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Stability of Green Tea Catechins in Commercial Tea Leaves during Storage for 6 Months
Author(s) -
Friedman Mendel,
Levin C.E.,
Lee S.U.,
Kozukue N.
Publication year - 2009
Publication title -
journal of food science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.772
H-Index - 150
eISSN - 1750-3841
pISSN - 0022-1147
DOI - 10.1111/j.1750-3841.2008.01033.x
Subject(s) - catechin , chemistry , epicatechin gallate , food science , green tea , epigallocatechin gallate , gallate , polyphenol , high performance liquid chromatography , statistical analysis , chromatography , biochemistry , mathematics , nuclear chemistry , antioxidant , statistics
To help meet the needs of consumers, producers of dietary tea products, and researchers for information on health‐promoting tea ingredients, we determined by HPLC 7 catechins [(−)‐epigallocatechin (EGC), (−)‐catechin (C), (+)‐epicatechin (EC), (−)‐epigallocatechin 3‐gallate (EGCG), (−)‐gallocatechin 3‐gallate (GCG), (−)‐epicatechin 3‐gallate (ECG), and (−)‐catechin 3‐gallate (CG)] in samples of 8 commercial green tea leaves of unknown history sold as tea bags in the United States, Korea, and Japan. The samples were stored at 20 °C and sampled at 1 wk and 1, 2, 4, and 6 mo. The following ranges in the initial values (0 controls) were observed (in mg/g tea leaves): EGC and C, 0 to trace amounts; EC, 1.9 to 21.1; EGCG, 13.3 to 113.0; GCG, 0.2 to 1.6; ECG, 5.7 to 50.5; CG 0.5 to 3.7; total catechins 36.5 to 169.7. Statistical analysis of the results and plots of changes in individual and total catechin levels as a function of storage time indicate a progressive decrease in the content in the total levels, most of which is due to losses in the most abundant catechins, EGCG and ECG. Possible mechanisms of degradations of catechins during storage and the possible significance of the results to consumers of tea are discussed.