black tea were investigated. The results showed that the color of congou black tea fermented at variable temperatures was dark brown and moist, the taste was sweet, mellow, and fresh, the sweetness was long-lasting, the soup was red and bright, and the leaf bottom was red and even. Compared to fermentation at a constant temperature, the color of the tea soup changed significantly from bright red to dull red, the taste developed from sweet alcohol to pure and sweet, and the leaf bottom gradually became dark and tarnished (turned from bright red to reddish brown); these effects became more prominent as the fermentation time in the first stage (40 ℃) was extended. Compared to variable-temperature fermentation, the content of amino acids and tea polyphenols showed the greatest decrease after 3 h of constant-temperature fermentation at 40 ℃, and changes in the tea polyphenol, amino acid, and soluble sugar contents were generally the same as that observed after fermentation for 4 h at 30 ℃ and a constant temperature. The final content of theaflavins (0.39%) after variable-temperature fermentation was higher than that obtained after fermentation at constant temperatures (30 ℃ and 40 ℃). Based on the results of sensory evaluation and content of quality components in each treatment, variable-temperature fermentation (40 ℃, 1 h+30 ℃, 2 h) is optimal for processing congou black tea with a sweet, mellow, and fresh taste.
