Green tea

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This article is about the type of tea. For other uses, see Green Tea (disambiguation).
The appearance of green tea in three different stages (from left to right): the infused leaves, the dry leaves, and the liquid. Notice that the infused leaves look greener than the dry leaves.
The tea fields in the foothills of Gorreana, Azores Islands, Portugal: the only European region other than Georgia to support green tea production.

Green tea is made from the leaves from Camellia sinensis that have undergone minimal oxidation during processing. Green tea originated in China, but it has become associated with many cultures throughout Asia. Green tea has recently become relatively widespread in the West where black tea has been the traditionally consumed tea. Green tea has become the raw material for extracts used in various beverages, health foods, dietary supplements, and cosmetic items.[1] Many varieties of green tea have been created in the countries where it is grown. These varieties can differ substantially due to variable growing conditions, horticulture, production processing, and harvesting time.

Over the last few decades green tea has been subjected to numerous scientific and medical studies to determine the extent of its long-purported health benefits, with some evidence suggesting that regular green tea drinkers may have a lower risk of developing heart disease and certain types of cancer.[2] Although green tea does not raise the metabolic rate enough to produce immediate weight loss, a green tea extract containing polyphenols and caffeine has been shown to induce thermogenesis and stimulate fat oxidation, boosting the metabolic rate 4% without increasing the heart rate.[3]

The mean content of flavonoids in a cup of green tea is higher than that in the same volume of other food and drink items that are traditionally considered to be of health contributing nature, including fresh fruits, vegetable juices or wine.[4] Flavonoids are a group of phytochemicals present in most plant products that are responsible for health benefits such as anti-oxidative and anticarcinogenic functions.[4] However, the content of flavonoids may vary dramatically amongst different tea products.

History[edit]

Main article: History of tea

Tea consumption has its legendary origins in China dating back to more than 4,000 years ago, making it the oldest herbal tea known to man. Green tea was first brewed in 2737 BC during the reign of Emperor Shennong.[5] Green tea has been used as both a beverage and a medicine in most of Asia, including China, Japan, Thailand, and Vietnam, to help everything from controlling bleeding and helping heal wounds to regulating body temperature, blood sugar and promoting digestion.

A book written in the Tang Dynasty of China is considered one of the most important in the history of green tea. The book was written by Lu Yu and is called the "Tea Classic" (simplified Chinese: ; traditional Chinese: ; pinyin: chájīng). It was written between 600 and 900 AD and spoke about exactly how and where one could enjoy a fine cup of green tea. The Kissa Yojoki (喫茶養生記 Book of Tea), written by Zen priest Eisai in 1191, describes how drinking green tea can have a positive effect on the five vital organs, especially the heart. The book discusses tea's supposed medicinal qualities, which include easing the effects of alcohol, acting as a stimulant, curing blotchiness, quenching thirst, eliminating indigestion, curing beriberi disease, preventing fatigue, and improving urinary and brain function. Part One also explains the shapes of tea plants, tea flowers, and tea leaves, and covers how to grow tea plants and process tea leaves. In Part Two, the book discusses the specific dosage and method required for individual physical ailments.

Brewing and serving[edit]

Green tea leaves steeping in a gaiwan

Steeping is the process of making a cup of tea; it is also referred to as brewing. In general, two grams of tea per 100 ml of water, or about one teaspoon of green tea per five-ounce (150 ml) cup, should be used. With very high-quality teas like gyokuro, more than this amount of leaf is used, and the leaf is steeped multiple times for short durations.

Green tea steeping time and temperature varies with different tea. The hottest steeping temperatures are 81 to 87 °C (178 to 189 °F) water and the longest steeping times two to three minutes. The coolest brewing temperatures are 61 to 69 °C (142 to 156 °F) and the shortest times about 30 seconds. In general, lower-quality green teas are steeped hotter and longer, whereas higher-quality teas are steeped cooler and shorter. Steeping green tea too hot or too long will result in a bitter, astringent brew, regardless of the initial quality, because it will result in the release of an excessive amount of tannins.[6] High-quality green teas can be and usually are steeped multiple times; two or three steepings is typical. The steeping technique also plays a very important role in avoiding the tea developing an overcooked taste. The container in which the tea is steeped or teapot should also be warmed beforehand so that the tea does not immediately cool down. It is common practice for tea leaf to be left in the cup or pot and for hot water to be added as the tea is drunk until the flavor degrades.

Varieties of green tea[edit]

Chinese green tea[edit]

  • Zhejiang Province is home to the most famous of all teas, Xi Hu Longjing (西湖龙井), as well as many other high-quality green teas.
Maybe the most well-known green tea in China; originates from Hangzhou (杭州), the capital of Zhejiang Province. Longjing in Chinese literally means dragon well. It is pan-fried and has a distinctive flat appearance. The tasteless frying oil is obtained from tea seeds and other plants. Most of the tea on the market is in fact produced in Sichuan Province[citation needed] and, hence, is not authentic Longjing, despite many tea producers' claims.
Named after a temple in Zhejiang
A tea from Kaihua County known as Dragon Mountain
A tea from Tiantai County, named after a peak in the Tiantai mountain range
A tea from Tian Mu, also known as Green Top
A popular tea also known as zhuchá, originates in Zhejiang but is now grown elsewhere in China. This tea is also the quintessential ingredient in brewing Moroccan green tea with fresh mint.
A plate of Bi Luo Chun tea, from Jiangsu Province in China
A Chinese famous tea also known as Green Snail Spring, from Dong Ting. As with Longjing, inauthentic Bi Luo Chun is common and most of the tea marketed under this name may, in fact, be grown in Sichuan.
A tea from Nanjing.
originate in Jin Tan city of Jiangsu Province.
Camellia sinensis, the tea plant
  • Fujian Province is known for mountain-grown organic green tea as well as white tea and oolong tea. The coastal mountains provide a perfect growing environment for tea growing. Green tea is picked in spring and summer seasons.
A tea with added jasmine flowers.
Meaning "furry peak".
  • 翠剑 Cui Jian
Meaning "jade sword".
A steamed tea also known as Gyokuro (Jade Dew) in Japanese, made in the Japanese style.
An example of a Chinese green tea, called Mao Jian.
A Chinese famous tea also known as Green Tip, or Tippy Green.
Meaning "precious eyebrows"; from Jiangxi, it is now grown elsewhere.
A well-known tea within China and recipient of numerous national awards.
A tea also known as Cloud and Mist.
A tea from Huangshan also known as Big Square suneet.
A Chinese famous tea from Huangshan
A Chinese famous tea also known as Melon Seed
A Chinese famous tea also known as Monkey tea
A tea from Tunxi District.
A tea from Jing County, also known as Fire Green
Wuliqing was known since the Song dynasty. Since 2002, Wuliqing is produced again according to the original processing methods by a company called Tianfang (天方). Zhan Luojiu a tea expert and professor at the Anhui Agricultural University who relived its production procedure.
A medium-quality tea from many provinces, an early-harvested tea.
Also known as Meng Ding Cui Zhu or Green Bamboo
A yellowish-green tea with sweet aftertaste.
  • 百美绿茶 Baimei Green Tea
A green tea from the Han Zhong.

Japanese green tea[edit]

Japanese green tea
Genmaicha
Aracha

Green tea (緑茶 Ryokucha?) is ubiquitous in Japan and therefore is more commonly known simply as "tea" (お茶 ocha?). It is even referred to as "Japanese tea" (日本茶 nihoncha?), though it was first used in China during the Song Dynasty, and brought to Japan by Myōan Eisai, a Japanese Buddhist priest who also introduced the Rinzai school of Zen Buddhism.

Types of tea are commonly graded depending on the quality and the parts of the plant used as well as how they are processed.[7] There are large variations in both price and quality within these broad categories, and there are many specialty green teas that fall outside this spectrum. The best Japanese green tea is said to be that from the Yame (八女 yame?) region of Fukuoka Prefecture and the Uji region of Kyoto. The so-called Uji area has been producing Ujicha (Uji tea) for four hundred years and predates the prefectural system. It is now a combination of the border regions of Shiga, Nara, Kyoto, and Mie prefectures. Sōraku District, Kyoto is among many of the tea producing districts.[citation needed] Shizuoka Prefecture produces 40% of raw tea leaf.

The first and second flushes of green tea made from leaves that are exposed directly to sunlight. This is the most common green tea in Japan. The name describes the method for preparing the beverage.
  • Fukamushicha (深蒸し茶?, long-steamed green tea)
Sencha, which, in the processing of the leaves, has been steamed two times longer than usual Sencha, giving it a deeper color and producing a fuller flavor in the beverage.
Gyokuro is a fine and expensive type that differs from Sencha (煎茶) in that it is grown under the shade rather than the full sun for approximately 20 days.[8] The name "Gyokuro" translates as "jade dew" and refers to the pale green color of the infusion. The shading causes the amino acids (Theanine) and caffeine in the tea leaves to increase, while catechins (the source of bitterness in tea, along with caffeine) decreases, giving rise to a sweet taste.[9] The tea also has a distinct aroma.
Kabusecha is made from the leaves grown in the shade prior to harvest, although not for as long as Gyokuro. It has a more delicate flavor than Sencha. It is sometimes marketed as Gyokuro.
Tamaryokucha has a tangy, berry-like taste, with a long almondy aftertaste and a deep aroma with tones of citrus, grass, and berries. It is also called Guricha.
Lower grade of Sencha harvested as a third- or fourth-flush tea between summer and autumn. Aki-Bancha (autumn Bancha) is not made from entire leaves, but from the trimmed unnecessary twigs of the tea plant.
Kamairicha is a pan-fired green tea that does not undergo the usual steam treatments of Japanese tea and does not have the characteristic bitter taste of most Japanese tea.
  • By-product of Sencha or Gyokuro
A tea made from stems, stalks, and twigs. Kukicha has a mildly nutty, and slightly creamy sweet flavor.
  • Mecha (芽茶?, buds and tips tea)
Mecha is green tea derived from a collection of leaf buds and tips of the early crops. Mecha is harvested in spring and made as rolled leaf teas that are graded somewhere between Gyokuro and Sencha in quality.
  • Konacha (粉茶?, (coarse) powdered tea)
Konacha is the dust and smallest parts after processing Gyokuro or Sencha. It is cheaper than Sencha and usually served at Sushi restaurants. It is also marketed as Gyokuroko (玉露粉?) or Gyokurokocha.
  • Other
A fine ground tea made from Tencha. It has a very similar cultivation process as Gyokuro. It is expensive and is used primarily in the Japanese tea ceremony. Matcha is also a popular flavor of ice cream and other sweets in Japan.
  • Tencha ( 碾茶?, milling tea)
Half-finished products used for Matcha production. The name indicates its intended eventual milling into matcha. Because, like gyokuro, it is cultivated in shade, it has a sweet aroma. In its processing, it is not rolled during drying, and tencha, therefore, remains spread out like the original fresh leaf.
Bancha (sometimes Sencha) and roasted genmai (brown rice) blend. It is often mixed with a small amount of Matcha to make the color better.
A green tea roasted over charcoal (usually Bancha).
Half-finished products used for Sencha and Gyokuro production. It contains all parts of the tea plant.
First flush tea. The name is used for either Sencha or Gyokuro.
  • funmatsucha (粉末茶?, instant powdered tea)
Milled green tea, used just like instant coffee. Another name for this recent style of tea is "tokeru ocha," or "tea that melts."

Other green teas[edit]

Research and health effects[edit]

Main article: Health effects of tea

Green tea contains a variety of enzymes, amino acids, carbohydrates, lipids, sterols, related compounds, phytochemicals, and dietary minerals. Numerous claims have been made for the health benefits of green tea based on chemical composition, in vitro and animal studies, and while preliminary research on many of these claims is promising, many also require further study to evaluate.[10][11] There is also evidence suggesting consuming large volumes of green tea, and in particularly green tea extracts, may cause oxidative stress and liver toxicity.[12]

There is no good evidence that green tea helps to prevent or treat cancer in people.[11][13]

Green tea may interfere with the anti-cancer drug bortezomib (Velcade) and other boronic acid-based proteasome inhibitors.[14][15]

Production[edit]

Growing, harvesting and processing[edit]

Hand rolling green tea after steaming

Green tea is processed and grown in a variety of ways, depending on the type of green tea desired. As a result of these methods, maximum amounts of polyphenols and volatile organic compounds are retained, affecting aroma and taste. The growing conditions can be broken down into two basic types — those grown in the sun and those grown under the shade. The green tea plants are grown in rows that are pruned to produce shoots in a regular manner, and in general are harvested three times per year. The first flush takes place in late April to early May. The second harvest usually takes place from June through July, and the third picking takes place in late July to early August. Sometimes, there will also be a fourth harvest. It is the first flush in the spring that brings the best-quality leaves, with higher prices to match.

Green tea is processed using either artisanal or modern methods.[16] Sun-drying, basket or charcoal firing, or pan-firing are common artisanal methods.[16] Oven-drying, tumbling, or steaming are common modern methods.[16] Processed green teas, known as "aracha" are stored under low humidity refrigeration in 30- or 60-kg paper bags at 0–5 °C (32–41 °F). This aracha has yet to be refined at this stage, with a final firing taking place before blending, selection, and packaging takes place. The leaves in this state will be re-fired throughout the year as they are needed, giving the green teas a longer shelf-life and better flavor. The first flush tea of May will readily store in this fashion until the next year's harvest. After this re-drying process, each crude tea will be sifted and graded according to size. Finally, each lot will be blended according to the blend order by the tasters and packed for sale.[17]

Production by country[edit]

2006 Green tea production and export (in thousands of metric tons)[18]
Country Production Export
 China 782.4 (80.8%) 218.7 (83.0%)
 Japan 91.8 (9.5%) 1.6 (0.6%)
 Vietnam 66.0 (6.8%) 26.0 (9.9%)
 Indonesia 20.0 (2.1%) 9.1 (3.5%)
World 968.1 (100%) 263.5 (100%)

Import of Japanese tea[edit]

On June 17, 2011, radioactive cesium of 1,038 becquerels per kilogram was detected at Charles de Gaulle airport in France in tea leaves imported from Shizuoka Prefecture, Japan, which was more than twice as much as the restricted amount of 500 becquerels per kilogram designated by the European Union, and the government of France announced that they rejected them, which amounted to 162 kg (357 lb).[19] The governor of Shizuoka Prefecture Heita Kawakatsu stated that "there is absolutely no problem when they [people] drink them because it will be diluted to about ten becquerels per kilogram when they steep them even if the leaves have 1,000 becquerels per kilogram," which was a consequence of own examinations of the prefecture.[20] Minister for Consumer Affairs and Food Safety Renhō stated on June 3, 2011, that "there are cases in which aracha are sold as furikake [condiments sprinkled on rice] and so on and they are eaten as they are, therefore we think that it is important to inspect tea leaves including aracha from the viewpoint of consumers' safety."[21]

See also[edit]

References[edit]

  1. ^ Reich, Eike; Anne Schibil, Valeria Widmer, Ruth Jorns, Evelyn Wolfram, Alison DeBatt (August 2006), HPTLC methods for identification of green tea and green tea extract, Journal of Liquid Chromatography & Related Technologies 29 (14): 2141–2151, doi:10.1080/15512160600760293 
  2. ^ Green tea's cancer-fighting allure becomes more potent, sciencedaily.com, 2003 
  3. ^ Dulloo AG, Duret C, Rohrer D, Girardier L, Mensi N, Fathi M, Chantre P, Vandermander J (1999), Efficacy of a green tea extract rich in catechin polyphenols and caffeine in increasing 24-h energy expenditure and fat oxidation in humans, Am. J. Clin. Nutr. 70 (6): 1040–5, PMID 10584049 
  4. ^ a b USDA Database for the Flavonoid Content of Selected Foods, Release 2.1 (2007)
  5. ^ Dattner, Christine; Boussabba, Sophie (2003), Emmanuelle Javelle, ed., The Book of Green Tea, Universe Books, p. 13, ISBN 978-0-7893-0853-5, retrieved 24 March 2013 
  6. ^ However, when using green tea medicinally, this is purposely done for treating acute diarrhea or chronic indigestion. A quart or so of the tea is simmered for half an hour or more and the resulting brew is sipped slowly throughout the day. Stefan Chmelik, "Chinese Herbal Secrets: The Key to Total Health." Avery Publishing Group, 1999. pg. 143.
  7. ^ Heiss, Mary Lou; Heiss, Robert J. (2007), The Story of Tea: A Cultural History and Drinking Guide, Ten Speed Press, pp. 179–185, ISBN 1-58008-745-0 
  8. ^ Illustrated explanation of the process for producing gyokuro tea, Ippodo-tea.co.jp, retrieved 2013-01-13 
  9. ^ About the effects of the shading process, and the components of this tea compared to others, Ippodo-tea.co.jp, retrieved 2013-01-13 
  10. ^ Cabrera C, Artacho R, Giménez R (April 2006), Beneficial Effects of Green Tea--A Review, J Am Coll Nutr 25 (2): 79–99, doi:10.1080/07315724.2006.10719518, PMID 16582024 
  11. ^ a b Boehm K, Borrelli F, Ernst E, et al. (2009). "Green tea (Camellia sinensis) for the prevention of cancer". Cochrane Database Syst Rev (Systematic review) (3): CD005004. doi:10.1002/14651858.CD005004.pub2. PMID 19588362. 
  12. ^ Lambert JD, Sang S, Yang CS (April 2007), Possible controversy over dietary polyphenols: benefits vs risks, Chem. Res. Toxicol. 20 (4): 583–5, doi:10.1021/tx7000515, PMID 17362033 
  13. ^ Johnson R, Bryant S, Huntley AL (December 2012). "Green tea and green tea catechin extracts: an overview of the clinical evidence". Maturitas (Review) 73 (4): 280–7. doi:10.1016/j.maturitas.2012.08.008. PMID 22986087. 
  14. ^ Golden, EB; Lam, P. Y.; Kardosh, A.; Gaffney, K. J.; Cadenas, E.; Louie, S. G.; Petasis, N. A.; Chen, T. C.; Schonthal, A. H. (2009), Green tea polyphenols block the anticancer effects of bortezomib and other boronic acid-based proteasome inhibitors, Blood 113 (23): 5927–37, doi:10.1182/blood-2008-07-171389, PMID 19190249 
  15. ^ "Green tea clash with bortezomib suggested". Retrieved 26 July 2013. 
  16. ^ a b c Heiss, Mary Lou; Heiss, Robert J. (2007), Hardcover, ed., The Story of Tea: A Cultural History and Drinking Guide, Ten Speed Press, pp. 56–69, ISBN 978-1-60774-172-5 
  17. ^ Green Tea Processing, O-cha.com, retrieved 2013-01-13 
  18. ^ Current situation and medium-term outlook, Intergovernmental Group on Tea, UN Food and Agriculture Organization, May 2008, p. 9 
  19. ^ "日本からの緑茶に基準超えるセシウム パリの空港で検出." (Japanese) Asahi Shimbun. 2011-06-18. Retrieved 2011-06-19.
  20. ^ "静岡知事「飲用茶にすれば問題ない」 仏での検出受け." (Japanese) Asahi Shimbun. 2011-06-18. Retrieved 2011-06-19.
  21. ^ "蓮舫内閣府特命担当大臣記者会見要旨(平成23年6月3日(金))." (Japanese) Consumer Affairs Agency. 2011-06-03. Retrieved 2011-06-19.

Further reading[edit]

  • Evans, John C. Tea in China: The History of China's National Drink. Greenwood Press, 1992. ISBN 978-0-313-28049-8
  • Lam, K.C./Lam, K.S. The Way of Tea: The Sublime Art of Oriental Tea Drinking. Barron's Educational Series, 2002. ISBN 978-0-7641-1968-2

External links[edit]