Preparation of partially decaffeinated instant green tea.
The caffeine level of instant tea extracted from decaffeinated leaf tea with 4.0 mg g-1 caffeine is commonly above 10.0 mg g-1, the maximum limit of caffeine for decaffeinated instant tea. Further removal of caffeine by active carbon (AC) from the green tea extract was investigated. It showed that the removal of caffeine from the tea extract solutions depended on the treatment time and tea extract concentration while the ethanol concentration and pH had little effect on the removal of caffeine. According to the removal of caffeine and the ratio of total catechins to caffeine in the tested samples, the optimum decaffeination conditions were determined to be as follows: tea extract concentration 15-30 g L-1 for common tea extract but higher for partially decaffeinated tea leaf extract; ratio of tea solution to AC, 100 mL:4 g; treatment time, 4 h; and natural tea extract pH. Instant tea powder extracted from partially decaffeinated leaf tea with a caffeine level of 4.03 mg g-1 and further decaffeinated by AC had a caffeine level of 7.81 mg g-1, which was 31% lower than that without AC treatment.
Ye
Jian-Hui
JH
Zhejiang University Tea Research Institute, 268 Kaixuan Road, Hangzhou 310029, People's Republic of China.
Liang
Yue-Rong
YR
Jin
Jing
J
Liang
Hue-Ling
HL
Du
Ying-Ying
YY
Lu
Jian-Liang
JL
Ye
Qian
Q
Lin
Chen
C
D002110:Caffeine / Q000032:analysis*; D028241:Camellia sinensis / Q000737:chemistry; D002244:Carbon; D002392:Catechin / Q000032:analysis; D005419:Flavonoids / Q000032:analysis; D005511:Food Handling / Q000379:methods; D006863:Hydrogen-Ion Concentration; D010936:Plant Extracts / Q000737:chemistry; D018515:Plant Leaves / Q000737:chemistry; D013662:Tea / Q000737:chemistry*
D005419:Flavonoids; D010936:Plant Extracts; D013662:Tea; D002110:Caffeine; D002244:Carbon; D002392:Catechin