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==Tea Composition <small>(組成)</small>== | ==Tea Composition <small>(組成)</small>== | ||
Revision as of 16:29, 25 February 2010
Contents |
Classification of Tea 分類
Green Tea (緑茶)
It is non-fermented, i.e., produced by frying or steaming (fixation) the fresh leaves of Camellia sinensis var.sinensis to inactivate polyphenol oxidases. Steaming is common in Japan whereas pan-frying is used in China. Assan (assamica) type contains too much tannins and not suitable for green tea. Almost all green tea is consumed in Japan, Vietnam, China, and Indonesia only.
Black Tea (紅茶)
Unlike green tea, leaves are withered and rolled to crush leaf cells and release polyphenol oxidases. Black tea in India, Sri Lanka, and Kenya is manufactured by a CTC (crushing, tearing, and curling) machine whereas in China an orthodox rotorvane is used. After rolling, leaves are fermented for 0.5 - 3 hours at 25-35 °C with high humidity (>95%). Leaves are fully oxidized and turn golden with floral aroma in this process.
Oolong Tea (烏龍茶)
It is produced by partial fermentation before drying. The process is called green leaf shaking (yaoqing) and green leaf cooling (liangqing), where mildly withered tea leaves are bruised at the edges by hand. Good oolong tea leaves have reddish edges with green centers. It is mainly produced in Fujian, Guangdong (both China), and Taiwan.
Pu-erh Tea (普洱茶)
Raw pu-erh tea is produced by pressing tea leaves and fermenting for years, sometimes for decades. Ripened pu-erh tea, which is more popular, is inoculated with black Aspergillus and fermented under an optimal condition for several months. From Yunnan Pu-erh tea, Aspergillus niger, A. gloucu, and species of Penicillium, Rhizopus, Saccharomyces, and Bacterium are found. A. niger is the most predominant, followed by Saccharomyces spp. [1] Ripened pu-erh tea contains less catechins than raw pu-erh tea, but more gallic acid as the degradation products of catechins (and others). Antioxidant activity is significantly higher for raw pu-erh tea.[2]
- ↑ Jeng KC, Chen CS, Fang YP, Hou RCW, Chen YS (2007) "Effect of microbial fermentation on content of statin, GABA, and polyphenols in pu-erh tea" J. Agric. Food Chem. 55:8787-8792
- ↑ Ku KM, Kim J, Park HJ, Liu KH, Lee CH (2010) "Application of Metabolomics in the Analysis of Manufacturing Type of Pu-erh Tea and Composition Changes with Different Postfermentation Year" J. Agric. Food Chem. 58:345-352
Tea Composition (組成)
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 [2]. A cup of tea may contain 90 mg of EGCG [3], but in human, EGCG is less bioavailable (i.e. little absorbed) than other green tea catechins. However, the bioavailability is different between species and genotypes [4][5]. After drinking tea, the plasma level of catechins reach their peaks (between 1-10 µmol/L) in 2 - 4 h [6]. After 24 h, plasma levels of EGCG and EGC return to baseline, but that of ECG remains elevated in methylated forms[7]. |
緑茶中の主なフェノール化合物はカテキン(フラバン3-オール)で、(-)-エピガロカテキン-3-ガレート (EGCG; 全カテキンの59%), (-)-エピガロカテキン (EGC; 19%), (-)-エピカテキン-3-ガレート (ECG; 13.6%)そして(-)-エピカテキン (EC; 6.4%) [1]です。 紅茶ではカテキンはテアフラビンとテアルビジンに変換されます[2]。 コップ１杯のお茶にはおよそ90 mgのEGCG [3]が含まれますがEGCGは他の茶カテキンに比べ、ヒト体内にあまり吸収されません。 生物学的な利用能力は生物種や遺伝型によって変化します[4][5]。 お茶を飲んだ後、血漿中のカテキン濃度は2-4時間でピーク（1-10 µmol/L)に達します[6]。 24時間後には血漿中のEGCG, EGCは初期値に戻りますが、ECGはメチル化された形で残っています[7]。 |
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The caffeine content in different types of tea is: black tea > oolong tea > gree tea > fresh tea leaf [9]. More than 200 mg/day caffeine is not advisable and may produce nervousness, sleep disorders, vomits, headaches, epigastric pain, and tachycardia [10]. |
異なる茶に含まれるカフェインの量は 紅茶＞ウーロン茶＞緑茶＞新鮮な茶葉[9]となります。 200 mg/日以上のカフェイン摂取は、イライラ、不眠、吐き気、頭痛、胃痛や頻脈を引き起こすので薦められません[10]。 |
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- References
- ↑ 1.0 1.1 McKay DL, Blumberg JB (2002) "The role of tea in human health: An update" J Am Coll Nutr 21:1-13
- ↑ 2.0 2.1 USDA Database for the Flavonoid Contents of Selected Foods, Beltsville 2003
- ↑ 3.0 3.1 Wu CD, Wei GX (2002) "Tea as a functional food for oral health" Nutrition 18(5):443-444
- ↑ 4.0 4.1 Kim S, Lee MJ, Hong J (2000) "Plasma and tissue levels of tea catechins in rats and mice during chronic consumption of green tea polyphenols" Nutr Cancer 37:41-48
- ↑ 5.0 5.1 Loktionov A, Bingham S et al. (1998) "Apolipoprotein E genotype modulates the effect of black tea drinking on blood lipids and blood coagulation factors: A pilot study" Br J Nutr 79:133-139
- ↑ 6.0 6.1 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
- ↑ 7.0 7.1 Higdon JV, Frei B (2003) "Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions" Crit Rev Food Sci Nutr 43:89-143
- ↑ Belitz DH, Grosch W (1997) "Quimica de los Alimentos" Zaragoza Acribia
- ↑ 9.0 9.1 Lin Lin YS, Tsai YJ et al. (2003) "Factors affecting the levels of tea polyphenols and caffeine in te a leaves" J Agric Food Chem 51:1864-1873
- ↑ 10.0 10.1 Varnam AH, Sutherland JP (1994) "Beverages: Technology, Chemistry and Microbiology" Chapman & Hall (London)
- ↑ Cabrera C, Artacho R, Gimenez R (2006) "Beneficial Effects of Green Tea-A Review" J Am Coll Nutr 25(2):79-99
Tea and Human Health (健康情報)
Cancer 癌
As below, none of the large-scale epidemiological studies showed a significant association of tea intake with a lower risk of cancer[1]. However, many case-control studies and cross-sectional studies (up to several hundreds people) show a decrease of the risk of cancer.
- Breast cancer 乳がん
- Two prospective studies with 35,004 women [2] → no association
- Gastrointestinal cancer 胃腸がん
- Bladder cancer 膀胱がん
- Prospective cohort 14873 men and 23667 women [3] → no association
- Cancer incidence がん
- Prospective study 38540 people [3] → no association
- References
- ↑ Borrelli F, Capasso R et al. (2004) "Systematic review: green tea and gastrointestinal cancer risk" Aliment Pharmacol Ther 19:497-510
- ↑ Suzuki Y, Tsubono Y et al. (2004) "Gren tea and the risk of breast cancer: pooled analysis of two prospective studies in Japan" Br J Cancer 90:1361-1363
- ↑ 3.0 3.1 3.2 Nagano J, Kono S et al. (2001) "A prospective study of green tea consumption and cancer incidence, Hiroshima and Nagasaki (Japan)" Cancer Causes Control 12:501-508
- ↑ Tsubono Y, Nishino Y et al. (2001) "Green tea and the risk of gastric cancer in Japan" New Engl J Med 344:632-636
- ↑ Hoshiyama Y, Kawaguchi T et al. (2002) "A prospective study of stomach cancer death in relation to green tea consumption in Japan" Br J Cancer 87:309-313
- ↑ Fujino Y, tamakoshi A et al. (2002) "Prospective study of education background and stomach cancer in Japan" Prev Med 35:121-127
Cardiovascular Disease (CVD) 循環器疾患
It is often believed that (oolong) tea possesses hypotensive effects. After Hertog MG et al.[1], flavonoid intakes have been reported to inversely associated with CVDs. In 2008, Hooper et al. performed a comprehensive review of reliable 133 flavonoid trials[2], and concluded that
- flavanol-rich cocoa reduces blood pressure by 6 (systolic) and 3 (diastolic) mm Hg,
- soy protein, which is rich in isoflavones, reduces LDL cholesterol by 0.2 mmol/L,
- black tea acutely (not chronic) raises blood pressure by 6 (systolic) and 3 (diastolic) mm Hg, and
- chocolate acutely (not chronic) increases flow-mediated dilation (FMD) by 4%.
- References
- ↑ Hertog MG, Feskens EJ (1993) "Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study" Lancet 342(8878):1007-1011
- ↑ Hooper L, Kroon PA, Rimm EB, et al. "Flavonoids, flavonoid-rich foods, and cardiovascular risk: a meta-analysis of randomized controlled trials" Am J Clin Nutr 88:38–50
- ↑ Geleijnse JM, Hollman PCH (2008) "Flavonoids and cardiovascular health: which compounds, what mechanisms?" Am J Clin Nutr 88:12-13
- ↑ Rimm EB, Katan MB (1996) "Relation between intake of flavonoids and risk for coronary heart disease in male health professionals" Ann Intern Med 125(5):384-389 and Huxley RR, Neil HA (2003) "The relation between dietary flavonol intake and coronary heart disease mortality: a meta-analysis of prospective cohort studies" Eur J Clin Nutr 57:904–908
Obesity 肥満
Recently, resveratrol is found to improve obesity.[1]. Some studies suggest relationship between green tea consumption and reduction in body fat[2][3], but clear evidence on body weight control is missing. Since body weight may change for various reasons, it is hard to conduct an epidemiologic study.
- References
- ↑ Baur JA et al. Sinclair DA (2006) "Resveratrol improves health and survival of mice on a high-calorie diet" Nature 444:337-342
- ↑ Wu CH, Lu FH et al. (2003) "Relationship among habitual tea consumption, percent body fat, and body fat distribution" Obes Res 11:1088-1095
- ↑ Tian WX, Li LC et al. (2004) "Weight reduction by Chinese medicinal herbs may be related to inhibition of fatty acid synthase" Life Sci 74:2389-2399
