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==Classification of Tea <small>(茶の分類)</small>==
===Green Tea (緑茶)===
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It is non-fermented, i.e., produced by frying or steaming (fixation) the fresh leaves of [[Species:Camellia|''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.
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[[Species:Camellia|''Camellia sinensis''  var.''sinensis'']]の新鮮な茶葉を炒るか蒸して作られる非醗酵茶。加熱によりポリフェノール酸化酵素の働きを止めます(固定といいます）。日本で茶葉を蒸しますが、中国では炒るようです。アッサム茶（紅茶）に使われる''assamica''種はタンニンが多く緑茶には向きません。緑茶はそのほとんどが日本、ベトナム、中国、インドネシアのみで消費されます。
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===Black Tea (紅茶)===
{{Twocolumn|
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.
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緑茶と違い、摘んだ茶葉が萎れてから撚って細胞を破壊し、ポリフェノール酸化酵素を働かせます。インド、スリランカ、ケニヤの紅茶はCTC装置を使いますが、中国では旧式のローラーを使います。ローリングの後、茶葉は0.5-3時間25-35°C高湿度(>95%)で醗酵させます。フラボノイド成分が完全に酸化すると茶葉は黄金色になり芳香を持ちます。
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===Oolong Tea (烏龍茶)===
{{Twocolumn|
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.
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半醗酵茶です。茶葉を揺すって周辺部分を傷める摇青(yaoqing)作業と冷却する晾青(liangqing)を繰り返して作成します。良質のウーロン茶は周辺が赤っぽく、中央が緑色になります。ほとんどが中国の福建省、廣東省と台湾で生産されます。
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====Black Oolong Tea (黒烏龍茶)====
{{Twocolumn|Roasted oolong tea | 烏龍茶を焙煎しただけです。}}
====Golden-colored Oolong Tea (金色の烏龍茶)====
{{Twocolumn|Lightly fermented oolong tea. Often manufactured in Taiwan. | 醗酵程度の弱い烏龍茶です。台湾に多いタイプです。}}

===Pu-erh Tea (普洱茶)===
{{Twocolumn|
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.'' <ref>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</ref>
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.<ref>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</ref>
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自然状態のまま長期間（時に数十年）醗酵させる生茶と、より一般的な黒麹菌を植えて数ヶ月醗酵させた熟茶の二種があります。雲南省の熟茶の醗酵過程には''Aspergillus niger''（黒麹菌）を用いますが、他にも''A. gloucu'', ''Penicillium, Rhizopus, Saccharomyces, Bacterium''等が検出されます。黒麹の次に多く検出されるのは酵母の仲間です。熟茶は生茶に比べてカテキン類の含有量は減少しますが、カテキン等の分解産物としての没食子酸が増加します。抗酸化作用は生茶の方が有意に優れています。
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<references/>

==Tea Composition <small>(茶の組成)</small>==
{|
|- valign="top"
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;Catechins
The major phenolics in green tea include catechins (flavan 3-ols). They are [[FL63AGNS0001|(-)-epigallocatechin-3-gallate]] (EGCG; 59% of total catechins), [[FL63AGNS0003|(-)-epigallocatechin]] (EGC; 19%), [[FL63ACNS0006|(-)-epicatechin-3-gallate]] (ECG; 13.6%), and [[FL63ACNS0002|(-)-epicatechin]] (EC; 6.4%) <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>. Catechins are converted to theaflavins and thearubigins in black tea <ref name="USDA">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">Wu CD, Wei GX (2002) "Tea as a functional food for oral health" Nutrition 18(5):443-444</ref>, 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 <ref name="Kim">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</ref><ref name="Loktionov">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</ref>.

After drinking tea, the plasma level of catechins reach their peaks (between 1-10 &micro;mol/L) in 2 - 4 h <ref name="Yang">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 name="Higdon">Higdon JV, Frei B (2003) "Tea catechins and polyphenols: health effects, metabolism, and antioxidant functions" Crit Rev Food Sci Nutr 43:89-143</ref>.<br/>
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;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、[[FL63AGNS0001|(-)-エピガロカテキン-3-ガレート]] (EGCG; 全カテキンの59%), [[FL63AGNS0003|(-)-エピガロカテキン]] (EGC; 19%), [[FL63ACNS0006|(-)-エピカテキン-3-ガレート]] (ECG; 13.6%)そして[[FL63ACNS0002|(-)-エピカテキン]] (EC; 6.4%) <ref name="McKay"/>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<ref name="USDA"/>。
コップ１杯のお茶にはおよそ90 mgのEGCG <ref name="Wu"/>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<ref name="Kim"/><ref name="Loktionov"/>。

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 &micro;mol/L)に達します<ref name="Yang"/>。
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<ref name="Higdon"/>。
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{| class = "wikitable"
! colspan="4" | Major Composition (%)<ref>Belitz DH, Grosch W (1997) "Quimica de los Alimentos" Zaragoza Acribia</ref>
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! Compound || Green tea || Black tea || Black tea<br/>Infusion (3min)
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| Proteins || 15 || 15 || trace
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| Amino acids || 4 || 4 || 3.5
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| Fiber || 26 || 26 || 0
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| Others, carbohydrates || 7 || 7 || 4
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| Lipids || 7 || 7 || trace
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| Pigments || 2 || 2 || trace
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| Minerals || 5 || 5 || 4.5
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| Phenolic compounds || 30 || 5 || 4.5
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| Oxidized phenolics || 0 || 25 || 4.5
|}
|- valign="top"
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;Caffeine
The caffeine content in different types of tea is: black tea > oolong tea > gree tea > fresh tea leaf <ref name="Lin">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</ref>. More than 200 mg/day caffeine is not advisable and may produce nervousness, sleep disorders, vomits, headaches, epigastric pain, and tachycardia <ref name="Varnam">Varnam AH, Sutherland JP (1994) "Beverages: Technology, Chemistry and Microbiology" Chapman & Hall (London)</ref>.
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;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<ref name="Lin"/>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<ref name="Varnam"/>。
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{| class = "wikitable"
! colspan="4" | Caffeine Content in Beverages<ref name="Cabrera">Cabrera C, Artacho R, Gimenez R (2006) "Beneficial Effects of Green Tea-A Review" J Am Coll Nutr 25(2):79-99</ref>
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! Product || content <small>(mg /150mL)</small> || Product || content <small>(mg /150mL)</small>
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| espresso coffee || 108-180 || normal coffee         || 80-115
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| instant coffee  || 65      || black tea (3min brew) || 40-70
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| oolong tea      || 18-33   || iced tea              || 29
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| green tea (3min brew) || 15-25 || cola soft drink   || 15-19
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| hot chocolate   || 4       || cocoa milk shake || 3
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| decaffeinated coffee || 1-3|| decaffeinated tea || 0.6-3
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| plain chocolate || 15 mg/20g || milk chocolate || 5 mg/20g
|}
|}

;References
<references/>

==[[Doc:Tea/Consumption|Tea Production/Consumption <small>(茶の生産量、消費量)</small>]]==
==[[Doc:Tea/Health|Tea and Human Health <small>(健康情報)</small>]]==