Determination of L-Theanine and Caffeine Contents in Tea Infusions with Different Fermentation Degrees and Brewing Conditions Using the Chromatographic Method

This study aimed to determine the caffeine and L-theanine contents in tea infusions pre- pared under varying fermentation degrees, brewing conditions (temperature and time), and serving methods (tea bag/loose-leaf). Infusions of six tea types (green, white, yellow, oolong, black, and Pu-erh) and various serving forms of green, white, and black tea were brewed at 80 ◦C and 100 ◦C for 2, 5, and 10 min. Contents were analyzed using reversed- phase high-performance liquid chromatography. Caffeine...