Comparison of catechins and aromas among different green teas using HPLC/SPME-GC

Green tea polyphenols (GTP) from Camellia sinensis (L.) O. Kuntze are the major water soluble components in tea liquor. The GTP extraction yield was determined using different extraction times from 10 to 60 min at 70 degrees C, and also at different temperatures from 50 degrees C to 100 degrees C, keeping the extraction time constant. The composition of the GTP (catechins) from samples of different origins was determined by RP-HPLC, measuring the absorbance at 280 nm. The calibration curves of the catechins were linear between 5 ng and 2 mu g, and their C.V. values for the quantitation were less than 4.0% for four replicates using four different sets of each type. The total epicatechin derivatives (EPD) and epigallocatechin-3-gallate (EGCG) from Azorean green tea, accounted for 74.5 and 47.9% (w/w) of the total GTP, respectively, and were compared with that from tea samples of different origins. The EGCG:caffeine ratio in Azorean green tea was fourfold higher as compared with others, which suggested a good source of a chemopreventive agent. The aroma composition of different green tea samples was compared using the SPME/GC headspace methodology. (C) 1999 Canadian Institute of Food Science and Technology. Published by Elsevier Science Ltd. All rights reserved.