Doc:Tea

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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]

  1. ↑ 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
  2. ↑ 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

Consumption (消費)

 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). Black tea is principally consumed in Western countries, green tea is popular in Asia, and oolong tea in China and Taiwan[2]. 世界における茶の一人当たり消費量は 120 ml/日 [1]で、世界で飲まれる飲料ナンバー２です。紅茶は主に西洋で飲まれ、緑茶はアジア、ウーロン茶は中国と台湾で飲まれます[2]。
World tea consumption (1000 tons)
location 1996-2000 2001 2002 2003 2004 2005
world 2833 2985 3093 3199 3227 3362
India 635 671 693 714 735 757
China 482 496 538 555 604 675
Russia 146 156 166 167 169 180
Japan 138 149 135 138 156 150
Pakistan 109 107 99 118 120 134
United Kingdom 142 137 134 119 129 128
United States 91 97 94 94 100 100
　Source: FAO 2006. Current market situation and medium term outlook. [3]
Green tea consumption (1000 tons)
location 2000 2001 2002 2003 2004 2005
world 681 782 784 756 832 884
China (mainland) 343 350 376 388 418 485
Japan 109 107 94 101 116 114
Vietnam 16 16 18 17 17 19
Indonesia 30 33 34 37 37 31
Source: Annual bulletin of statistics 2006 (International Tea Committee)

[3]

World tea production (1000 tons)
location 2001 2002 2003 2004 2005
world 3046 3174 3249 3388 3504
China 722 766 791 856 940
India 856 883 907 893 928
Kenya 295 287 294 325 329
Sri Lanka 296 311 303 308 317
Turkey 143 150 155 206 206
Indonesia 173 173 168 170 166
Vietnam 82 93 95 97 104
Source: FAO 2006. Current market situation and medium term outlook [3]
  1. Tea consumption ranking in the world (in Japanese)
  2. Tea comsumption in Japan (in Japanese)
References
  1. ↑ 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. ↑ 2.0 2.1 Wu CD, Wei GX (2002) "Tea as a functional food for oral health" Nutrition 18(5):443-444
  3. ↑ 3.0 3.1 3.2 Ho CT, Lin JK, Shahidi F (Eds.) (2009) Tea and Tea Products Nutraceutical Science and Technology 8 CRC Press

Tea Composition (組成)

Catechins

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].
カテキン

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]。

Major Composition (%)[8]
Compound Green tea Black tea Black tea
Infusion (3min)
Proteins 15 15 trace
Amino acids 4 4 3.5
Fiber 26 26 0
Others, carbohydrates 7 7 4
Lipids 7 7 trace
Pigments 2 2 trace
Minerals 5 5 4.5
Phenolic compounds 30 5 4.5
Oxidized phenolics 0 25 4.5
Caffeine

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].

カフェイン

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]。

Caffeine Content in Beverages[11]
Product content (mg /150mL) Product content (mg /150mL)
espresso coffee 108-180 normal coffee 80-115
instant coffee 65 black tea (3min brew) 40-70
oolong tea 18-33 iced tea 29
green tea (3min brew) 15-25 cola soft drink 15-19
hot chocolate 4 cocoa milk shake 3
decaffeinated coffee 1-3 decaffeinated tea 0.6-3
plain chocolate 15 mg/20g milk chocolate 5 mg/20g
References
  1. ↑ 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. ↑ 2.0 2.1 USDA Database for the Flavonoid Contents of Selected Foods, Beltsville 2003
  3. ↑ 3.0 3.1 Wu CD, Wei GX (2002) "Tea as a functional food for oral health" Nutrition 18(5):443-444
  4. ↑ 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. ↑ 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. ↑ 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. ↑ 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
  8. ↑ Belitz DH, Grosch W (1997) "Quimica de los Alimentos" Zaragoza Acribia
  9. ↑ 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. ↑ 10.0 10.1 Varnam AH, Sutherland JP (1994) "Beverages: Technology, Chemistry and Microbiology" Chapman & Hall (London)
  11. ↑ 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
Prospective cohort 14873 men and 23667 women [3] → no association
Prospective cohort 11902 men and 14409 women [4] → no association
Prospective cohort 30370 men and 42481 women [5] → no association
Prospective cohort 18746 men and 26184 women [6] → no association
  • 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
  1. ↑ Borrelli F, Capasso R et al. (2004) "Systematic review: green tea and gastrointestinal cancer risk" Aliment Pharmacol Ther 19:497-510
  2. ↑ 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. ↑ 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
  4. ↑ Tsubono Y, Nishino Y et al. (2001) "Green tea and the risk of gastric cancer in Japan" New Engl J Med 344:632-636
  5. ↑ 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
  6. ↑ 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%.
At least, cocoa and soy (not tea) provide evidence for beneficial effects on CVD. However, it remains unclear whether the effects can be attributed to the specific flavonoid species[3]. A large scale cohort study (34789 men) found no association with flavonoids and CVD [4].


References
  1. ↑ Hertog MG, Feskens EJ (1993) "Dietary antioxidant flavonoids and risk of coronary heart disease: the Zutphen Elderly Study" Lancet 342(8878):1007-1011
  2. ↑ 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
  3. ↑ Geleijnse JM, Hollman PCH (2008) "Flavonoids and cardiovascular health: which compounds, what mechanisms?" Am J Clin Nutr 88:12-13
  4. ↑ 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
  1. ↑ Baur JA et al. Sinclair DA (2006) "Resveratrol improves health and survival of mice on a high-calorie diet" Nature 444:337-342
  2. ↑ Wu CH, Lu FH et al. (2003) "Relationship among habitual tea consumption, percent body fat, and body fat distribution" Obes Res 11:1088-1095
  3. ↑ 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
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