Changes in theanine and caffeine contents of black tea with different rolling methods and processing stages

Abstract

Theanine is a specific amino acid in tea, which has positive effects on health. Theanine contents of different grade Turkish teas, variations in the theanine content during tea processing, and the effects of different rolling processes on theanine content were determined. Theanine content of Turkish tea varying between 0.32 and 0.43 % has been reported for the first time by this study. Theanine content decreased in all processing steps from 10.0–3.42 to 7.73–3.97 mg g−1 dw in Orthodox and Cay-Kur methods, respectively. In both methods, the highest theanine loss (almost 50 %) was observed in the withering step, which was followed by drying step. Caffeine content of Turkish tea was determined varying between 1.8 and 2.2 %. While the caffeine content increased in the withering step, it decreased in other steps. The correlation between theanine and caffeine contents was evaluated. A high correlation (R 2 = 0.87) between the caffeine and theanine contents was found in teas classified by Cay-Kur method, and caffeine/theanine ratio was found to be around 5.3 in general.