TEA PREPARATION AND ITS INFLUENCE ON METHYLXANTHINE CONCENTRATION

The amount of tea or coffee estimated from the number of cups consumed is frequently used as an indication of caffeine consumption in epidem iologic studies. However, this alone may be an inadequate indication o f intake since drinking practices of tea varies. In this study, methyl xanthine (caffeine, theobromine, and theophylline) contents in three b rews of four types of tea (black, oolong, green, and herbal) in both b ags and loose leaf forms were investigated to determine the actual amo unt of methylxanthines present in tea as a function of different brewi ng methods. On a dry leaf weight basis, total caffeine after three bre ws was highest in black (32.8 mg/g) and green (36.6 mg/g) tea leaves a nd lowest in Formosa oolong tea 2 (23.8 mg/g). Total theobromine was h ighest in black teas (1.64 and 1.69 mg/g) and least in oolong teas (0. 65 and 0.71 mg/g). Caffeine and theobromine were not detected in eithe r herbal tea samples, and theophylline was not detected in any tea tes ted. The overall average caffeine released in the first through third brews were 69%, 23%, and 8%, respectively. Three cups of tea brewed us ing three tea bags (Western culture) have approximately twice the amou nt of methylxanthines as the same volume prepared by three successive brews of loose tea leaves (Asian culture). These differences should be accounted for by the epidemiologic studies evaluating the effect of m ethylxanthines on health. Copyright (C) 1996 Canadian Institute of Foo d Science and Technology. Published by Elsevier Science Ltd