Cultivation, collection and processing of tea. Classification by oxidation state

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Let's start with terminology. Tea is a drink obtained by boiling, brewing and/or infusing tea leaves, which are previously prepared in a special way. Tea is also called the leaf of the tea bush itself, processed and prepared for making a drink. Sometimes the word "tea" is also used as the name of the tea bush (a plant species of the Camellia genus of the Tea family).

In a broad sense, tea is any drink made by brewing pre-prepared plant material. In the names of such drinks, the word "tea" is usually accompanied by an explanation characterizing the raw materials used ("herbal tea", "berry tea", "fruit tea" and so on).

Tea was originally used as a medicine. Its use as a drink became widespread during the Chinese Tang Dynasty (618–907 AD). It was in China that tea was first consumed, and it is from the Chinese name for tea (“te” in southern dialects, “cha” in northern dialects) that the names of tea in different languages \u200b\u200bare derived, and the choice of northern or southern pronunciation indicates the predominant method of tea delivery: respectively, by land or by sea.

In the middle of the 17th century, the Portuguese, the Dutch and the British began to carry tea from China to Europe. Initially, the tea became known as a medicinal drink, but as the decades passed, it was taken for pure enjoyment.

Cultivation, collection and processing of tea. Classification by oxidation state

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Cultivation and collection

The raw material for making tea is the leaves of the tea bush, which is grown in large quantities on special plantations. For the growth of this plant, a warm climate with a sufficient amount of moisture that does not stagnate at the roots is necessary. Most tea plantations are located on mountain slopes in areas with a tropical or subtropical climate.

In China, India and Africa, where the largest share of tea is produced, the collection is carried out up to four times a year. The teas of the first two harvests are most valued. The northern border of the territory where tea cultivation is economically justified runs approximately at the latitude of the former southern Soviet republics (Azerbaijan, Georgia) or the Krasnodar Territory of Russia. In higher latitudes, the tea bush can still grow, but it is unprofitable to cultivate it for the purpose of harvesting tea.

The tea leaves are picked and sorted by hand:

  • for teas of the highest grade category, unblown or blossoming buds and the youngest leaves are used, only the first or second flush (the first or second group of leaves on the shoot, counting from the end);
  • more "coarse" teas are made from mature leaves.
  • The work of pickers is quite hard and monotonous: the ratio of the mass of finished black tea and raw leaf is about ¼, that is, it takes four kilograms of leaf to make a kilogram of tea. The production rate for pickers is 30-35 kg of leaves per day, despite the fact that it is necessary to comply with quality standards and take only the necessary leaves from the bushes.

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    wikipedia.org

    Cultivation, collection and processing of tea. Classification by oxidation state

    wikipedia.org

    Cultivation, collection and processing of tea. Classification by oxidation state

    wikipedia.org

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Raw materials for high-grade teas often grow on small plantations (of about 0,5 hectares) located scattered on mountain slopes, so that the need to move from one plantation to another is added to the assembly of the leaf.

    Modern industrial plantations tend to be large enough to ensure continuity of picking and increase productivity, and the leaf harvested from these plantations is used for mass-produced tea.

    The need for manual picking limits the possibilities of tea cultivation: it makes sense only in regions with a sufficiently high productivity and a sufficiently low cost of manual labor of pickers.

    Repeated attempts were made to mechanize the assembly and sorting of tea leaves, in particular, in the USSR, a mechanized tea-harvesting unit was created back in 1958, but the technology of mechanized assembly has not yet been finalized: the leaf collected by combines is of too low quality, mainly due to the large number of outsiders. inclusions (shoots, dried leaves, foreign debris, and so on). So this method is used either for the production of the lowest grade tea, or in the pharmaceutical industry, for subsequent processing in order to isolate caffeine and other substances contained in tea.

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    Background photo created by fanjianhua – www.freepik.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    It is possible to grow tea in an ordinary apartment.

    After harvesting, the tea leaf is processed in a special way.

     

    Tea processing

    Making tea from the leaf of a tea bush usually involves the following steps:

    1. leaf drying at a temperature of 32–40 °C for 4–8 hours, during which the tea leaf loses some of its moisture and softens;
    2. repeated twisting by hand or on rollers, in which part of the juice is released;
    3. enzymatic oxidation, commonly referred to as fermentation, which breaks down the starch in the leaf into sugars and the chlorophyll into tannins. During fermentation, catechins are converted to theaflavin and thearubigins, which are orange and brown;
    4. drying at a temperature of 90-95 °C for black tea and 105 °C for green tea, which stops oxidation and reduces the moisture content of tea to 3-5%;
    5. cutting (except for whole-leaf teas);
    6. sorting by the size of tea leaves;
    7. possible additional processing and addition of additives;
    8. packaging.

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

    Cultivation, collection and processing of tea. Classification by oxidation state

    pixabay.com

     

    Classification of teas according to the degree of oxidation

    The appearance, aroma, taste of the infusion and other characteristics of tea are largely determined by how long and in what mode the enzymatic oxidation of the tea leaf is carried out before final drying.

    The classification of teas according to the degree of oxidation is ambiguous, since the Chinese terminology is somewhat different from that used in Europe and America.

    There are two main categories of tea, depending on the degree of oxidation:

    • Green tea – non-oxidized or slightly oxidized (it has the name "green" in all classifications). The leaves are pre-fixed with steam at a temperature of 170-180 °C (but not necessary). Oxidation is either not carried out at all, or lasts no more than two days, after which it is forcibly stopped by heating: (traditionally in pots, as is customary in China, or under steam, as is customary in Japan). Tea is oxidized by 3-12%.

    In dry form, such tea has a green color (from light green to dark green, depending on the characteristics of manufacture), the tea infusion is of a dull yellowish or greenish color, a “herbal” note is clearly distinguished in the aroma (it may be similar to the smell of dry hay), the taste is tart, it can be slightly sweet (but not bitter – only low-quality or incorrectly brewed, in particular, over-aged green teas, are bitter).

    Read more about green tea in our article ☛

  • Black tea is highly oxidized (the name "black" is European, it is also used in America, India and Sri Lanka. In China and other countries of Southeast Asia, such tea is called "red"). The leaves go through a long oxidation, from two weeks to a month (there are shortened processes when tea is oxidized during other technological operations, but they give a product of poorer quality due to the difficulties of controlling the process). The leaf is oxidized almost completely (by 80%).
  • When dry, the tea is dark brown or almost black in color. Infusion of tea – from orange to dark red. The aroma may have floral or honey notes, the taste is characteristic, tart, not bitter.

    Read more about black tea in our article ☛

    Other teas are in the degree of oxidation between black and green, or are distinguished by some technological features of preparation. All of the following types of teas are produced mainly in China or Taiwan.

    • White tea is a tea made from tips (unopened tea buds) and young leaves that has undergone a minimum number of processing steps in the production process (usually only withering and drying). Despite the name, white tea has a higher oxidation state (up to 12%) than most green teas. Among white teas, there are pure tips and those made from a mixture of tips and leaves.

      When dry, it has a light, yellowish color. Since the leaves are not subjected to twisting, tea leaves are quite large and light, they quickly open in water. The infusion is yellow-greenish, darker than the infusion of green teas (due to the higher degree of oxidation). The infusion has a floral aroma, a sweetish taste and leaves a pleasant, sweetish aftertaste. White tea is very sensitive to the brewing regimen.

      Read more about white tea in our article ☛

       

    • Yellow tea is oxidized by 3–12%, almost like green tea, but before drying, it undergoes a closed “languishing” procedure. Such teas are considered elite. Some varieties of yellow teas were previously produced exclusively for the imperial court and were banned from export from China.

      Read more about this tea in our article ☛

    • Oolong (in China it is sometimes called "turquoise" or "blue-green") – oxidation lasts from two to three days, reaching 30-70%. The appearance and characteristics of oolongs are highly dependent on the technology and the specific degree of oxidation, but all oolongs have a very characteristic taste that does not allow them to be confused with other types of teas.

    Read more about this tea in our article ☛

  • Puer is one of the most expensive teas in the world. It is made from both buds and mature leaves from old trees. According to the method of preparation, it is divided into Shu Puer (artificially aged, cooked) and Sheng Puer (raw, green). Initially brought to the state of green tea, after which they undergo a microbial fermentation procedure. Natural aging is carried out for several years without additional processing (sometimes called "aging"), artificial – by accelerating fermentation under conditions of high temperature and humidity.
  • Unlike other types of teas, pu-erh is not only oxidized, but also fermented in the exact sense of the word. The degree of oxidation of shu pu-erh is constant, it is determined by the variety and technology, and is usually quite high (not lower than that of oolongs). The oxidation of sheng pu-erhs changes with age, and if the "young" pu-erh is oxidized by only a few percent, then the "old" puerh can be oxidized by several tens of percent. The same tea, as it ages, gives an infusion of a significantly different appearance, aroma and taste.

    Read more about this tea in our article ☛

    Cultivation, collection and processing of tea. Classification by oxidation state

    wikipedia.org

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