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 Western World where black tea has been traditionally consumed.
Green tea has become the raw material for extracts used in various beverages, dietary supplements, and cosmetic items. 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.
Many claims have been made for the beneficial health effects of green tea consumption, but they have generally not been borne out by scientific investigation; excessive consumption is associated with some harmful health effects but moderate, regular consumption is safe.
- 1 History
- 2 Brewing and serving
- 3 Varieties of green tea
- 4 Research and health effects
- 5 Production
- 6 See also
- 7 References
- 8 Further reading
- 9 External links
Tea consumption has its legendary origins in China dating back to more than 4,000 years ago, making it the oldest herbal tea known. Green tea was first brewed in 2737 BC during the reign of Emperor Shennong.
A book written by Lu Yu in 600-900 AD (Tang Dynasty), "Tea Classic" (simplified Chinese: 茶经; traditional Chinese: 茶經; pinyin: chájīng), is considered important in green tea history. The Kissa Yojoki (喫茶養生記 Book of Tea), written by Zen priest Eisai in 1191, describes how drinking green tea may affect five vital organs, the shapes of tea plants, flowers and leaves, and how to grow and process tea leaves.
Brewing and serving
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. 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
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Chinese green tea
Green tea is the most popular form of tea in China. Chinese green teas are made from over 600 different cultivars of the camellia sinensis plant, giving plenty of variety and regional teas. Chinese green teas are traditionally pan-fired, unlike the Japanese steaming process. Other processes in China include oven-dried and sun-dried. Due to the different production process, Chinese teas are said to have a more "earthy" taste than Japanese teas.
- 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.
- 龙井 Longjing
- 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-fired and has a distinctive flat appearance. The tasteless frying oil is obtained from tea seeds and other plants. There are many fake Longjings on the market and in less-scrupulous teahouses around the country.
- 景宁惠明茶 Huiming
- Named after a temple in Zhejiang.
- 开化龙顶 Kaihua Longding
- A tea from Kaihua County known as Dragon Mountain.
- 华顶云雾 Hua Ding
- A tea from Tiantai County, named after a peak in the Tiantai mountain range.
- 天目青顶 Qing Ding
- A tea from Tian Mu, also known as Green Top.
- 平水珠茶 Gunpowder
- Jiangsu Province
- 洞庭碧螺春 Bi Luo Chun
- 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.
- 南京雨花茶 Rain Flower
- A tea from Nanjing.
- originate in Jin Tan city of Jiangsu Province.
- 太湖白云 White Cloud
- 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.
- 茉莉花茶 Jasmine tea (Mo Li Hua Cha)
- A tea with added jasmine flowers.
- 毛峰 Mao Feng tea
- Meaning "furry peak".
- 翠剑 Cui Jian
- Meaning "jade sword".
- Hubei Province
- Henan Province
- Jiangxi Province
- 珍眉 Chun Mee
- 狗牯 Gou Gu Nao
- A well-known tea within China and recipient of numerous national awards.
- 云雾 Yun Wu
- A tea also known as Cloud and Mist.
- 大方 Da Fang
- A tea from Huangshan also known as Big Square suneet.
- 黄山毛峰 Huangshan Maofeng
- A Chinese famous tea from Huangshan
- 六安瓜片 Liuan Leaf
- A Chinese famous tea also known as Melon Seed
- 猴魁 Hou Kui
- A Chinese famous tea also known as Monkey tea
- 屯绿 Tun Lu
- A tea from Tunxi District.
- 火青 Huo Qing
- A tea from Jing County, also known as Fire Green
- 雾里青 Wuliqing
- 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.
- Sichuan Province
- 竹叶青茶 Zhu Ye Qing
- Also known as Meng Ding Cui Zhu or Green Bamboo
- 蒙顶甘露 Meng Ding Gan Lu
- A yellowish-green tea with sweet aftertaste.
- 百美绿茶 Baimei Green Tea
- Shaanxi Province
- 汉中仙毫 Han Zhong Xian Hao
- A green tea from the Han Zhong.
Japanese green tea
Green tea (緑茶 Ryokucha?) is ubiquitous in Japan and is commonly known simply as "tea" (お茶 ocha?). Tea was first used in China, and was brought to Japan by Myōan Eisai, a Japanese Buddhist priest who also introduced the Rinzai school of Zen Buddhism. Teas from Japan may be referred to as "Japanese tea" (日本茶 nihoncha?).
Japanese green tea is made from the Yabukita (薮北?) cultivar of the camellia sinensis plant. Unlike Chinese green teas which are pan-fired, Japanese green teas are steamed giving them a more "vegetative" or "leafy" taste. The exception is hōjicha, a Japanese roasted tea. Japanese green teas are categorized by the age of the leaves: young leaves are called sench and the more mature, larger leaves are called bancha. Types of tea are commonly graded depending on the quality and the parts of the plant used as well as how they are processed. There are large variations in both price and quality within these broad categories, and there are many green teas that fall outside this spectrum. The best Japanese green tea is said to be from the Yame (八女 yame?) region of Fukuoka Prefecture and from the Uji region of Kyoto. Uji has been producing Ujicha (Uji tea) for four hundred years, predating the prefectural system. It is now a combination of the border regions of Shiga, Nara, Kyoto, and Mie prefectures. Shizuoka Prefecture produces 40 percent 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.
- 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. 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. 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 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.
- 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.
- Half-finished products used for Sencha and Gyokuro production. It contains all parts of the tea plant.
- 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
Research and health effects
Green tea contains a variety of enzymes, amino acids, carbohydrates, lipids, sterols, related compounds, dietary minerals, and phytochemicals such as polyphenols, flavanols, and caffeine. Polyphenols found in green tea include but are not limited to epigallocatechin gallate (EGCG), epigallocatechin, epicatechin gallate, and epicatechin; flavanols such as kaempferol, quercetin, and myricitin are also found in green tea. Numerous claims have been made for the health benefits of green tea based on its chemical composition, in vitro studies, animal studies, and human epidemiological studies. Preliminary research on many of these claims is promising, but many also require further study to evaluate. In 2011 a panel of scientists published a report on green tea's claimed health effects at the request of the European commission: in general they found that the claims made for green tea were not supported by good scientific evidence. Although the mean content of flavonoids and catechins 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 promote health, flavonoids and catechins have no proven biological effect in humans.
There is no conclusive evidence that green tea helps to prevent or treat cancer in people. A review of existing studies concluded that while suggestive evidence existed, it did not amount to a clear indication of benefit.
Meta-analyses in 2014 found limited evidence that green tea consumption may be associated with a slightly lower risk of esophageal cancer in the Chinese population, a lower risk of lung cancer in women, and a lower risk of oral cancer in Asian people. Another analysis of observational data conducted in 2012 suggested that green tea consumption may have a favorable effect on lung cancer risk. The observed effect was strongest in those who consumed more than seven cups of green tea daily. In 2011, a meta-analysis of epidemiological studies found limited evidence that green tea consumption may be associated with a moderately reduced risk of liver cancer in Chinese and Japanese people.
In contrast, separate 2014 meta-analyses found limited evidence that green tea consumption is not associated with the risk of developing pancreatic cancer or prostate cancer. The link between green tea consumption and stomach cancer risk is unclear due to inconsistent evidence.
Green tea consumption may be associated with a reduced risk of stroke. A 2013 Cochrane review of randomized controlled trials concluded that green tea consumption for 3–6 months appears to lower systolic and diastolic blood pressures a small amount (about 3 mmHg each). Additional analyses examining the effects of long-term green tea consumption on blood pressure have reached similar conclusions.
A 2011 meta-analysis of 14 short-term randomized controlled trials concluded that consumption of green tea or green tea supplements decreases the blood concentration of total cholesterol (about 7 mg/dL), LDL cholesterol (about 2 mg/dL), and had no effect on the concentration of HDL cholesterol. A 2013 Cochrane review performed a meta-analysis of longer-term randomized controlled trials (>3 months duration) and concluded that green tea consumption lowers total and LDL cholesterol concentrations in the blood.
Moderate, regular, and habitual consumption of green tea is safe; however, there are reports of liver toxicity in humans after consuming high doses (10–29 mg/kg/day) of green tea extract dietary supplements. High doses of epigallocatechin gallate (EGCG), an abundant catechin found in green tea, have also been found to cause oxidative stress in mice and in vitro.
Growing, harvesting and processing
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. Sun-drying, basket or charcoal firing, or pan-firing are common artisanal methods. Oven-drying, tumbling, or steaming are common modern methods. Processed green teas, known as aracha are stored under low humidity refrigeration in 30- or 60-kilogram 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.
Production by country
|2006 Green tea production and export (in thousands of metric tons)
Import of Japanese tea
On 17 June 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 the tea leaves, which amounted to 162 kilograms (357 lb). 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. Minister for Consumer Affairs and Food Safety Renhō stated on 3 June 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."
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|Wikimedia Commons has media related to Green tea.|
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