Doc:Tea
From Metabolomics.JP
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: It is fully fermented by microorganisms including ''Aspergillus spp.'' and ''Penicillium spp.'' | : It is fully fermented by microorganisms including ''Aspergillus spp.'' and ''Penicillium spp.'' | ||
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| − | | Per capita mean consumption of tea in the world is 120 mL/day <ref name=McKay>McKay DL, Blumberg JB "The role of tea in human health: An update" J Am Coll Nutr 21:1-13 | + | | Per capita mean consumption of tea in the world is 120 mL/day <ref name="McKay">McKay DL, Blumberg JB (2002) "The role of tea in human health: An update" J Am Coll Nutr 21:1-13</ref>, the second most consumed beverage in the world (next to water). <ref name="Wu">Wu CD, Wei GX (2002) "Tea as a functional food for oral health" Nutrition 18(5):443-444</ref> |
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| − | | The major phenolics in green tea include catechins (flavan 3-ols). They are (-)-epigallocatechin-3-gallate (EGCG; 59% of total catechins), (-)-epigallocatechin (EGC; 19%), (-)-epicatechin-3-gallate (ECG; 13.6%), and (-)-epicatechin (EC; 6.4%) <ref name=McKay/>. Catechins are converted to theaflavins and thearubigins in black tea <ref>USDA Database for the Flavonoid Contents of Selected Foods, Beltsville 2003</ref>. | + | | The major phenolics in green tea include catechins (flavan 3-ols). They are (-)-epigallocatechin-3-gallate (EGCG; 59% of total catechins), (-)-epigallocatechin (EGC; 19%), (-)-epicatechin-3-gallate (ECG; 13.6%), and (-)-epicatechin (EC; 6.4%) <ref name="McKay"/>. Catechins are converted to theaflavins and thearubigins in black tea <ref>USDA Database for the Flavonoid Contents of Selected Foods, Beltsville 2003</ref>. A cup of tea may contain 90 mg of EGCG <ref name="Wu"/>, but in human, EGCG is less bioavailable (i.e. absorbed) than other green tea catechins. <br/> |
| + | After drinking tea, the plasma level of catechins reach their peaks (between 1-10 µmol/L) in 2 - 4 h <ref>Yang CS, Chen L et al. (1998) "Blood and urine levels of tea catechins after ingestion of different amounts of green tea by human volunteers" Cancer Epidemiol Biomarkers Prev 7:351-354</ref>. After 24 h, plasma levels of EGCG and EGC return to baseline, but that of ECG remains elevated in methylated forms<ref>Higdon JV, Frei B (2003) "Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions" Crit Rev Food Sci Nutr 43:89-143</ref>. | ||
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Revision as of 12:41, 22 December 2009
Classification 分類
- green tea
- It is non-fermented, i.e., produced by drying an steaming the fresh leaves of Camellia sinensis var. sinensis to inactivate polyphenol oxidases.
- oolong tea
- It is produced by partial fermentation before drying.
- black tea
- It is fully fermented by oxidation.
- red (pu-erh) tea
- It is fully fermented by microorganisms including Aspergillus spp. and Penicillium spp.
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Per capita mean consumption of tea in the world is 120 mL/day [1], the second most consumed beverage in the world (next to water). [2] |
Tea Composition
| The major phenolics in green tea include catechins (flavan 3-ols). They are (-)-epigallocatechin-3-gallate (EGCG; 59% of total catechins), (-)-epigallocatechin (EGC; 19%), (-)-epicatechin-3-gallate (ECG; 13.6%), and (-)-epicatechin (EC; 6.4%) [1]. Catechins are converted to theaflavins and thearubigins in black tea [3]. A cup of tea may contain 90 mg of EGCG [2], but in human, EGCG is less bioavailable (i.e. absorbed) than other green tea catechins. After drinking tea, the plasma level of catechins reach their peaks (between 1-10 µmol/L) in 2 - 4 h [4]. After 24 h, plasma levels of EGCG and EGC return to baseline, but that of ECG remains elevated in methylated forms[5]. |
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