45I-9 |
Flavonoid composition of tea: Comparison of black and green teas |
S. Bhagwat1, G. R. Beecher2, D. B. HAYTOWITZ1, J. M. Holden1, J. T. Dwyer3, J. J. Peterson3, S. Gebhardt1, A. L. Eldridge4, S. Agarwal5, and D. A. Balentine5. (1) Nutrient Data Lab., USDA-ARS-Beltsville Human Nutrition Research Center, 10300 Baltimore Ave., Bldg. 005, Rm. 202, Beltsville, MD 20705-2325, (2) Food Composition Lab., USDA-ARS-Beltsville Human Nutrition Research Center, 10300 Baltimore Ave., Bldg. 161, Beltsville, MD 20705-2350, (3) School of Nutrition Science & Policy, Tufts Univ. School of Medicine, Francis Stern Nutrition Ctr., 750 Washington St., Boston, MA 02111-1526, (4) Bell Institute of Health & Nutrition, General Mills, Inc., 9000 Plymouth Ave. N., Minneapolis, MN 55427-3899, (5) Unilever Bestfoods North America, 800 Sylvan Ave., Englewood Cliffs, NJ 07632-3201 Tea, the most widely consumed beverage in the world, is produced from the leaves of Camelia sinensis. The type of tea produced depends on the length of fermentation of the leaves–green tea is not fermented, black tea is nearly completely fermented, while Oolong tea is partially fermented. The prominent flavonoids in the tea are the flavanols catechin, epicatechin, epicatechin gallate, epigallocatechin, and epigallocatechin gallate and their fermentation products, derived tannins--theaflavins and thearubigins. Some epidemiological studies, clinical trials and animal studies have shown association between tea drinking and reduced risk of chronic diseases, particularly cardiovascular diseases and some cancers. To develop a database on the flavonoid content of teas to aid researchers in assessing the dietary intake of these compounds. We have collected and evaluated analytical data on all teas through extensive literature searches and new analytical data provided by Unilever Bestfoods North America. Data analysis revealed following: Green and black teas contain comparable amounts of total flavonoids, but green tea contains mostly catechins, about 4.5 times that of black tea. As tea leaves are fermented, theaflavins and thearubigins increase, while catechins decrease. Black tea has 95 times more theaflavins and 45 times more thearubigins compared to green tea. Decaffeination reduces total catechins in both black and green tea by about 14 times and 5 times respectively. Decaffeinated green tea contains comparable amounts of total catechins (3,942mg/100g) as in regular black tea (3,320 mg/100g). The flavonols quercetin, kaempferol and myricetin are not affected either by fermentation or by decaffeination. All ready to drink teas, black, green or made from powder have approximately a fifth to a tenth of the flavonoids compared to similar teas brewed from leaves or tea bags. The type of tea and the preparation techniques must be considered in assessing tea flavonoid contents.
Session 45I, Nutrition: General
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