摘要：In the present work, Turkish black teas were analyzed to investigate some different effects on the level of caffeine.
Firstly, by the effect of shooting period and tea grades (seven grades) for teas manufactured with Orthodox method.
And secondly, by the effect of the processing method for two tea types, Orthodox and Cay-kur (orthodox+ rotorvane+
orthodox) obtained from Turkish Tea Board (Cay-Kur, Turkey). After an analytical determination of caffeine levels by
HPLC (High-Performance Liquid Chromatography), the obtained results were as follows: for shooting periods, the
levels of caffeine had a range between 1.74 and 2.11% of dry weight. Also, levels revealed a significant difference
(p<0.05) and a decrease in content from spring to autumn (May, June, to September). However, there was no
significant difference (p>0.05) between the seven grades of Turkish black tea. Even the different manufacturing
methods had no significant effect on caffeine levels. The amount of caffeine was similar, 2.21% in Orthodox method and
2.16 % in Cay-kur tea. Finally, it is found that shooting period had a significant effect on caffeine content, the highest
caffeine levels were obtained during the first shooting period (May) of tea plucking period, while the lowest levels were
in the third shooting period (September). Hence, the shooting period factor confirms its effect on the caffeine levels.
关键词：Black tea; caffeine; grades; manufacturing method; shooting period
