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Tea
Longjing green tea being infused in a gaiwan
TypeHot or cold beverage
OriginChina[1]
IntroducedFirst recorded in China in 59 BC, possibly originated earlier[2]

Tea is an aromatic beverage prepared by pouring hot or boiling water over cured or fresh leaves of Camellia sinensis, an evergreen shrub native to East Asia which originated in the borderlands of south-western China and northern Myanmar.[3][4][5] Tea is also made, but rarely, from the leaves of Camellia taliensis and Camellia formosensis.[6][7][8][9] After plain water, tea is the most widely consumed drink in the world.[10] There are many types of tea; some have a cooling, slightly bitter, and astringent flavour, while others have profiles that include sweet, nutty, floral, or grassy notes.[11] Tea has a stimulating effect in humans, primarily due to its caffeine content.[12]

An early credible record of tea drinking dates to the third century AD, in a medical text written by Chinese physician Hua Tuo.[13] It was popularised as a recreational drink during the Chinese Tang dynasty, and tea drinking spread to other East Asian countries. Portuguese priests and merchants introduced it to Europe during the 16th century.[14] During the 17th century, drinking tea became fashionable among the British, who later started to plant tea on a large scale in India, where it had previously been used only as a medicine.

The term herbal tea refers to drinks not made from Camellia sinensis. They are the infusions of fruit, leaves, or other plant parts, such as steeps of rosehip, chamomile, or rooibos. These may be called tisanes or herbal infusions to prevent confusion with tea made from the tea plant.

Etymology

[edit]
Main article: Etymology of tea

The etymology of the various words for tea reflects the history of transmission of tea drinking and trade from China.[15] Nearly all of the words for tea worldwide fall into three broad groups: te, cha and chai, present in English as tea, cha or char, and chai. The earliest of the three to enter English is cha, which came in the 1590s via the Portuguese, who traded in Macao and picked up the Cantonese pronunciation of the word.[16][17] The more common tea form arrived in the 17th century via the Dutch, who acquired it either indirectly from the Malay teh, or directly from the tê pronunciation in Min Chinese.[16] The third form chai (meaning "spiced tea") originated from a northern Chinese pronunciation of cha, which travelled overland to Central Asia and Persia where it picked up a Persian ending yi. The Chinese word for tea itself was perhaps derived from the non-Sinitic languages of the botanical homeland of the tea plant in south-west China (or Burma), possibly from an archaic Austro-Asiatic root word *la, meaning "leaf".[18]

Origin and history

[edit]

Botanical origin

[edit]
Further information: History of tea and History of tea in China
Tea plant (Camellia sinensis) from Köhler's Medicinal Plants, 1897

Tea plants are native to East Asia and the probable center of origin of tea is near the source of the Irrawaddy River from where it spread out fan-wise into southeast China, Indo-China and Assam. The natural home of the tea plant is considered to be within the comparatively small fan-shaped area between Nagaland, Manipur and Mizoram along the Burma frontier in the west, through China as far as the Zhejiang Province in the east, and from this line generally south through the hills to Burma and Thailand to Vietnam. The west–east axis indicated above is about 2,400 km long extending from longitude 95°-120°E. The north–south axis covers about 1,920 km, starting from the northern part of Burma, latitude 29°N passing through Yunnan, Tongkin, Thailand, Laos and on to Annan, reaching latitude 11°N.[19]

Chinese (small-leaf) type tea (C. sinensis var. sinensis) may have originated in southern China possibly with hybridization of unknown wild tea relatives. Since there are no known wild populations of this tea, its origin is speculative.[20][21]

Given their genetic differences forming distinct clades, Chinese Assam-type tea (C. sinensis var. assamica) may have two parentages – one being found in southern Yunnan (Xishuangbanna, Pu'er City) and the other in western Yunnan (Lincang, Baoshan). Many types of Southern Yunnan Assam tea have been hybridized with the closely related species Camellia taliensis. Unlike Southern Yunnan Assam tea, Western Yunnan Assam tea shares many genetic similarities with Indian Assam-type tea (also C. sinensis var. assamica). Thus, Western Yunnan Assam tea and Indian Assam tea both may have originated from the same parent plant in the area where southwestern China, Indo-Burma, and Tibet meet. However, as the Indian Assam tea shares no haplotypes with Western Yunnan Assam tea, Indian Assam tea is likely to have originated from an independent domestication. Some Indian Assam tea appears to have hybridized with the species Camellia pubicosta.[20][21]

Assuming a generation of 12 years, Chinese small-leaf tea is estimated to have diverged from Assam tea around 22,000 years ago, while Chinese Assam tea and Indian Assam tea diverged 2,800 years ago. The divergence of Chinese small-leaf tea and Assam tea would correspond to the last glacial maximum.[20][21]

Early tea drinking

[edit]
A 19th-century Japanese painting depicting Shennong: Chinese legends credit Shennong with the invention of tea.[22]

People in ancient East Asia ate tea for centuries, perhaps even millennia, before ever consuming it as a beverage. They would nibble on the leaves raw, add them to soups or greens, or ferment them and chew them as areca nut is chewed.[23]

Tea drinking may have begun in the region of Yunnan, where it was used for medicinal purposes. It is believed that in Sichuan, "people began to boil tea leaves for consumption into a concentrated liquid without the addition of other leaves or herbs, thereby using tea as a bitter yet stimulating drink, rather than as a medicinal concoction."[5]

Chinese legends attribute the invention of tea to the mythical Shennong (in central and northern China) in 2737 BC, although evidence suggests that tea drinking may have been introduced from southwest China.[22] The earliest written records of tea come from China. The word tú 荼 appears in the Shijing and other ancient texts to signify a kind of "bitter vegetable" (苦菜), and it is possible that it referred to many different plants such as sow thistle, chicory, or smartweed,[24] as well as tea.[25] In the Chronicles of Huayang, it was recorded that the Ba people in Sichuan presented tu to the Zhou king. The Qin later conquered the state of Ba and its neighbour Shu, and according to the 17th century scholar Gu Yanwu who wrote in Ri Zhi Lu (日知錄): "It was after the Qin had taken Shu that they learned how to drink tea."[2] Another possible early reference to tea is found in a letter written by the Qin dynasty general Liu Kun who requested that some "real tea" to be sent to him.[26]

The earliest known physical evidence[27] of tea was discovered in 2016 in the mausoleum of Emperor Jing of Han in Xi'an, indicating that tea from the genus Camellia was drunk by Han dynasty emperors as early as the second century BC.[28] The Han dynasty work "The Contract for a Youth", written by Wang Bao in 59 BC,[29] contains the first known reference to boiling tea. Among the tasks listed to be undertaken by the youth, the contract states that "he shall boil tea and fill the utensils" and "he shall buy tea at Wuyang".[2] The first record of tea cultivation is dated to this period, during which tea was cultivated on Meng Mountain (蒙山) near Chengdu.[30] Another early credible record of tea drinking dates to the 3rd century AD, in a medical text by the Chinese physician Hua Tuo, who stated, "to drink bitter t'u constantly makes one think better."[31] However, before the Tang dynasty, tea-drinking was primarily a southern Chinese practice centered in Jiankang.[32] Tea was disdained by the Northern dynasties aristocrats, who describe it as inferior to yogurt.[33][34] It became widely popular during the Tang dynasty, when it spread to Korea, Japan, and Vietnam. The Classic of Tea, a treatise on tea and its preparations, was written by the 8th century Chinese writer, Lu Yu. He was known to have influenced tea drinking on a large part in China.[35]

Developments

[edit]
Tea with ingredients, China

Through the centuries, a variety of techniques for processing tea, and a number of different forms of tea, were developed. During the Tang dynasty, tea was steamed, then pounded and shaped into cake form,[36] while in the Song dynasty, loose-leaf tea was developed and became popular. During the Yuan and Ming dynasties, unoxidized tea leaves were first stirred in a hot dry pan, then rolled and air-dried, a process that stops the oxidation process that would have turned the leaves dark, thereby allowing tea to remain green. In the 15th century, oolong tea, in which the leaves are allowed to partially oxidize before being heated in the pan, was developed.[32] Western tastes, however, favoured the fully oxidized black tea, and the leaves were allowed to oxidize further. Yellow tea was an accidental discovery in the production of green tea during the Ming dynasty, when apparently careless practices allowed the leaves to turn yellow, which yielded a different flavour.[37]

Worldwide spread

[edit]
See also: Arabic tea, Korean tea, Tea in Australia, and Tea in France
Tea-weighing station north of Batumi, Russian Empire, before 1915

Tea was first introduced to Western priests and merchants in China during the 16th century, at which time it was termed chá.[14] The earliest European reference to tea, written as chiai, came from Delle navigationi e viaggi written by Venetian Giambattista Ramusio in 1545.[38] The first recorded shipment of tea by a European nation was in 1607 when the Dutch East India Company moved a cargo of tea from Macao to Java, then two years later, the Dutch bought the first assignment of tea which was from Hirado in Japan to be shipped to Europe.[39] Tea became a fashionable drink in The Hague in the Netherlands, and the Dutch introduced the drink to Germany, France, and across the Atlantic to New Amsterdam (New York).[40]

In 1567, Russian people came in contact with tea when the Cossack Atamans Petrov and Yalyshev visited China.[41] The Mongolian Khan donated to Tsar Michael I four poods (65–70 kg) of tea in 1638.[42] According to Jeremiah Curtin,[43] it was possibly in 1636[44] that Vassili Starkov was sent as envoy to the Altyn Khan. He was given 250 pounds of tea as a gift to the tsar. Starkov at first refused, seeing no use for a load of dead leaves, but the Khan insisted. Thus was tea introduced to Russia. In 1679, Russia concluded a treaty on regular tea supplies from China via camel caravan in exchange for furs. It is today considered the de facto national beverage.

The Raymond, Hugh Mckay Commander. The first vessel direct from China to Hull on her arrival on 14 October 1843 with a cargo of tea.

The first record of tea in English came from a letter written by Richard Wickham, who ran an East India Company office in Japan, writing to a merchant in Macao requesting "the best sort of chaw" in 1615. Peter Mundy, a traveller and merchant who came across tea in Fujian in 1637, wrote, "chaa – only water with a kind of herb boyled in it".[45][46] Tea was sold in a coffee house in London in 1657, Samuel Pepys tasted tea in 1660, and Catherine of Braganza took the tea-drinking habit to the English court when she married Charles II in 1662. Tea, however, was not widely consumed in the British Isles until the 18th century and remained expensive until the latter part of that period. English drinkers preferred to add sugar and milk to black tea, and black tea overtook green tea in popularity in the 1720s.[47] Tea smuggling during the 18th century led to the general public being able to afford and consume tea. The British government removed the tax on tea, thereby eliminating the smuggling trade, by 1785.[48] In Britain and Ireland, tea was initially consumed as a luxury item on special occasions, such as religious festivals, wakes, and domestic work gatherings. The price of tea in Europe fell steadily during the 19th century, especially after Indian tea began to arrive in large quantities; by the late 19th century tea had become an everyday beverage for all levels of society.[49] The popularity of tea played a role in historical events – the Tea Act of 1773 provoked the Boston Tea Party that escalated into the American Revolution. The need to address the issue of British trade deficit because of the trade in tea resulted in the Opium Wars. The Qing Kangxi Emperor had banned foreign products from being sold in China, decreeing in 1685 that all goods bought from China must be paid for in silver coin or bullion.[50] Traders from other nations then sought to find another product, in this case opium, to sell to China to earn back the silver they were required to pay for tea and other commodities. The subsequent attempts by the Chinese Government to curtail the trade in opium led to war.[51]

World map of tea exporters and importers, 1907
World map of tea exporters and importers, 1907

Chinese small-leaf-type tea was introduced into India in 1836 by the British in an attempt to break the Chinese monopoly on tea.[52] In 1841, Archibald Campbell brought seeds of Chinese tea from the Kumaun region and experimented with planting tea in Darjeeling. The Alubari tea garden was opened in 1856, and Darjeeling tea began to be produced.[53] In 1848, Robert Fortune was sent by the East India Company on a mission to China to bring the tea plant back to Great Britain. He began his journey in high secrecy as his mission occurred in the lull between the First Opium War and the Second Opium War.[54] The Chinese tea plants he brought back were introduced to the Himalayas, though most did not survive. The British had discovered that a different variety of tea was endemic to Assam and the northeast region of India, which was then hybridized with Chinese small-leaf-type tea. Using Chinese planting and cultivation techniques, the British colonial government established a tea industry by offering land in Assam to any European who agreed to cultivate it for export.[52] Tea was originally consumed only by Anglo-Indians; however, it became widely popular in India in the 1950s because of a successful advertising campaign by the India Tea Board.[52] The British introduced tea industry to Sri Lanka (then Ceylon) in 1867.[55]

Chemical composition

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See also: Phenolic content in tea

Physically speaking, tea has properties of both a solution and a suspension. It is a solution of the water-soluble compounds extracted from the tea leaves, such as the polyphenols and amino acids. Tea infusions are among most consumed beverages globally.[56]

Caffeine makes up about 3% of tea's dry weight, which translates to between 30 and 90 milligrams per 250-millilitre (8+1⁄2 US fl oz) cup depending on the type, brand,[57] and brewing method.[58] A study found that the caffeine content of one gram of black tea ranged from 22 to 28 mg, while the caffeine content of one gram of green tea ranged from 11 to 20 mg, reflecting a significant difference.[59] Tea contains small amounts of theobromine and theophylline, which are xanthines and stimulants, similar to caffeine.[60]

Fresh tea leaves in various stages of growth

The astringency in tea can be attributed to the presence of polyphenols. These are the most abundant compounds in tea leaves, making up 30–40% of their composition.[61] Polyphenols in tea include flavonoids, epigallocatechin gallate (EGCG), and other catechins.[62][63] Although there has been preliminary clinical research on whether green or black teas may protect against various human diseases, there is no evidence that tea polyphenols have any effect on health or lowering disease risk.[64][65]

Health effects

[edit]
Main article: Health effects of tea

Although health benefits have been assumed throughout the history of Camellia sinensis's consumption, there is no high-quality evidence showing that tea consumption gives significant benefits other than possibly increasing alertness, an effect caused by caffeine in the tea leaves.[66][67] In clinical research conducted in the early 21st century, it was found there is no scientific evidence to indicate that consuming tea affects any disease or improves health.[66]

Black and green teas contain no essential nutrients in significant amounts, with the exception of the dietary mineral manganese, at 0.5 mg per cup or 26% of the Reference Daily Intake (RDI).[68] Fluoride is sometimes present in tea; certain types of "brick tea", made from old leaves and stems, have the highest levels, enough to pose a health risk if much tea is drunk, which has been attributed to high levels of fluoride in soils, acidic soils, and long brewing.[69]

Cultivation and harvesting

[edit]

Tea harvesting in Zhejiang province, China, May 1987
Tea plantation workers in Sri Lanka

Camellia sinensis is an evergreen plant that grows mainly in tropical and subtropical climates.[70] Some varieties can tolerate oceanic climates and are cultivated as far north as Cornwall in England,[71] Perthshire in Scotland,[citation needed] Washington in the United States,[72] and Vancouver Island in Canada.[73] In the Southern Hemisphere, tea is grown as far south as Hobart in Tasmania[74][75] and Waikato in New Zealand.[76]

Tea plants are propagated from seed and cuttings; about 4 to 12 years are needed for a plant to bear seed and about three years before a new plant is ready for harvesting.[70] In addition to a zone 8 climate or warmer, tea plants require at least 1,200 millimetres (47 in) of rainfall per year and prefer acidic soils.[77] Many high-quality tea plants are cultivated at elevations of up to 2,000 metres (6,600 ft) above sea level. Though at these heights the plants grow more slowly, they acquire a better flavour.[78]

Tea plantations around Mattupetty lake near Munnar, India

Two principal varieties are used: Camellia sinensis var. sinensis, which is used for most Chinese, Formosan and Japanese teas, and C. sinensis var. assamica, used in Pu-erh and most Indian teas (but not Darjeeling). Within these botanical varieties, many strains and modern clonal varieties are known. Leaf size is the chief criterion for the classification of tea plants, with three primary classifications being:[79] Assam type, characterised by the largest leaves; China type, characterised by the smallest leaves; and Cambodian type, characterised by leaves of intermediate size. The Cambodian-type tea (C. assamica subsp. lasiocaly) was originally considered a type of Assam tea. However, later genetic work showed that it is a hybrid between Chinese small-leaf tea and Assam-type tea.[80] Darjeeling tea appears to be a hybrid between Chinese small-leaf tea and Assam-type large-leaf tea.[21]

Women picking tea in Kenya

A tea plant will grow into a tree of up to 16 m (52 ft) if left undisturbed,[70] but cultivated plants are generally pruned to waist height for ease of plucking. The short plants bear more new shoots which provide new and tender leaves and increase the quality of the tea.[81] Only the top 25 to 50 millimetres (1 to 2 in) of the mature plant are picked. These buds and leaves are called 'flushes'.[82] A plant will grow a new flush every 7 to 15 days during the growing season. Leaves that are slow in development tend to produce better-flavoured teas.[70] Several teas are available from specified flushes; for example, Darjeeling tea is available as first flush (at a premium price), second flush, monsoon and autumn. Assam second flush or "tippy" tea is considered superior to first flush, because of the gold tips that appear on the leaves.

Tea plantation near Sa Pa, Vietnam

Pests that can afflict tea plants include mosquito bugs, genus Helopeltis, which are true bugs and not to be confused with dipterous insects of family Culicidae ('mosquitos'). Mosquito bugs can damage leaves both by sucking plant materials, and by the laying of eggs (oviposition) within the plant. Spraying with synthetic insecticides may be deemed appropriate.[83] Other pests are Lepidopteran leaf feeders and various tea diseases.

Production

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Tea production – 2022
Country Million
tonnes
 China
14.53
 India
5.97
Kenya Kenya
2.33
Sri Lanka Sri Lanka
1.40
 Turkey
1.30
 Vietnam
1.12
 Indonesia
0.60
 Bangladesh
0.44
 Argentina
0.36
 Uganda
0.33
World 29.76
Source: (FAO)[84]

Tea is mainly grown in Asia and Africa, with smaller areas in South America and around the Black and Caspian Seas. The four biggest tea-producing countries are China, India, Kenya and Sri Lanka, together representing 81% of world tea production. Smaller hubs of production include such places as São Miguel Island, Azores, in Portugal, and Guria, in Georgia. In 2022, global production of tea was 29.8 million tonnes, led by China with 49% and India with 20% of the world total. Kenya, Sri Lanka, and Turkey were secondary producers.[85]

Storage

[edit]

Storage conditions determine the shelf life of tea; black tea shelf life is greater than that of green teas. Some, such as flower teas, may last only a month or so. Others, such as pu-erh, improve with age. To remain fresh and prevent mold, tea needs to be stored away from heat, light, air, and moisture. Tea must be kept at room temperature in an air-tight container. Black tea in a bag within a sealed opaque canister may keep for two years. Green tea deteriorates more rapidly, usually in less than a year. Tightly rolled gunpowder tea leaves keep longer than the more open-leafed Chun Mee tea.

Storage life for all teas can be extended by using desiccant or oxygen-absorbing packets, vacuum sealing, or refrigeration in air-tight containers (except green tea, where discrete use of refrigeration or freezing is recommended and temperature variation kept to a minimum).[86]

Processing and classification

[edit]
Main article: Tea processing
Teas of different levels of oxidation (L to R): green, yellow, oolong, and black

Tea is divided into categories based on how it is processed.[87] At least six different types are produced:

  • White: wilted and unoxidized;
  • Yellow: unwilted and unoxidized but allowed to yellow;
  • Green: unwilted and unoxidized;
  • Oolong: wilted, bruised, and partially oxidized;
  • Black: wilted, sometimes crushed, and fully oxidized (called 紅茶 [hóngchá], "red tea" in Chinese and other East Asian tea culture);
  • Post-fermented (Dark): green tea that has been allowed to ferment/compost (called Pu'er if from the Yunnan district of South-Western China or 黑茶 [hēichá] "black tea" in Chinese tea culture).

After picking, the leaves of C. sinensis soon begin to wilt and oxidize unless immediately dried. An enzymatic oxidation process triggered by the plant's intracellular enzymes causes the leaves to turn progressively darker as their chlorophyll breaks down and tannins are released. This darkening is stopped at a predetermined stage by heating, which deactivates the enzymes responsible. In the production of black teas, halting by heating is carried out simultaneously with drying. Without careful moisture and temperature control during manufacture and packaging, growth of undesired molds and bacteria may make tea unfit for consumption.

Blending and additives

[edit]
Further information: Tea blending and additives
Common processing methods of tea leaves

After basic processing, teas may be altered through additional processing steps before being sold[88] and is often consumed with additions to the basic tea leaf and water added during preparation or drinking. Examples of additional processing steps that occur before tea is sold are blending, flavouring, scenting, and decaffeination of teas. Examples of additions added at the point of consumption include milk, sugar and lemon.

Tea blending is the combination of different teas together to achieve the final product. Such teas may combine others from the same cultivation area or several different ones. The aim is to obtain consistency, better taste, higher price, or some combination of the three.

Flavoured and scented teas are enhancements of the base tea. This can be accomplished through directly adding flavouring agents, such as ginger, cloves, mint leaves, cardamom, bergamot (found in Earl Grey), vanilla, and spearmint. Alternatively, because tea easily retains odours, it can be placed in proximity to an aromatic ingredient to absorb its aroma, as in traditional jasmine tea.[89]

Black tea is often taken with milk.

The addition of milk to tea in Europe was first mentioned in 1680 by the epistolist Madame de Sévigné.[90] Many teas are traditionally drunk with milk in cultures where dairy products are consumed. These include Indian masala chai and British tea blends. These teas tend to be very hearty varieties of black tea which can be tasted through the milk, such as Assams, or the East Friesian blend. Milk is thought to neutralise remaining tannins and reduce acidity.[91][92] The Han Chinese do not usually drink milk with tea but the Manchus do, and the elite of the Qing Dynasty of the Chinese Empire continued to do so. Hong Kong-style milk tea is based on British habits. Tibetans and other Himalayan peoples traditionally drink tea with milk or yak butter and salt. In Eastern European countries, and in Russia and Italy, tea is commonly served with lemon juice. In Poland, tea is traditionally served with a slice of lemon and is sweetened with either sugar or honey; tea with milk is called a bawarka ("Bavarian style") in Polish and is widely popular.[93] In Australia, tea with milk is known as "white tea".

The order of steps in preparing a cup of tea is a much-debated topic and can vary widely between cultures and individuals. Some say it is preferable to add the milk to the cup before the tea, as the high temperature of freshly brewed tea can denature the proteins found in fresh milk, similar to the change in taste of UHT milk, resulting in an inferior-tasting beverage.[94] Others insist it is better to add the milk to the cup after the tea, as black tea is often brewed as close to boiling as possible. The addition of milk chills the beverage during the crucial brewing phase, if brewing in a cup rather than using a pot, meaning the delicate flavour of a good tea cannot be fully appreciated. By adding the milk afterwards, it is easier to dissolve sugar in the tea and to ensure the desired amount of milk is added, as the colour of the tea can be observed.[95] Historically, the order of steps was taken as an indication of class: only those wealthy enough to afford good-quality porcelain would be confident of its being able to cope with being exposed to boiling water unadulterated with milk.[96] Higher temperature difference means faster heat transfer, so the earlier milk is added, the slower the drink cools. A 2007 study published in the European Heart Journal found certain beneficial effects of tea may be lost through the addition of milk.[97]

Packaging

[edit]

Tea bags

[edit]
Main article: Tea bag
Tea bags

In 1907, American tea merchant Thomas Sullivan began distributing samples of his tea in small bags of silk with a drawstring. Consumers noticed they could simply leave the tea in the bag and reuse it with fresh tea. However, the potential of this distribution and packaging method would not be fully realised until later. During World War II, tea was rationed in the United Kingdom. In 1953, after rationing in the UK ended, Yorkshire-based tea manufacturer Tetley launched the tea bag in the UK, and it was an immediate success.

The "pyramid tea bag" (or sachet), introduced by Lipton[98] and PG Tips/Scottish Blend in 1996,[99] attempts to address one of the connoisseurs' arguments against paper tea bags by way of its three-dimensional tetrahedron shape, which allows more room for tea leaves to expand while steeping.[100] However, some types of pyramid tea bags have been criticised as being environmentally unfriendly, since their synthetic material is not as biodegradable as loose tea leaves and paper tea bags.[101]

Loose tea

[edit]
A blend of loose-leaf black teas

The tea leaves are packaged loosely in a canister, paper bag, or other container such as a tea chest. Some whole teas, such as rolled gunpowder tea leaves, which resist crumbling, are vacuum-packed for freshness in aluminised packaging for storage and retail. The loose tea is individually measured for use, allowing for flexibility and flavour control at the expense of convenience. Strainers, tea balls, tea presses, filtered teapots, and infusion bags prevent loose leaves from floating in the tea and over-brewing. A traditional method uses a three-piece lidded teacup called a gaiwan, the lid of which is tilted to decant the tea into a different cup for consumption.

Compressed tea

[edit]
Sheng (raw) pu-erh tuo cha, a type of compressed aged raw pu-erh

Tea bricks or compressed tea are produced for convenience in transport, storage, and ageing. It can usually be stored longer without spoilage than loose leaf tea. Compressed tea is prepared by loosening leaves from the cake using a small knife, and steeping the extracted pieces in water. During the Tang dynasty, as described by Lu Yu, compressed tea was ground into a powder, combined with hot water, and ladled into bowls, resulting in a "frothy" mixture.[102] In the Song dynasty, the tea powder would instead be whisked with hot water in the bowl. Although no longer practiced in China today, the whisking method of preparing powdered tea was transmitted to Japan by Zen Buddhist monks, and is still used to prepare matcha in the Japanese tea ceremony.[103] Chinese pu-erh is often distributed in the form, as other teas may sometimes be.

Compressed tea was the most popular form of tea in China during the Tang dynasty.[104] By the beginning of the Ming dynasty, it had been displaced by loose-leaf tea.[105] It remains popular, however, in the Himalayan countries and Mongolian steppes. In Mongolia, tea bricks were ubiquitous enough to be used as a form of currency. Among Himalayan peoples, compressed tea is consumed by combining it with yak butter and salt to produce butter tea.[106]

Instant tea

[edit]
Main article: Instant tea

"Instant tea", similar to freeze-dried instant coffee and an alternative to brewed tea, can be consumed either hot or cold. Instant tea was developed in the 1930s, with Nestlé introducing the first commercial product in 1946, while Redi-Tea debuted instant iced tea in 1953. Additives such as chai, vanilla, honey or fruit, are popular, as is powdered milk.

During the Second World War British and Canadian soldiers were issued an instant tea in their composite ration ("compo") packs. These blocks of instant tea, powdered milk, and sugar were not always well received. As Royal Canadian Artillery Gunner, George C Blackburn observed:

But, unquestionably, the feature of Compo rations destined to be remembered beyond all others is Compo tea...Directions say to "sprinkle powder on heated water and bring to the boil, stirring well, three heaped teaspoons to one pint of water." Every possible variation in the preparation of this tea was tried, but...it always ended up the same way. While still too hot to drink, it is a good-looking cup of strong tea. Even when it becomes just cool enough to be sipped gingerly, it is still a good-tasting cup of tea, if you like your tea strong and sweet. But let it cool enough to be quaffed and enjoyed, and your lips will be coated with a sticky scum that forms across the surface, which if left undisturbed will become a leathery membrane that can be wound around your finger and flipped away...[107]

Bottled and canned tea

[edit]
Main article: Canned tea

Canned tea is sold prepared and ready to drink. It was introduced in 1981 in Japan. The first bottled tea was introduced by an Indonesian tea company, PT. Sinar Sosro in 1969 with the brand name Teh Botol Sosro (or Sosro bottled tea).[108] In 1983, Swiss-based Bischofszell Food Ltd. was the first company to bottle iced tea on an industrial scale.[109]

Tea culture

[edit]
Main article: Tea culture
See also: American tea culture, Argentine tea culture, Azerbaijani tea culture, Brazilian tea culture, Dominican tea culture, Indian tea culture, Tea culture in Japan, Mexican tea culture, Russian tea culture, and Senegalese tea culture

In many cultures, tea is consumed at elevated social events, such as the tea party. Tea ceremonies have arisen in different cultures, such as the Chinese and Japanese traditions, each of which employs certain techniques and ritualised protocol of brewing and serving tea for enjoyment in a refined setting. One form of Chinese tea ceremony is the Gongfu tea ceremony, which typically uses small Yixing clay teapots and oolong tea.

In the United Kingdom, 63% of people drink tea daily.[110] It is customary for a host to offer tea to guests soon after their arrival. Tea is consumed both at home and outside the home, often in cafés or tea rooms. Afternoon tea with cakes on fine porcelain is a cultural stereotype. In southwest England, many cafés serve a cream tea, consisting of scones, clotted cream, and jam alongside a pot of tea.

Tea being served in Karbala, Iraq

Ireland, as of 2016, was the second-biggest per capita consumer of tea in the world, after Turkey.[111] Local blends are the most popular in Ireland, including Irish breakfast tea, using Rwandan, Kenyan and Assam teas. The annual national average of tea consumption in Ireland is 2.7 kg to 4 kg per person. Tea in Ireland is usually taken with milk or sugar and brewed longer for a stronger taste.[112]

Turkish tea is an important part of that country's cuisine and is the most commonly consumed hot drink, despite the country's long history with coffee. In 2004, Turkey produced 205,500 tonnes of tea (6.4% of the global total), which made it one of the largest tea markets in the world,[113] with 120,000 tons being consumed in Turkey and the rest being exported.[114] In 2010, Turkey had the highest per capita consumption in the world at 2.7 kg.[115] As of 2013, the per-capita consumption of Turkish tea exceeds 10 cups per day and 13.8 kg per year.[116] Tea is grown mostly in Rize Province on the Black Sea coast.[117]

South Indian woman preparing a cup of morning tea in the traditional South Indian way

Russia has a long, rich tea history dating to 1638 when tea was introduced to Tsar Michael. Social gatherings were considered incomplete without tea, which was traditionally brewed in a samovar.[118]

In Pakistan, both black and green teas are popular and are known locally as sabz chai and kahwah, respectively. The popular green tea is often served after every meal in the Pashtun belt of Balochistan and in Khyber Pakhtunkhwa. In central and southern Punjab and the metropolitan Sindh region of Pakistan, tea with milk and sugar (sometimes with pistachios, cardamom, etc.), commonly referred to as chai, is widely consumed. It is the most common beverage of households in the region. In the northern Pakistani regions of Chitral and Gilgit-Baltistan, a salty, buttered Tibetan-style tea is consumed.

Indian tea culture is strong; the drink is the most popular hot beverage in the country. It is consumed daily[119] in almost all houses, offered to guests, consumed in high amounts in domestic and official surroundings, and is made with the addition of milk with or without spices, and usually sweetened. It is sometimes served with biscuits to be dipped in the tea and eaten before consuming the tea. More often than not, it is drunk in "doses" of small cups (referred to as "cutting" chai if sold at street tea vendors) rather than one large cup.

tea in narrow waist glass
Iranians usually drink tea with rock candy or ghand and in glass cups.

Iranians have one of the highest per capita rates of tea consumption in the world. Châikhânes (teahouses) are common in Iran.[120] Iranian tea is typically served in traditional Iranian glasses with a traditional saucer and teaspoon. Tea is cultivated in northern Iran along the shores of the Caspian Sea.[121]

In Burma (Myanmar), tea is consumed not only as hot drinks, but also as sweet tea and green tea known locally as laphet-yay and laphet-yay-gyan, respectively. Pickled tea leaves, known locally as lahpet, are a national delicacy. Pickled tea is usually eaten with roasted sesame seeds, crispy fried beans, roasted peanuts and fried garlic chips.[122]

In Mali, gunpowder tea is served in series of three, starting with the highest oxidisation or strongest, unsweetened tea, locally referred to as "strong like death", followed by a second serving, where the same tea leaves are boiled again with some sugar added ("pleasant as life"), and a third one, where the same tea leaves are boiled for the third time with yet more sugar added ("sweet as love"). Green tea is the central ingredient of a distinctly Malian custom, the "Grin", an informal social gathering that cuts across social and economic lines, starting in front of family compound gates in the afternoons and extending late into the night, and is widely popular in Bamako and other large urban areas.[123]

In the United States, 80% of tea is consumed as iced tea.[124] Sweet tea is native to the southeastern U.S. and is iconic in its cuisine due to its refreshing temperature and large amount of sweetener.[125]

Economics

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Producers and consumers

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Further information: List of countries by tea consumption per capita
Tea factory in Taiwan

Tea is the most popular manufactured drink consumed in the world, equaling all others – including coffee, soft drinks, and alcohol – combined.[10] Most tea consumed outside East Asia is produced on large plantations in the hilly regions of India and Sri Lanka and is destined to be sold to large businesses. Opposite this large-scale industrial production are many small "gardens," sometimes minuscule plantations, that produce highly sought-after teas prized by gourmets. These teas are both rare and expensive and can be compared to some of the most expensive wines in this respect.[citation needed]

India is the world's largest tea-drinking nation,[126] although the per capita consumption of tea remains a modest 750 grams (26 oz) per person every year. Turkey, with 2.5 kilograms (5 lb 8 oz) of tea consumed per person per year, is the world's greatest per capita consumer.[127]

Certification

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Several bodies independently certify the production of tea, such as Rainforest Alliance, Fairtrade, UTZ Certified, and Organic. From 2008 to 2016, sustainability standards-certified tea production experienced a compound annual growth rate of about 35%, accounting for at least 19% of overall tea production. In 2016, at least 1.15 million tonnes of sustainably certified tea was produced, valued at US$2 billion.[128]

Rainforest Alliance certified tea is sold by Unilever brands Lipton and PG Tips in Western Europe, Australia and the U.S. Fairtrade certified tea is sold by a large number of suppliers around the world. UTZ Certified tea is sold by Pickwick tea.[129]

Issues

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Safety

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Tests of commercially popular teas have detected residues of banned toxic pesticides.[130][131]

Fraud

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Tea is a common target of food fraud. Lower cost ingredients may be substituted for tea, or a tea may be adulterated with undeclared and possibly toxic colors and flavors. The origin of the tea, picking season, and the processing techniques may be intentionally misidentified. Tea powders which undergo additional processing are more susceptible to food fraud.[132]

Labour

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Tea production in Kenya, Malawi, Rwanda, Tanzania, and Uganda uses child labour, according to the U.S. Department of Labor's List of Goods Produced by Child Labor or Forced Labor.[133] Workers who pick and pack tea on plantations in developing countries can face harsh working conditions and may earn below the living wage.[134]

See also

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Other drinks

References

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[edit]
Revisions and contributorsEdit on WikipediaRead on Wikipedia

Tea

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from Grokipedia
Tea is an aromatic beverage prepared by infusing the cured or fresh leaves of , an evergreen shrub native to , in hot water, resulting in one of the world's most widely consumed drinks after water. The plant's leaves and buds undergo varying degrees of oxidation and processing to produce distinct types, including , which is minimally oxidized to preserve fresh, vegetal flavors; , fully oxidized for robust, malty notes; and , partially oxidized to yield complex profiles bridging the two. Originating in , where archaeological evidence and ancient texts trace its use to at least the 3rd century AD, though legend attributes discovery to the emperor around 2737 BCE during herbal experimentation, tea spread globally via trade routes, profoundly influencing cultures, economies, and daily rituals from British afternoon tea to Japanese chanoyu ceremonies. Today, dominates production, accounting for over 50% of global output in recent years, followed by , , and , with the industry supporting millions in cultivation and processing amid challenges like climate variability and labor demands. Empirical studies highlight tea's bioactive compounds, such as catechins and , linked to potential health benefits including effects and cognitive support, though causal claims require cautious interpretation beyond correlative data.

Etymology

Linguistic origins and evolution

The Chinese character 茶 (tèa), denoting the beverage derived from , emerged during the around 760 AD, evolving from earlier terms such as 茗 (míng) or 荼 (tú) used in classical texts like the Shijing (compiled circa 600–1000 BC) to refer to bitter herbal infusions, though not specifically tea as processed leaves. This character standardized the term across Chinese dialects, but regional pronunciations diverged: Mandarin and northern dialects favored chá, while Nan (Hokkien/Fujianese) dialects rendered it as tê or te. These variants propagated globally via trade routes, creating two primary linguistic lineages. The chá form spread overland along the from northern , influencing Persian chây by the 9th century, thence to chai, shāy, chai, and chá (adopted circa 1550s via contacts in ). In contrast, the tê pronunciation traveled maritime routes from ports, entering European lexicon through Dutch traders via the in Amoy (); Dutch thee appeared by the early 1600s, borrowed into English as tea (initially spelled tay or tee) around 1650–1659. Languages adopting the "te" form, such as English tea, French thé, and Spanish té, cluster in northwest and reflect sea-borne commerce, while "cha" derivatives dominate inland , the , and . In English, tea initially rhymed with "obey" or "pay" (/teɪ/), as in mid-17th-century texts, but shifted to /tiː/ by the mid-18th century, coinciding with widespread domestic consumption post-1660s imports. Variant forms like char (from "cha" via Romani or sailor jargon, attested by 1700s) emerged from cross-pollination, but tea standardized by the amid imperial trade. This binary evolution underscores causal trade geography: overland routes preserved the sibilant ch-, while oceanic paths softened to t-.

Regional and trade-influenced terms

The word for tea in most languages derives from one of two Chinese pronunciations: tê from the (Minnan) dialect spoken in province, or chá from northern Mandarin dialects. These variants reflect the paths of tea's dissemination through trade: the tê form predominated along maritime routes from southern Chinese ports, while chá spread via overland caravan paths like the . Maritime trade, beginning in the 16th century with and Dutch merchants, carried the tê pronunciation westward. Dutch traders, sourcing tea from (Amoy) in around 1610, adopted thee from Hokkien tê, which evolved into English "tea" by the 1650s via imports to . This form influenced Western European languages, including French thé, German Tee, and Spanish té. In contrast, the chá variant traveled eastward and northward over land, reaching Persia as chay by the 9th century via exchanges, then spreading to shay, chai, and Russian chai. Exceptions arose from localized trade contacts. traders, active in from 1557, borrowed chá from despite sea routes, influencing Iberian and some African variants like Swahili chai. In regions with dual introductions, hybrid or sequential adoptions occurred; for instance, Japanese initially used cha from Mandarin influences but later incorporated tea forms via Western trade in the .
Trade RouteProto-FormExample Languages and Terms
Maritime (Sea, from ports)têEnglish: tea; Dutch: thee; Indonesian: teh
Overland (, northern routes)cháPersian: chay; : chai; Turkish: çay
This bifurcation underscores how commodity trade shaped linguistic diffusion, with sea routes favoring southern dialect forms and land routes preserving northern ones until global commerce homogenized influences in the 19th century.

Botany

Plant taxonomy and description

The tea plant is scientifically classified as (L.) Kuntze, belonging to the genus in the family . Its full taxonomic hierarchy includes Kingdom Plantae, Phylum Tracheophyta, Class Magnoliopsida, Order , Family Theaceae, Genus Camellia, and Species sinensis. This classification reflects its placement among flowering plants with ericoid characteristics, distinct from older systems that grouped it under Order Theales. The species encompasses two primary varieties: C. sinensis var. sinensis, originating from cooler Chinese highlands with smaller, pointed leaves, and C. sinensis var. assamica, from warmer Indian regions featuring larger, broader leaves adapted to tropical lowlands. Camellia sinensis grows as an evergreen shrub or small tree, typically reaching 1 to 5 meters in height when cultivated, though wild specimens can exceed 10 meters if unpruned. The plant exhibits a bushy habit with numerous branches, pruned in cultivation to waist height for efficient leaf harvesting. Leaves are alternate, elliptical to ovate, 4–15 cm long and 2–5 cm wide, leathery, glossy dark green above with a paler underside, and finely serrated margins. Flowers are solitary or clustered, axillary, white, fragrant, and measure 2.5–4 cm in diameter with 5–8 petals and numerous stamens. The fruit is a woody, dehiscent capsule, approximately 2–3 cm in diameter, three-lobed, each lobe containing 1–3 spherical seeds about 1 cm across, enclosed by persistent sepals. Var. sinensis tends toward more compact growth suitable for higher elevations, while var. assamica develops into taller, tree-like forms with bolder foliage in lowland tropics. These morphological differences influence processing yields and flavor profiles, with assamica leaves yielding robust infusions due to higher theanine and caffeine content under warmer conditions.

Varieties, cultivars, and genetic hybrids

The tea plant, , encompasses two primary botanical varieties: C. sinensis var. sinensis (Chinese type) and C. sinensis var. assamica (Assam type), distinguished by morphological, physiological, and genetic traits adapted to their native environments. Var. sinensis, originating from subtropical regions of , features smaller, narrower leaves (typically 4–7 cm long), a more compact bush form, and greater tolerance to cooler temperatures and higher elevations (up to 2,000 meters), enabling cultivation in diverse climates from to . In contrast, var. assamica, native to the tropical region of , exhibits larger, broader leaves (8–20 cm long), a taller, less branched growth habit, and preference for lowland, warmer conditions (below 1,000 meters) with higher rainfall, yielding bolder, more robust teas suited to production in regions like and . Genetic analyses confirm these varieties diverged through and adaptation, with var. assamica showing higher heterozygosity and adaptation to heat stress via distinct frequencies in stress-response genes.
VarietyLeaf Size and ShapeClimate PreferenceTypical Uses and Traits
C. s. var. sinensisSmall, narrow (4–7 cm)Cooler, higher elevations (subtropical to temperate)Fine, nuanced flavors; / teas; cold-hardy
C. s. var. assamicaLarge, broad (8–20 cm)Warm, lowland tropicsBold, ; teas; high yield in heat
Cultivars represent within these varieties, yielding thousands of named strains optimized for yield, flavor profiles, pest resistance, and processing suitability; China alone maintains over 2,000 registered cultivars, primarily from var. sinensis, such as 'Fuding Dabai' for or 'Longjing 43' for , selected via clonal for uniform quality and content. In and , assamica-derived cultivars like 'Tocklai' clones emphasize vegetative vigor and drought tolerance, with assessed via markers like AFLP showing clustering by origin and hybrid . These cultivars arise from empirical selection rather than formal hybridization programs until the , preserving local adaptations while enhancing commercial traits like yield in black teas. Genetic hybrids, often crosses between var. sinensis and var. assamica, aim to combine the finesse of Chinese types with the productivity of types, producing elite progenies with improved biosynthesis and yield; for instance, Chinese Assam hybrids exhibit admixture from multiple tea types, evidenced by data showing from wild relatives. Interspecific hybrids with other species (e.g., C. taliensis) occur naturally due to weak reproductive barriers but are less common in commercial tea, as they often yield inferior beverage quality; breeding programs, such as those in and since the 1950s, have generated F1 hybrids evaluated for traits like metabolism via allele-specific expression analysis. Such hybrids demonstrate in growth but require genomic screening to avoid dilution of flavor compounds, with studies confirming parental bias in influencing hybrid vigor.

History

Ancient origins and domestication

The tea plant, , originated in the subtropical forests of southwest , with its wild progenitor centered in province and adjacent regions extending into northern and Indochina. Genetic studies of and nuclear DNA from wild and cultivated populations confirm this area as the primary center of diversity and , where ancient forest trees grew to heights exceeding 15 meters before human intervention. Domestication began through selective harvesting and propagation of wild varieties, favoring smaller-leaved C. sinensis var. sinensis over the larger-leaved var. assamica, to produce shrubs amenable to repeated plucking and processing into a beverage. This process, estimated to have started over 3,000 years ago based on linguistic and archaeobotanical correlations, transformed tea from a sporadically foraged medicinal into a cultivated crop. Initial uses likely involved chewing leaves or boiling them as a bitter tonic, with evidence of systematic cultivation emerging by the (c. 1046–256 BC). The earliest verifiable physical evidence of tea consumption dates to the (206 BC–220 AD), where chemical residues of and —hallmarks of C. sinensis—were identified in funerary artifacts from a in dated to 141 BC, indicating elite use as a beverage or offering. Further analysis of Han-era sites reveals tea's presence along early trade routes into the by around 1800 years BP (c. 200 AD), predating widespread textual documentation. These findings align with genetic bottlenecks in domesticated lineages, signaling human-driven selection pressures dating back millennia, though direct pre-Han archaeological confirmation remains elusive. Chinese legend attributes tea's discovery to the divine farmer in 2737 BC, who purportedly observed leaves imparting medicinal properties to boiling water, but this narrative first appears in Tang-era texts like Lu Yu's The Classic of Tea (c. 760 AD) and lacks corroboration from contemporary records or artifacts, functioning more as etiological myth than historical account. Empirical domestication timelines, inferred from pollen records and varietal divergence, suggest gradual intensification from foraging practices in the Yangtze River basin onward, with full agrarian integration by the .

Spread within Asia

Tea cultivation, domesticated in southwestern China by the 3rd century BCE, disseminated to neighboring regions primarily through Buddhist monastic networks and imperial trade routes. By the CE, tea seeds and consumption practices reached the Korean Peninsula during the period, with documented imports from China facilitating early cultivation in mountainous areas like Jiri Mountain. This introduction aligned with the reign of Queen Seondeok (632–647 CE), when (nokcha) was adopted for medicinal and ritual purposes among elites and monks, though widespread farming remained limited until later dynasties. In Japan, tea arrived via Chinese Buddhist envoys in the early , initially as a medicinal tonic for monks during . and , returning from Tang around 805–815 CE, are credited with smuggling seeds that enabled the first plantings at temples in and . The practice gained traction under (1141–1215 CE), whose treatise Kissa Yōjōki (1191 CE) advocated tea for health and Zen discipline, spurring cultivation in by the and evolving into the formalized tea ceremony (chanoyu) by the 16th century. Vietnam's tea heritage traces to indigenous wild Camellia sinensis varieties in the northern highlands, with cultivation evidence from the 13th–15th centuries influenced by Chinese migration and proximity to Province. Ancient trees exceeding 1,000 years old persist in regions like Thai Nguyen, supporting green and lotus-scented teas integral to daily rituals and ancestor veneration. Parallel to this, wild tea shrubs native to India's and regions were harvested by indigenous groups like the Singpho for decoctions predating organized farming, though systematic Chinese-style processing arrived later via overland routes. By the , Fujianese migrants transplanted and high-mountain varieties to , establishing it as a major producer by 1868 with cultivars like Alishan. These transmissions underscore tea's role in fostering shared cultural institutions across East and , distinct from subsequent European-mediated expansions.

Global trade and colonial expansion

Tea reached in the early 16th century through traders who established contact with southern in 1514, becoming the first Europeans to import and consume the beverage, primarily as a medicinal tonic. merchants followed, delivering the first commercial shipments from in 1610 via the , initially distributing tea among elites in the and later across . The British East India Company, chartered in 1600, entered the tea trade more substantially by the late 17th century, with tea imports to Britain surging from negligible amounts in 1660 to over 5 million pounds annually by 1750, fueled by declining prices and growing domestic demand. High British import duties, peaking at 119% in the , spurred widespread , with illegal imports exceeding legal ones by the 1780s—approximately 3,000 tonnes smuggled versus 2,000 tonnes official—undermining the Company's monopoly and prompting repeated legislative adjustments like the Commutation Act of 1784, which halved duties to curb evasion. To address the trade imbalance—Britain exported little desired beyond silver—the Company increasingly shipped Indian-grown to from the 1770s, exchanging it for tea; by 1830, comprised 40% of 's imports from Britain, reversing the silver flow but addicting millions and provoking crackdowns. This escalated into the (1839–1842), where British naval superiority forced the , ceding , opening five , and legalizing , while the (1856–1860) further dismantled Chinese trade restrictions, enabling freer tea exports but at the cost of territorial concessions and indemnities exceeding 20 million silver dollars. To circumvent China's production monopoly and reduce dependency, the British initiated tea cultivation in colonial territories; wild tea plants were identified in , , in 1823, leading to experimental plantations under auspices from 1835, with commercial exports commencing by 1840 and output reaching 10,000 chests (about 500 tonnes) annually by 1860 through coerced labor systems. In Ceylon (modern ), British planters shifted from after a 1869 epidemic, importing seeds in 1839 and establishing the first viable estate at Loolecondera in 1867 under James , whose methods scaled production to over 10 million pounds by 1890, reliant on imported Tamil laborers from under indentured contracts often amounting to . These imperial ventures transformed tea from a Chinese near-monopoly into a global , with colonial plantations supplying 80% of British imports by 1900, embedding the crop in empires' economic architectures while displacing local ecosystems and enforcing plantation economies across .

Industrialization and modern breeding

The industrialization of tea production accelerated in the mid-19th century as European powers, particularly Britain, sought to replicate Chinese cultivation on a commercial scale to reduce dependency on imports. In , native Camellia sinensis var. assamica plants were identified in in 1823, leading to the establishment of the first British-led commercial in , Upper , by 1837. Cultivation expanded to high-altitude regions like , where Archibald Campbell initiated planting with Chinese (sinensis) seeds in 1841, culminating in the Tukvar Tea Estate as the first commercial operation in 1850. This shift to monoculture enabled , with steam-powered machinery introduced for withering, rolling, and drying processes, transforming artisanal methods into factory-based production. In Ceylon (present-day ), the collapse of coffee plantations due to rust disease in the 1870s prompted a rapid transition to ; planted the inaugural estate at Loolecondera in 1867, with the first mechanized factory operational by 1872. Key innovations included the drier in 1877 for efficient moisture removal and rolling machines in 1880 for consistent leaf breakdown, boosting output to over 400,000 acres by 1899. Steamships further industrialized by slashing transit times from or to —reaching 45 days to by 1871—facilitating standardized as a mass commodity. By the early , production spread to African colonies like , where large estates adopted similar mechanized processing, yielding annual global outputs exceeding 100,000 metric tons in major producers by the 1920s. Modern tea breeding built on millennia of selection in , where natural and artificial hybridization produced diverse cultivars over 1,000 years, but systematic programs intensified in the to prioritize yield, disease resistance, and flavor consistency. Clonal propagation via cuttings, pioneered in during the 1920s and refined globally by the , allowed vegetative replication of elite bushes, ensuring uniform traits like high content or pest tolerance across plantations. Hybridization between sinensis and assamica varieties, alongside wild relatives like , generated vigorous F1 and backcross lines for adaptability, with over 5,100 accessions conserved in and for . Contemporary efforts incorporate genomic selection and marker-assisted breeding to accelerate gains, targeting traits such as elevated for in Chinese albino teas or drought resistance via epigenetic modifications like . In , programs emphasize Himalayan for quality enhancement, while global cultivation now spans 5 million hectares, supporting cultivars resilient to biotic stresses through multi-omics analysis.

Cultivation and Harvesting

Environmental requirements

Tea plants (Camellia sinensis) thrive in tropical and subtropical climates with temperatures ranging from 13°C to 30°C, though optimal growth occurs between 18°C and 25°C. Frost can damage young shoots, while temperatures above 30°C may inhibit growth and reduce yield. Annual rainfall of at least 1,200 mm is required, with 1,500–3,000 mm considered ideal for even distribution throughout the year to maintain without waterlogging. High relative of 75–85% supports vigorous growth, while excessive direct (over 40% sunshine hours) can scorch leaves; partial shade or cloudy conditions are preferred. Soils must be deep, well-drained, and acidic with a of 4.5–5.5 to facilitate uptake, particularly iron and aluminum, which are essential for the . or lateritic soils rich in are suitable, but heavy clay or alkaline soils ( above 6.0) hinder root development and cause deficiencies. Tea cultivation succeeds from to altitudes of 2,500 m, with higher elevations (above 1,200 m) yielding slower-growing leaves of superior quality due to cooler temperatures and diurnal fluctuations that enhance flavor compounds. Lowland varieties (C. sinensis var. assamica) favor warmer conditions below 600 m, while highland types (C. sinensis var. sinensis) perform best in cooler, mist-shrouded uplands. Sloping terrain aids drainage and prevents stagnation, common in major producing regions like and .

Propagation, planting, and maintenance

Tea (Camellia sinensis) is predominantly propagated vegetatively through stem cuttings to maintain clonal uniformity of elite cultivars, as seed propagation introduces genetic variability unsuitable for commercial consistency. Semi-hardwood cuttings, typically 10-15 cm long with 2-3 nodes and the top 1-2 leaves retained (often halved to minimize transpiration), are harvested from healthy mother plants in late summer or early autumn. The basal end is treated with a rooting hormone such as indole-3-butyric acid (IBA) at 8000 ppm in talc form, then inserted into a sterile, well-draining medium like perlite-peat mix or sand under mist propagation systems to achieve 70-90% rooting success within 8-12 weeks at 20-25°C. Seed propagation, involving stratified seeds sown in nurseries, is reserved for breeding programs or initial population development, germinating in 4-6 weeks but requiring 2-3 years to reach transplantable size. Rooted cuttings or seedlings are nurtured in shaded nursery beds for 12-18 months until reaching 30-40 cm in height, after which they are hardened off and transplanted to permanent fields during the rainy season to minimize transplant shock. Planting varies by and but typically follows square or rectangular patterns with 1-1.2 m between and 1.5-2 m between rows, accommodating 8,000-10,000 bushes per to optimize light interception and yield. Site preparation includes to 30-45 cm, incorporation of for , and liming if necessary to achieve 4.5-5.5 in well-drained, loamy soils with high organic content. Mulching with leaves or post-planting conserves moisture and suppresses weeds, while initial shading with temporary covers protects against in the first 6-12 months. Ongoing maintenance emphasizes to sustain a compact, productive bush architecture, with young "plumped" or lightly headed back to 30-45 cm three times annually in the first three years (e.g., , , in temperate zones) to encourage lateral branching and prevent legginess. Mature bushes undergo annual hard to 60-90 cm in late winter or post-harvest, removing 20-30% of frame wood to stimulate flushing of tender shoots for plucking. Fertilization follows a balanced NPK regimen (e.g., 200-300 kg N/ha/year split into 3-4 applications), with elevated post- to fuel regrowth, supplemented by micronutrients like and in deficient s; over-fertilization risks leaching and reduced quality. maintains consistent moisture without waterlogging, often via drip systems in dry regions, while targets mites and caterpillars through cultural practices and targeted biopesticides rather than broad-spectrum chemicals. Regular weeding and sustain yields, with bushes remaining productive for 30-50 years under vigilant care.

Harvesting methods and yield factors

Tea harvesting primarily employs two methods: manual plucking and mechanical harvesting. Manual plucking, the traditional approach, involves workers selectively picking the uppermost two leaves and an unopened bud (known as "two leaves and a bud") from Camellia sinensis bushes, which preserves leaf integrity and supports premium tea quality but is labor-intensive, often requiring days for large areas. Mechanical harvesting, conversely, utilizes motorized shears or harvesters to uniformly clip the top 5-10 cm of growth, accelerating the process to hours per hectare while incorporating stems, mature leaves, and occasional damage, which suits bulk production for lower-grade teas. Approximately 70% of global tea bushes now undergo mechanical or mechanically aided harvesting, reflecting efficiency gains amid labor shortages. Harvesting frequency, typically 15-30 days between flushes depending on and variety, directly impacts yield by promoting regeneration; overly frequent plucking exhausts reserves, reducing long-term output, while optimal intervals maximize shoot production. , integrated into the harvesting cycle every 3-5 years, removes leggy growth to stimulate denser foliage and higher yields, though severe initially lowers output by 20-50% before recovery in subsequent seasons, with studies showing net increases of up to 30% in made tea over unpruned after balanced cycles. Plucking standards also modulate yield: fine-plucking for teas yields less per (e.g., 3,000-4,000 kg fresh leaves/ha annually in via hand methods) compared to coarser mechanical cuts, which can double green leaf volumes but diminish processed tea value. Yield per hectare varies regionally and by method, influenced by clonal varieties, altitude, and soil fertility; global averages hover at 1,085 lbs (492 kg) of made tea per acre (about 1,200 kg/ha), with Kenya achieving peaks exceeding 2,500 kg/ha through intensive mechanical harvesting and fertilization, while hand-plucked high-elevation Indian Darjeeling estates yield 400-800 kg/ha due to selective practices prioritizing quality over quantity. Age of bushes negatively correlates with yield, dropping 20-60% after 30-40 years without rejuvenation pruning, underscoring the need for cyclical management to sustain productivity.![Tea harvest in Sri Lanka](./assets/SriLanka_TeaHarvest_(pixinn.net)

Processing

Initial steps: withering and rolling

Withering constitutes the primary post-harvest step in the processing of oxidized teas, including and varieties, wherein freshly plucked leaves are subjected to controlled dehydration. This process typically reduces the content of the leaves from approximately 75-80% to 50-60%, rendering them flaccid and pliable to facilitate mechanical manipulation in later stages. By opening cellular membranes and increasing permeability, withering softens the leaf structure while allowing the dissipation of initial grassy volatiles and the nascent development of flavor and aroma precursors through enzymatic activity. In practice, withering occurs via methods such as trough with forced hot or cool air, or natural outdoor spreading, with duration varying from 6 to 18 hours based on ambient , , and leaf type to achieve uniform loss without initiating uncontrolled oxidation. Following withering, rolling mechanically disrupts the integrity of cells to release containing polyphenols, enzymes, and other intracellular compounds essential for subsequent oxidation. In orthodox , withered leaves are twisted and compressed by hand or via cylindrical rollers, rupturing approximately 60-70% of cell walls and distributing juices evenly across the leaf surface to promote uniform enzymatic reactions. This step not only initiates oxidation by commingling oxidative enzymes like with substrates but also imparts the characteristic twisted shape to whole-leaf grades, influencing final strength and flavor profile. For CTC () methods used in many commercial teas, leaves pass through toothed cylinders that more aggressively shear cells, producing smaller particles suited for quicker but potentially diminishing nuanced flavors compared to orthodox rolling. Rolling duration and pressure are calibrated to avoid over-fragmentation, typically lasting 30-60 minutes in multiple passes, ensuring the released catechins and theaflavins form the basis for the tea's briskness and color upon .

Oxidation, fermentation, and drying

In , oxidation is an enzymatic reaction initiated after withering and rolling, where (PPO) catalyzes the oxidation of catechins and other polyphenols in the presence of oxygen, leading to the formation of theaflavins, thearubigins, and flavor compounds responsible for the characteristics of partially or fully oxidized teas like and . This process typically occurs at controlled temperatures of 24–29 °C for 2–4 hours, or shorter durations of 55–110 minutes in some methods, with humidity and airflow managed to influence the extent of browning and aroma development. The degree of oxidation determines tea classification: minimal for teas (prevented by fixation), partial for and , and full for , where up to 90-100% of catechins are converted. The term "" historically applied to this oxidation step in production is a , as it involves no microbial activity or anaerobic breakdown but rather aerobic enzymatic oxidation akin to . True microbial fermentation occurs post-drying in specific teas like pu-erh, where and fungi alter compounds over weeks or years under controlled moisture, distinct from the rapid enzymatic process in orthodox manufacturing. Enzymatic treatment enhancements, such as exogenous PPO addition, can accelerate formation by 20-50% in some processes, improving color and briskness without altering the fundamental oxidative mechanism. Drying follows oxidation to halt enzymatic activity by rapidly reducing leaf moisture content to 2-5%, preventing further reactions and preserving quality through methods like hot-air convection (100-120 °C initial temperature, reducing to 60-80 °C), fluidized bed drying, or traditional pan-firing. In black tea, primary drying in tray or tunnel dryers achieves 4-6% moisture, followed by secondary firing if needed for aroma fixation, with thermal degradation and Maillard reactions during this stage contributing to final taste and color stability. Over-drying risks brittleness and flavor loss, while under-drying promotes mold; optimal conditions yield uniform, shelf-stable leaves with retained volatile compounds.

Classification by processing type

Tea derived from is primarily classified into six categories based on the degree of enzymatic oxidation and subsequent processing interventions, which determine the final flavor, color, and chemical profile. These categories—white, , , , , and teas—reflect controlled variations in withering, rolling to initiate oxidation, halting oxidation via heat, and optional post-fermentation steps. Oxidation involves enzymes reacting with oxygen, transforming catechins into theaflavins and thearubigins, but true microbial applies only to dark teas. White teas undergo minimal oxidation, typically 0-15%, by withering young buds and leaves under controlled conditions followed by gentle drying without rolling or firing. This preserves delicate floral notes and high levels, as seen in varieties like Silver Needle, harvested from specific cultivars in China's province. Green teas are unoxidized (0%), achieved by rapid heat inactivation of enzymes through steaming (e.g., Japanese ) or pan-firing (e.g., Chinese dragonwell) immediately after harvesting, preventing any browning. This method retains vibrant green hues and grassy flavors, with global production exceeding 2.5 million metric tons annually as of 2020. Yellow teas, rare and mostly Chinese, mirror processing but include a "yellowing" or smothering step that allows limited oxidation (under 10%) in a humid, low-oxygen environment, yielding milder, sweeter profiles than greens without full enzymatic activity. Examples include Junshan Yinzhen, where this step mellows astringency. Oolong teas feature , ranging from 15-80%, where leaves are bruised via rolling to oxidize leaf edges selectively, then oxidation is halted by firing; lighter oolongs (10-30%) resemble greens, while darker ones (60-80%) approach black teas in robustness. Taiwanese high-mountain oolongs exemplify this variability, with times dictating aroma complexity. Black teas (known as red teas in ) achieve near-full oxidation (80-100%) through extended exposure after rolling, which ruptures cell walls to maximize activity, resulting in coppery liquors and malty tastes; orthodox methods contrast with CTC (cut-tear-curl) for faster processing in . Dark teas, including pu-erh, undergo post-fermentation via microbial action after an initial green-tea-like kill step, with raw (sheng) types aged naturally and ripe (shou) accelerated by piling and humidification; this microbial process, involving and bacteria, alters metabolites over months to years, producing earthy depths distinct from oxidation-based types. Production centers in yield over 100,000 tons yearly.

Chemical Composition

Primary bioactive compounds

The primary bioactive compounds in tea from Camellia sinensis are polyphenols, which dominate the chemical profile and account for 20-30% of dry leaf weight in minimally processed forms like green tea. These include catechins—flavan-3-ols such as (-)-epigallocatechin gallate (EGCG), (-)-epigallocatechin (EGC), (-)-epicatechin gallate (ECG), and (-)-epicatechin (EC)—with EGCG typically comprising 40-69% of total catechins by weight in green tea leaves. Total catechins range from 15-40% of dry green tea leaf mass, though extraction efficiency into infusions varies with brewing conditions. In oxidized teas like black tea, enzymatic processes convert catechins into theaflavins (3-6% of dry weight) and thearubigins (10-20%), which maintain flavonoid-like structures but alter solubility and bioavailability. Flavonoid content remains comparable between green and black teas on a total basis (e.g., 124 mg gallic acid equivalents per gram for black vs. 165 for green), but speciation shifts from monomeric catechins to polymeric forms during processing. Alkaloids, primarily (1,3,7-trimethylxanthine), constitute 2-5% of dry leaf weight across tea varieties, with present in trace amounts (<0.1%). Caffeine levels show modest variation by cultivar and growth conditions but are extracted at 20-50 mg per 200 ml infusion depending on leaf age and steeping time. The amino acid L-theanine (γ-glutamylethylamide), unique to Camellia sinensis among major beverages, averages 6.26-6.56 mg/g in leaf dry matter for white and green teas, comprising 1-2% of total amino acids. Shading cultivation increases L-theanine by up to 2-fold, as seen in Japanese gyokuro (up to 85 mg per cup equivalent). Processing minimally affects L-theanine retention, yielding 8-24 mg per standard infusion across tea types. Minor bioactives include flavonol glycosides (e.g., quercetin, kaempferol derivatives at 1-2% dry weight) and volatile compounds, but these contribute less to overall bioactivity than the core polyphenols, alkaloids, and L-theanine. Concentrations vary by C. sinensis varietals (e.g., sinensis vs. assamica), climate, and harvest timing, with young shoots richest in catechins and theanine.
Compound ClassKey ExamplesTypical Dry Leaf ConcentrationProcessing Impact
Catechins (green tea dominant)EGCG, EGC, ECG, EC15-40% total; EGCG 10-20%Oxidized to theaflavins/thearubigins in black tea
Theaflavins/Thearubigins (black tea)BF1, thearubigin polymers3-6% / 10-20%Formed via polyphenol oxidase
AlkaloidsCaffeine2-5%Stable across processing
Amino AcidsL-Theanine1-2% (6-7 mg/g avg.)Retained; higher in shaded leaves

Nutrient profiles and variations

Brewed tea from Camellia sinensis leaves provides negligible macronutrients, with approximately 2 kcal per 240 ml cup, consisting primarily of water (over 99%) and trace amounts of protein (less than 0.5 g), carbohydrates (under 0.3 g), and fats (none detectable). Caffeine content typically ranges from 20-50 mg per cup, depending on leaf type, brewing time, and water temperature, while L-theanine, an amino acid contributing to umami flavor, averages 5-20 mg per cup across varieties. Polyphenols dominate the micronutrient profile, comprising 100-300 mg per cup in total phenolic content, primarily as flavonoids that vary by oxidation level during processing. Minerals include manganese (0.2-0.5 mg per cup, meeting 10-22% of daily needs), fluoride (up to 884 mcg per cup in black tea, influenced by water source and steeping), potassium (around 88 mg), and magnesium (7 mg), with trace selenium, zinc, and chromium. Vitamins are minimal, with small quantities of riboflavin (B2, up to 0.06 mg) and traces of thiamine (B1) and niacin (B3), but insufficient for significant dietary contribution. Processing-induced variations alter bioactive profiles substantially, as minimal oxidation in green and white teas preserves catechins, whereas full oxidation in black tea converts them to theaflavins and thearubigins. Green tea infusions exhibit the highest catechin levels (e.g., epigallocatechin gallate at 50-140 mg per cup) and total antioxidant capacity due to heat inactivation of polyphenol oxidase enzymes. Black tea, conversely, contains lower catechins (under 20 mg) but elevated theaflavins (10-60 mg), which form during enzymatic browning and contribute to darker color and astringency. Oolong teas, partially oxidized (10-70%), display intermediate profiles with catechin levels between green and black (30-80 mg) and emerging theaflavins, while white teas, from unopened buds, retain high catechins similar to green but with delicate flavors and potentially higher amino acids due to shading cultivation. Mineral uptake remains consistent across types, tied to soil and plant physiology, though fluoride and manganese concentrations can increase with longer infusion times. These differences stem from biochemical transformations rather than inherent leaf composition, as all derive from the same species.
Tea TypeTotal Polyphenols (mg/cup)Key Catechins (e.g., EGCG mg/cup)Theaflavins (mg/cup)Manganese (mg/cup)
Green150-30050-140<50.2-0.4
Black100-200<2010-600.3-0.5
Oolong120-25030-805-300.2-0.4
White140-28040-120<100.2-0.3
Data averaged from brewed infusions; values approximate and vary by cultivar, harvest, and preparation.

Analytical methods and quality indicators

High-performance liquid chromatography (HPLC) is the primary method for quantifying catechins, caffeine, and other polyphenols in tea, enabling separation and detection of compounds like epigallocatechin gallate (EGCG) and epicatechin (EC) with high sensitivity and accuracy. Liquid chromatography-tandem mass spectrometry (LC-MS/MS) extends this capability for simultaneous analysis of catechins and theaflavins in black tea, offering detection limits as low as 0.1 μg/mL for key flavonoids. Gas chromatography-mass spectrometry (GC-MS) profiles volatile compounds responsible for tea aroma, identifying over 300 volatiles in black and green teas, with linalool oxides and geraniol serving as markers for quality variations across processing types. Colorimetric assays, such as the Folin-Ciocalteu method standardized in ISO 14502-1, measure total phenolic content by reacting polyphenols with reagents to produce measurable absorbance, though they overestimate due to interference from non-phenolic reductants. Near-infrared (NIR) spectroscopy provides non-destructive, rapid screening of polyphenols, caffeine, and amino acids in intact leaves or infusions, correlating spectral data with reference HPLC values via partial least squares regression for quality grading without sample preparation. Sensory evaluation by trained tasters complements chemical analysis, assessing attributes like briskness and astringency, which correlate with theaflavin content (typically 1-6% in high-quality black tea) and infusion color brightness measured via spectrophotometry. Key quality indicators include catechin profiles for green tea, where EGCG levels exceeding 50 mg/g dry weight signal premium antioxidant capacity and freshness, while degraded catechins indicate over-withering or poor storage. In black tea, theaflavins (formed via catechin oxidation) and thearubigins determine liquor strength and redness, with optimal ratios (theaflavins:thearubigins ≈ 1:10) linked to superior taste by expert panels. Caffeine content, standardized at 20-40 mg/g in most teas via HPLC, influences bitterness but serves more as a consistency check than a premium marker. Variations in these indicators reflect terroir and processing; for instance, high-altitude teas exhibit elevated catechins due to stress-induced biosynthesis. International standards from and guide these analyses for trade grading, prioritizing empirical thresholds over subjective aesthetics.

Health Effects

Supported benefits from meta-analyses

Meta-analyses of prospective cohort studies have found that moderate tea consumption, typically 2-3 cups per day, is associated with reduced risks of all-cause mortality, cardiovascular disease mortality, and type 2 diabetes incidence, with dose-response relationships indicating greater benefits at higher intakes up to approximately 4 cups daily. These associations persist across green and black teas, though green tea shows stronger effects in randomized controlled trials for certain biomarkers. An umbrella review of 15 meta-analyses confirmed inverse associations for total mortality (relative risk 0.92 per 3 cups/day), cardiac death, coronary artery disease, and stroke, attributing potential mechanisms to tea polyphenols' antioxidant and anti-inflammatory properties. For cardiovascular risk factors, green tea supplementation significantly lowers systolic blood pressure by an average of 1.98 mmHg (95% CI: -2.94, -1.01) and diastolic by 1.92 mmHg (95% CI: -3.17, -0.68) in meta-analyses of randomized trials involving adults with or without hypertension, with effects more pronounced in those with elevated baseline levels. Black tea consumption similarly reduces blood pressure modestly, with systematic reviews reporting decreases of 1.8/1.4 mmHg for systolic/diastolic after regular intake over 4 weeks or more. Lipid profiles improve with green tea, as evidenced by meta-analyses showing reductions in total cholesterol by 4.67 mg/dL and LDL cholesterol by 4.55 mg/dL, without significant changes in HDL or triglycerides, particularly in individuals with hyperlipidemia. Glycemic control benefits are supported for green tea in short-term interventions, with meta-analyses of randomized trials demonstrating lowered fasting blood glucose levels (mean difference -0.09 mmol/L), though effects on fasting insulin and HbA1c are inconsistent and limited to durations under 3 months. Cohort-based meta-analyses link higher tea intake to a 17% lower risk of type 2 diabetes, potentially via catechins' enhancement of insulin sensitivity. Evidence for cancer risk reduction remains weak overall, with prospective meta-analyses finding no consistent inverse association across sites, except modest protection against lymphoid neoplasms from green tea (RR 0.95). These benefits are observational in nature for mortality outcomes and require caution due to confounding by lifestyle factors in tea drinkers.

Identified risks and limitations

Consumption of tea, particularly in excess, can inhibit non-heme iron absorption due to polyphenols such as tannins, which bind to iron in the gastrointestinal tract and reduce bioavailability by approximately 60-70% when tea is consumed simultaneously with iron-containing meals. This effect is more pronounced with and poses a risk for iron deficiency anemia in populations reliant on plant-based diets or those with marginal iron status, such as women of childbearing age or individuals in developing regions with high tea intake. A one-hour interval between tea consumption and iron-rich meals mitigates but does not fully eliminate this inhibition. Caffeine in tea, typically 20-60 mg per cup depending on type and brewing, may exacerbate anxiety, restlessness, and sleep disturbances in sensitive individuals, with meta-analyses indicating an elevated risk of anxiety symptoms even at moderate intakes among healthy adults without psychiatric disorders. Excessive intake exceeding 400 mg daily—achievable with 7-10 cups of —has been linked to potential cardiovascular strain, though evidence for overt adverse effects in healthy adults remains limited to observational data. Gastrointestinal issues like nausea and heartburn can also arise from high tannin content irritating the stomach lining. Tea leaves accumulate from soil, resulting in brewed concentrations of 1.6-6.1 mg/L, with black tea averaging 3-4 ppm; chronic high consumption (e.g., >4 liters daily) elevates risks of in children and in adults, as documented in case reports of tea-dependent individuals developing and rigidity. Pregnant women consuming multiple cups daily may increase fetal risks via elevated maternal fluoride exposure. Oxalate content in tea, particularly varieties, contributes to urinary oxalate excretion, potentially heightening stone formation in predisposed individuals, though prospective studies show no overall increased incidence in general populations and mixed on risk elevation versus dilution by tea's fluid volume. Epidemiological studies on tea's effects often rely on self-reported and suffer from by factors (e.g., tea drinkers' healthier diets or exercise habits), reverse causation, and heterogeneity in tea types, preparation, and bioavailability, limiting causal inferences. Inconsistent results across cohorts, particularly for cancer and cardiovascular outcomes, underscore the need for randomized controlled trials to disentangle benefits from risks, as observational associations may overestimate protective effects due to unmeasured variables. Contaminants like pesticides or in low-quality teas further complicate assessments, varying by origin and processing. Tea plants absorb heavy metals such as lead from the soil through their roots; matcha, involving consumption of the whole ground leaf rather than an infusion, may result in higher exposure compared to steeped teas.

Consumption guidelines and confounding factors

Moderate consumption of tea, typically defined as 2-3 cups (approximately 470-710 ml) per day, has been associated in observational studies with reduced risks of , , , and premature mortality. For specifically, intakes of 3-5 cups daily appear optimal for maximizing potential benefits from catechins, though evidence from randomized controlled trials remains limited compared to epidemiological data. Total caffeine intake from tea and other sources should not exceed 400 mg daily for healthy adults, equivalent to roughly 5-6 cups of (about 71 mg per 240 ml cup) or 10-12 cups of (about 37 mg per cup), to avoid adverse effects like or jitteriness. Excessive intake beyond 3-4 cups daily may lead to risks including reduced iron absorption due to polyphenols binding minerals in the gut, particularly problematic for individuals with low iron stores or those consuming tea with meals. Very high doses exceeding 10 g of caffeine (far beyond typical tea consumption) can cause severe toxicity, though standard brewed tea rarely approaches this threshold. Pregnant individuals should limit to under 200 mg caffeine daily (about 2-3 cups of black tea) to minimize potential fetal risks, per guidelines from health authorities. Interpreting tea's health effects requires caution due to factors prevalent in observational research, where tea drinkers often exhibit healthier lifestyles—such as lower rates, better diets, and higher —independent of tea itself, potentially inflating apparent benefits. Residual persists even after statistical adjustments, and reverse may occur if healthier individuals self-select into tea consumption. Genetic variations in metabolism influence individual responses but do not fully explain observed associations, as benefits appear consistent across genotypes in some cohorts. Preparation methods (e.g., brewing time affecting extraction) and co-consumption with or further confound outcomes by altering , underscoring the need for randomized trials over correlational data to establish .

Preparation and Consumption

Brewing techniques and variables

Brewing tea involves extracting soluble compounds from leaves or processed forms using hot water, with techniques varying by cultural tradition and tea type to optimize flavor, aroma, and bioactive extraction. Western-style brewing typically employs a low leaf-to-water ratio of approximately 2 grams of tea per 500 milliliters of water, with infusion times of 2-5 minutes in a or , suitable for single infusions of , , or teas. In contrast, gongfu cha, originating from practices in the 18th century and popularized in during the 1970s, uses a high ratio of 5-7 grams per 100-150 milliliters, multiple short steeps of 10-60 seconds in a or small , allowing progressive flavor release across 5-10 infusions, particularly for and pu'er teas. Japanese methods, such as for , emphasize precise temperatures around 70-80°C for 1-2 minutes to preserve delicate and avoid bitterness, while is whisked into suspension rather than steeped. Water temperature critically influences extraction rates and compound profiles; temperatures below 80°C favor catechins in , minimizing release that causes astringency, whereas black teas benefit from 95-100°C to fully solubilize theaflavins and thearubigins. time and temperature exhibit an inverse relationship: shorter durations at higher temperatures or longer at lower ones yield comparable extraction, but exceeding optimal parameters—such as 3 minutes at 85°C for —can degrade (EGCG) levels while increasing bitterness. Leaf-to-water ratio affects concentration; higher ratios in gongfu brewing concentrate flavors per but require shorter times to prevent over-extraction. Water quality variables, including mineral content and , modulate infusion outcomes: low (TDS) and weakly acidic water ( 5-7) enhance extraction for non-fermented teas like , while harder water may dull flavors in delicate varieties. influences kinetics, with finer leaves or broken grades extracting faster than whole buds, necessitating adjusted times to avoid imbalance. Agitation during accelerates , and sequential infusions in methods like gongfu exploit per steep, preserving nuanced profiles across brews. Empirical studies confirm that parameters like 100°C for 5 minutes optimize potential in , underscoring the need for type-specific adjustments to balance sensory and health attributes.

Packaged and ready-to-drink forms

Packaged teas encompass forms designed for convenience, including tea bags and instant powders, which allow rapid preparation without loose leaves. Tea bags originated in 1908 when New York tea merchant Thomas Sullivan distributed samples in small pouches, leading customers to brew the tea directly in the bags rather than emptying them. This accidental innovation evolved with the 1930 patent for heat-sealed paper fiber tea bags by William Hermanson, followed by the rectangular shape's introduction in 1944. Modern tea bags vary in materials, such as biodegradable paper, mesh for better infusion, or shapes that permit leaf expansion akin to loose tea. Instant tea, a dehydrated form, emerged in the late with a 1885 patent for converting tea into a paste reconstituted by hot water, though commercial viability grew in the mid-20th century, particularly during for military rations. Production involves extracting soluble solids from leaves or waste via hot water infusion, concentrating the liquor, and spray- or freeze-drying it into powder or granules. This method prioritizes shelf stability and speed but often results in diminished flavor compared to steeped tea due to loss of volatile compounds during processing. Ready-to-drink (RTD) teas, pre-brewed and bottled or canned, gained prominence in the late alongside the rise of convenience beverages, often featuring iced varieties with added flavors, sugars, or preservatives. The global RTD tea market reached USD 34.10 billion in 2024, driven by demand for portable, health-oriented options like unsweetened variants, with projections estimating growth to USD 59.93 billion by 2034 at a 5.80% . Packaging typically employs PET bottles or aluminum cans to maintain freshness and enable cold-chain distribution, though formulations vary widely, from authentic cold-brew extracts to tea-flavored sodas with minimal tea content.

Cultural rituals and global customs

In , the gongfu cha preparation method, originating in the region during the 18th century and popularized in its modern form through in the 1970s, emphasizes multiple short infusions using small clay teapots and a high leaf-to-water to extract nuanced flavors from or other teas. This ritual focuses on the sensory appreciation of tea's evolving taste across infusions, often shared in informal gatherings without the rigid formality of Japanese practices, though it incorporates precise steps like rinsing leaves and warming vessels. Japan's chanoyu, or the way of tea, is a formalized Zen-influenced ceremony dating to the 16th century under masters like Sen no Rikyū, involving the whisking of powdered matcha green tea into froth served alongside a kaiseki meal in a minimalist teahouse. The multi-hour event progresses from thick koicha, shared from one bowl to symbolize equality, to thin usucha, embodying principles of harmony (wa), respect (kei), purity (sei), and tranquility (jaku), with guests entering through a low door to foster humility. British afternoon tea emerged in 1840 when Anna, the seventh Duchess of Bedford, began serving light refreshments including tea, sandwiches, scones with and jam, and pastries around 4 p.m. to alleviate hunger between and late dinners. This upper-class custom, later adopted widely, involves tiered stands for savories and sweets, with milk added to tea before water in some traditions to prevent curdling, reflecting post-17th-century adaptations of Chinese imports via . In , (çay) is brewed strong in a çayer (double teapot) and served diluted in tulip-shaped , a daily integral to since Ottoman times, where offering refills signals ongoing conversation in homes, bazaars, or men-only kıraathanes. Guests sip without milk, often holding saucers underneath, with strength gauged by color—darker for preference—and annual consumption exceeding 3 kilograms per person as of recent data. Morocco's atay bi nana, a infused with fresh and generous sugar, follows a pouring from height to create foam, served in three progressively stronger rounds symbolizing life's bitterness turning to sweetness, prepared by the male host as an act of refined . This Berber-influenced custom, introduced in the , mandates ornate silver pots and small glasses, with refusal seen as discourtesy. Russian tea customs revolve around the , a metal heating water since the early , used to dilute a potent zavarka into glasses, traditionally sipped through a sugar lump held between teeth or with for contrast. This communal practice, peaking in the late 1800s with samovars producing up to two gallons, fosters extended social talks across generations, often without milk. India's , boiled with milk, , spices like and ginger, and , evolved from 19th-century British influences but became a mass ritual post-1950s when plantations expanded, with chaiwalas street-vending it as a social lubricant for daily interactions and breaks. Preparation involves multiple boils for , served hot in earthen kulhads or glasses, embedding it in routines where per capita intake reached 0.75 kilograms yearly by the .

Economics

Major producers and supply chains

China produces the largest share of the world's tea, accounting for over 50% of global output in 2024, with production reaching approximately 3 million metric tons, marking a 5% increase from 2023 driven by expanded cultivation in provinces such as , , and . India's output follows at around 1.3 million metric tons annually in recent years, concentrated in regions like and , where dominates for both domestic consumption and export. ranks third with about 500,000 metric tons, primarily from highland smallholder farms, while produces roughly 300,000 metric tons, focusing on Ceylon black teas from central plantation estates. Other notable producers include (250,000-300,000 metric tons), (250,000 metric tons from the Black Sea region), and (150,000 metric tons), with global production totaling around 6.5 million metric tons in 2024.
CountryApproximate Production (2024, metric tons)Primary Types
3,000,000Green, ,
1,300,000 (Assam, )
500,000
300,000 (Ceylon)
280,000,
Tea supply chains typically begin with cultivation of on plantations or smallholder plots in tropical or subtropical highlands with acidic soils and high rainfall, followed by hand or machine plucking of shoots (), withering to reduce moisture, rolling to break cell walls, oxidation (for teas), firing or to halt enzymes, and sorting into grades by size and quality. In , chains emphasize artisanal processing for specialty greens and oolongs, with much production consumed domestically via state-supported cooperatives and private gardens, though exports of low-grade s and greens occur through ports like ; vertical integration by firms limits intermediaries, but quality varies due to decentralized standards. India's chains involve large estates and auctions in and , where brokers sell to packers and blenders for export to markets like the and ; the regulates standards, but challenges include weather-dependent yields and broker opacity. Kenya's model relies on over 600,000 smallholders organized under the Kenya Tea Development Agency (KTDA), who deliver green leaf to factories for orthodox or CTC (cut-tear-curl) processing, followed by sale at the Tea Auction—the world's largest by volume—enabling exports of uniform to , , and via efficient logistics, though farmer payments depend on global prices. Sri Lanka's estate-based chains, managed by companies like and , process leaves at on-site factories and auction in , exporting high-grown orthodox teas to the and , with traceability emphasized but vulnerable to labor and pest issues. In export-heavy nations like and Sri Lanka, chains prioritize volume and standardization for blending, contrasting China's focus on varietal diversity, while global shipping via bulk containers or bags handles the bulk of trade, with , , and leading exports by value (each around $1.4 billion in 2023 data).

Global trade volumes and values

In 2023, global tea exports totaled approximately 1.8 million metric tons, primarily consisting of , with a trade value of around USD 9.5 billion. accounted for the majority of traded volume, driven by demand in regions like the , , and , while exports remained smaller at roughly 200,000-300,000 metric tons annually. Trade volumes have grown steadily since the early 2000s, increasing from about 1.2 million metric tons in 2004, though growth slowed in 2023 due to supply disruptions in key producers like and fluctuating auction prices. Kenya led global tea exports in 2023 with 545,574 metric tons of black tea valued at USD 1.3 billion, benefiting from efficient large-scale production and auction systems in . followed with 135,669 metric tons worth USD 619 million, focusing on orthodox and CTC varieties for markets in the and . , despite being the largest producer, exported around 300,000-375,000 metric tons valued at USD 1.26 billion, primarily green teas to destinations like and the . Other notable exporters included (limited net exports due to high domestic consumption), , and , contributing smaller but growing shares through bulk black tea shipments.
Top Tea Exporters (2023)Volume (metric tons, black tea)Value (USD million)
545,5741,300
135,669619
~300,000 (total tea)1,260
Imports were dominated by , which imported USD 634 million worth of tea to meet domestic demand exceeding local production. The followed with USD 578 million, sourcing primarily from , , and for both black and specialty teas. The imported USD 377 million, relying on Kenyan and black teas for blending and re-export. Other major importers included the (USD 372 million, as a regional hub) and , with trade flows influenced by geopolitical factors like sanctions affecting Russian volumes. Overall, developing economies in and the absorbed over 50% of global imports by value, reflecting tea's role as an affordable staple beverage.
Top Tea Importers (2023)Value (USD million)
634
579
377
372
Tea trade values are typically lower per unit than other beverages due to , with average prices around USD 4-5 per for , though premium segments like orthodox teas command higher rates. Re-exports from hubs like and add 10-15% to global volumes, facilitating distribution to secondary markets in .

Recent market dynamics and forecasts

Global tea production reached approximately 6.7 million metric tons in 2023, with a marginal increase from prior years driven by recoveries in regions like , though 2024 saw persistent oversupply pressures amid variable weather impacts on key producers such as and . Demand for premium and specialty teas, including and functional varieties, has bolstered segments resistant to bulk commoditization, while overall production grew modestly at around 2.1% annually. Supply chain challenges, including elevated shipping costs post-pandemic and labor shortages, compounded by climate variability, have elevated production expenses, contributing to price volatility despite global surpluses. Tea prices exhibited upward momentum in late 2024 and into 2025, with auction averages climbing to 197.41 INR per kg by October 18, 2025, reflecting a 4.47% monthly rise amid localized shortages and input cost , though year-over-year declines persisted due to oversupply. In the U.S., import volumes surged 29.36% to 89.58 thousand tons in 2024, signaling robust consumer demand amid expansion, yet tariff threats and geopolitical tensions posed risks to trade flows from major exporters like . Forecasts project the global tea market to expand at a of 5.5% to 7.4% through 2030, potentially reaching $92 billion by then, fueled by health-driven consumption of functional and ready-to-drink formats, premiumization in emerging markets, and demands. Challenges such as climate-induced yield fluctuations and potential trade barriers may temper growth, with analysts emphasizing diversification into high-value segments to mitigate commoditized bulk tea vulnerabilities.

Issues and Controversies

Labor practices and claims

![Tea workers harvesting in Sri Lanka](./assets/SriLanka_TeaHarvest_pixinn.netpixinn.net Tea production depends heavily on manual labor, with an estimated 13 million workers employed on plantations worldwide, many facing allegations of substandard wages, excessive hours, and inadequate living conditions. In major producing regions, pluckers—predominantly women—perform repetitive tasks under exposure to , pesticides, and ergonomic strains, leading to documented health issues including musculoskeletal disorders and respiratory problems from dust . In India's Assam region, tea workers receive wages insufficient for basic nutrition, with reports indicating malnourishment and vulnerability to fatal illnesses due to poverty-level pay and subpar housing lacking sanitation and clean water. A 2024 living wage benchmark for Assam stands at ₹15,375 per month, yet actual earnings fall short, creating an 81% gap that perpetuates cycles of debt and poor health outcomes, including elevated maternal risks during pregnancy from prolonged hours and limited medical access. Investigations have highlighted systemic denial of living wages and decent conditions, with some estates failing to provide shelter from rain or proper protective equipment, exacerbating occupational hazards. Kenyan tea pluckers in areas like face a 62% shortfall, with workers enduring long shifts from dawn to dusk amid reports of inadequate housing and health services. In and , similar patterns emerge, including low daily earnings under $1 in some cases, contributing to high rates among Bangladeshi pickers due to undernutrition and unhygienic estate living. Child labor risks persist in tea supply chains across and , with forced child labor noted in production by U.S. Department of Labor assessments, though comprehensive eradication remains challenged by remote estate locations and economic pressures. Human rights claims include gender discrimination, , and potential trafficking indicators in African tea regions, as flagged by organizations monitoring supply chains. Efforts like certifications aim to address these, but studies on Fairtrade tea in and indicate persistent gaps in wage improvements and worker protections. These issues stem from labor-intensive harvesting economics and historical estate systems tying workers to on-site housing, often without viable alternatives.

Environmental impacts and sustainability

Tea production contributes to , particularly in regions like and , where expanding plantations have cleared forests at rates of up to 30 km² annually in some historical periods, reducing and increasing . practices in these areas create "green deserts" that fragment habitats, exacerbating vulnerability to pests and climate variability. Intensive farming requires substantial water, with the green (rainfall used by crops) for 1 kg of dry tea estimated at around 294 liters, plus 10 liters of blue water (surface or ), though in drier regions like parts of amplifies depletion and competition with local needs. , often exceeding safe residue limits in exports from and , leads to runoff polluting waterways, degradation, and harm to non-target , with neonicotinoids persisting in ecosystems for years. Greenhouse gas emissions from tea cultivation average 10.4 to 15.6 kg CO₂ equivalent per kg of dry in , driven by use, machinery, and processing, while global supply chains add transport-related footprints. compounds these issues, with rising temperatures, erratic rainfall, and droughts projected to shrink suitable growing areas by 2050 in 11 of the top 20 producers, reducing yields by up to 20% in vulnerable zones like , , and increasing pest pressures. Sustainability initiatives include certifications like Rainforest Alliance, which promote integrated pest management, shade-grown systems, and waste recycling; Kenya has achieved near-total compliance, aiding soil health and emissions reduction through biomass energy. Organic practices and biochar from tea prunings offer viable alternatives to chemicals, potentially cutting pollution while maintaining yields, though adoption remains limited by costs and smallholder scale in major producers like India and Sri Lanka. Challenges persist, as global demand growth—over 2% annually—pressures land expansion without proportional shifts to verified sustainable sourcing.

Adulteration, safety, and regulatory challenges

Tea adulteration involves the addition of non-tea materials to increase volume or mimic appearance, such as mixing leaves from other plants like or incorporating fillers like and artificial powders. Artificial coloring agents, including Bismarck Brown, , dyes, and azo dyes, are commonly used to enhance visual appeal, particularly in lower-grade black teas. Historical precedents include 19th-century British scandals where merchants exhausted genuine tea stocks and manufactured fakes from leaves and fillers, leading to outcries and regulatory responses. Pesticide residues pose significant safety risks in tea, as leaves absorb chemicals applied during cultivation, with organochlorine pesticides like persisting despite bans in many regions. Studies indicate residues exceed maximum residue limits (MRLs) in samples from major producers, potentially transferring to infusions and causing neurotoxic, carcinogenic, or endocrine-disrupting effects upon chronic exposure. Heavy metal contamination, including lead and aluminum from or processing, occurs in teas like where cassava-based boba pearls contribute elevated levels, though brewing often reduces transfer to safe thresholds in conventional varieties. assessments generally find non-carcinogenic hazards low for typical consumption, with hazard indices below 1, but vulnerable populations like children face higher relative exposure. Regulatory challenges stem from varying international standards, with the enforcing stringent MRLs that result in frequent detections of banned pesticides in imported teas—up to 38% of tested samples containing prohibited substances like those in tea from non-EU producers. provides global guidelines, but enforcement gaps in producing countries lead to non-compliance, including export rejections for exceeding limits on residues from chemicals like . Disparities arise from "double standards," where producers avoid certain pesticides domestically but permit higher residues in imports, complicating trade for exporters from and who must navigate fragmented testing and certification. Weak in supply chains exacerbates issues, as adulteration evades detection without advanced methods like FT-IR or DNA testing.

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