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The botanical name of the tea plant is Camelia sinensis. Tea is an evergreen plant belonging to the theceae family of the genus Camelia. Tea is a liquid refreshment prepared by the infusion of leaf in the water. Tea is a beverage consumed up to about 3800 million kg per year, hence tea is known as the queen of beverage. Tea is derived from the Chinese term ‘cha’. In early days, tea was used as an herbal drink, and later it became a beverage. Tea cultivation started from 2700 B. C.
In the early 19th century, tea plant was found growing in the forest of Assam. In 1823, Robert Bruce found tea growing in abundance at the hill top of upper Assam. Thomas Sullivan, a New York merchant, invented tea bags in the early 20th century.
White tea, yellow tea, green tea, oolong, dark tea, and black tea are all made from one of two major varieties grown today, C. sinensis var. sinensis and C. sinensis var. assamica, but are processed differently to achieve different levels of oxidation, with black tea being the most oxidized and green tea being the least.
Kukicha (twig tea) is also made from C. sinensis, but instead of leaves, it uses twigs and stems. In India, tea is cultivated in Assam, Kerala, Karnataka, Darjeeling, West Bengal, etc.
Kingdom − Plantae
Phylum − Spermatophyta
Subphylum − Angiospermae
Class − Dicotylydonea
Order − Theales
Family − Theceae
Genus − Camellia
Species − C. sinensis
Tea is a woody shrub and can reach up to the height of 9–15 m, but they are trimmed about 1–2 m for cultivation. Leaf of tea plants are broad, simple, alternate with oval or elliptical shape with variegated margins. White hairs can be found on the underside of the leaf.
Tea is classified into two based on the size of leaf present in it −
Assam type− Plant with longer leaf.
China type− Plants with smaller leaf.
The young tea leaves contain oil glands, which imparts a characteristic smell and aroma. The tea plant blooms once in a year, that is, right before the plant produces seeds and its winter hibernation. The flowers are scented, white/pink, borne in the axils of the leaves individually or in clusters. It has brownish green fruits with a trilocular capsule containing one brown, round or flattened seed in each locule.
This plant grows in the tropical and subtropical highlands.
These plants want a deep, well-drained loam soil or forest area to flourish in. It requires temperatures of 24–30 degrees Celsius and 100–150 cm of yearly rainfall.
Tea plant growth is not suited to prolonged periods of drought. Seeds are used to grow the plants. In roughly a year, seedlings produced in nurseries are ready for transplantation.
To encourage branching, the plant is trimmed to 45–50 cm when it reaches a height of 2 meters. The plant requires regular pruning and harvesting of new leaves after reaching a certain growth “plucking level.”
The growth of the tea plant is not consistent throughout the year. A time of tremendous growth is followed by a period of dormancy. The flush is the development of new leaves on a regular basis. Plucking takes place throughout the year in South India. Plucking occurs three to four times a year in North India. Because the plant is dormant throughout the winter, plucking is not done during this time.
Hands or scissors are used to harvest leaves. Typically, plucking is done by women. Terminal bud, young delicate shoots, and 2 to 5 leaves are plucked immediately before being moved to a basket dangling from the trash. Every day, a skilled worker can pluck up to 50 kg of tea leaves. The age of the leaf determines its quality.
Withering is the process of removing moisture from the leaves. Fresh leaves have a moisture level of 75 percent. Leaves are strewn on withering racks for 12-18 hours. When hot air is blown over the racks, the leaves soften and become ready for rolling.
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In this method, special machines twist and compress the leaves. To obtain totally dried leaves with a dull green color, the fluids are exposed to air for fermentation, resulting in green unfermented tea.
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It is carried out in a fermentation chamber with controlled temperature, humidity, and aeration. Polyphenol is broken down by an enzyme called polyphenol oxidase, which produces ‘orthoquinone,’ which gives the leaves their black color.
Tea fermentation takes three hours, and the tea that has been fermented the longest is soft and darker in color, while the tea that has been fermented the shortest is more pungent. Fermentation produces a bright crimson color and a distinct scent.
Drying is done in a specialist oven with heated air at 1000°C for 20–25 minutes to end fermentation. The product is black in colour after drying and has a pungent smell.
To divide leaves into smaller and larger pieces, mechanically oscillated sieves are used. Broken Orange Pekoe (BOP), Flowery Broken Orange Pekoe (FBOP), Orange Pekoe (OP), and other tea grades exist.
Caffeine is a secondary metabolite produced by Camelia sinensis that acts as a natural pesticide by paralyzing and killing predator insects feeding on the plant. Caffeine is a purine alkaloid whose manufacture is regulated by numerous enzymes and found in young tea leaves. Other caffeine-producing plants, such as coffee or Guayas, have a different biosynthetic pathway than C. sinensis. The mechanism was investigated by extracting young leaves and analysing the genes encoding the key enzymes involved in caffeine synthesis using reverse transcription PCR. Caffeine synthase is encoded by the TCS1 gene. TCS1 transcripts are abundant in younger leaves, allowing more caffeine to be produced at this time.
The committed step is dephosphorylation of xanthosine-5’-monophosphate into xanthosine. Xanthosine is converted to 7-methylxanthosine, 7-methylxanthine, theobromine, and finally caffeine by a series of processes.
Q1. Which of the following is not a step in the production of black tea?
a. Drying
b. Withering
c. Lump formation
d. Rolling
Ans: Lump formation
Q2. A tea is pruned and preserved at a substantial height to be picked by the tea pluckers on a plough table.
a. True
b. False
Ans: True
Q3. ------------ is the process of removing moisture from the leaves.
Ans: Withering
Q4. Poly phenol is broken down by the enzyme --------------.
Ans: Poly phenol oxidase
Q5. The ----------- is the development of new leaves on a regular basis.
Ans: Flush
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