Caffeine in Chiang Rai tea infusions: Effects of tea variety, type, leaf form, and infusion conditions

Caffeine in Chiang Rai tea infusions was found to be dependent on infusion conditions (water temperature and infusion time), and leaf form (non-ground or ground) but independent of tea variety and type. For non-ground leaf samples, the higher the water temperature and the longer the infusion time, the higher the caffeine concentrations in tea infusions. After infusing for longer than 15 min, the dissolution rate of caffeine became slower and the concentration was essentially constant. For ground leaves, the caffeine content was not influenced by infusion time. Caffeine concentrations in tea infusions from Camellia sinensis var. sinensis (26.8 ± 0.81 and 22.3 ± 5.55 mg/100 ml for ground and non-ground samples, respectively) were not significantly different from that of Camellia sinensis var. assamica (24.4 ± 0.66 and 20.3 ± 5.07 mg/100 ml for ground and non-ground samples, respectively). The difference in caffeine concentration between green tea (28.1 ± 8.19 mg/100 ml) and oolong tea (20.3 ± 1.52 mg/100 ml) was not statistically significant.