Objective Changes on organic acids in stored Fujian Shuixian oolong tea baked at different temperatures and sour taste of the brewed tea were compared.

Method Fujian Shuixian tea was processed with high, medium or low fire-baking (baking at 130 ℃ for 1, 5, and 9 h, respectively) and stored under ambient temperature for 1, 3, 6, 9, and 15 months. At end of each storage period, samples were kept at -80°C prior to analysis for organic acids and calculation of taste activity value (TAV). The teas were also brewed to evaluate sour taste by a sensory panel for comparison.

Result Tartaric acid in the teas increased significantly after stored for a month. It, as well as citric acid, changed extremely significantly, while malic acid did significantly after 15 months. The lowest contents of malic and citric acids were found in the high fire-baked tea stored for 3 months as well as the low and medium fire-processed teas stored for 6 months. The content of succinic acid differed extremely significantly in the stored tea baked with low fire but insignificantly in those processed under medium or high fire. In contrast, fumaric acid content changed in the opposite manner. The tartaric acid TAV was greater than 10, a score indicating significant contribution to the sour taste of tea. Consequently, the samples with high tartaric acid TAV stored for same length of time, except that stored for 9 months, were brewed to taste more acidic as judged by the sensory panel.

Objective The changes in storage on organic acids in the Fujian Shuixian oolong teas processed with low, medium or high fire-baking differed significantly. The acids in combination were the source of sour taste of the brewed tea. Individually, tartaric acid played a more significant role.