Tea is the most popular and important beverage in the world. In China tea is a beverage known about for 3000 years. However, current distribution pattern of tea type originated in the area somewhere near ‘Irrawaddy basin’ from where it dispersed to South- East China, Indonesia and India. Tea grows at latitude 27° South (Argentina) to 42.43° North (Georgia) and from sea level up to altitude of 2500 m. The soil in which tea grow are widely alluvial (in Assam, India), podzols ( in USSR), volcanic ash ( in Japan), andosole (in Indonesia), red yellow podzols (in Taiwan), red soil ( in China) and sedimentary ( in Darjeeling, India). Tea are mosty cultivted from two varieties of Camelia sinensis and Camellia assamica. Other varieties include Camellia talienensis, Camellia irrawadinensis, Camellia gracilipes and Camellia pubicosta. In Theaceae family there are 82 varieteiss of tea plant. These varieties of tea leaves are produced and produced and processed to give black, green and oolong tea. Generally tea contains 23 – 26 % solid matters and 74 – 77 % moisture ( in tea leaves) but depends on seasons. Half of solid matter is insoluble in water that includes cellulose, lignin and lipids.
Composition of tea: The important constituents of the tea contributing to the flavor of tea beverage are caffeine, polyphenols and essential oils. The chemical composition of tea leaves are as follows
| Constituents | composition |
| Polyphenols | 36 % |
| Carbohydrates | 25 % |
| Protein | 15 % |
| Lignin | 6.5 % |
| Amino acids | 4 % |
| Methylxanthines | 3.5 % |
| Lipid | 2 % |
| Organic acids | 1.5% |
Source: (Turan & Kennedy, 2002)
Fresh tea leaves also contains carotenes B vitamins and ascorbic acid. During the manufacturing of black tea, ascorbic acid is lost. The production of chemical composition varies and generally depends upon variety of tea, condition of growing, circumstance of plucking and treatment during manufacturing.
Tea cultivation: There are about 45 species of Camellia sinensis. Commercially tea is obtained from plants propagated from seeds sown in nursery and cutting of plant can also be used. Tree bush for plucking regularly is pruned to obtain bush shape which encourages maximum leaf production. Among the cultivated Camellia sinensis there are of two types; China and Assam originated. The Chinese type is slow growing smaller tree with narrow leaves whereas Assam originated is fast growing with large leaves. Yield from Assamic variety is higher than Chinese type. Tea leaves are usually plucked by hands and in some places by using machines. The average plucking interval is about a week. Usually 1 bud and 2 leaves are plucked from end of each shoot for a good quality tea. In some cases, the bud and 3 leaves are plucked giving higher yield.
Types of tea:
Black tea: it is dominantly manufactured worldwide. It is made from fermented tea leaves. Fermentation in tea doesn’t mean actual fermentation. It is made through a polyphenol oxidase catalyzed oxidation of fresh leaf catechins. Black tea are further divided into two category as per their size and liquor color which are known as CTC and orthodox. The CTC tea is granular in type and orthodox is leafy.
Green tea: They are not fermented at all but merely withered in hot air and quick steamed and pan fried. A gentle rolling and heating stabilize the tea natural aroma and flavor. Applying heat to the green leaf prevent enzymatic oxidation of catechins as result of enzyme inactivation. Made tea is light green in color and bitter taste. Green tea is mostly consumed in Japan and China. Nowadays, green tea is perceived as having medicinal properties.
Oolong tea: It is partially oxidized or partly fermented tea. It is also called semi fermented tea. It is manufactures primarily in China and Taiwan. It gives distinct reddish color and flowery flavor.
White tea: it is highly oxidized tea, grown and harvested almost in China where tea comes from delicate buds and younger leaves of Chinese Camellia sinensis plant. These buds and leaves are allowed to wither in natural sunlight before they are lightly processed to prevent the further fermentation. This preserve the characteristic flavor of white tea. White tea is derived from fine silvery white hairs un-open buds of the tea plant which gives the tea whitish appearance. White tea has now become a more widely available, often being sold as ‘silvery tip’ and ‘pekoe’ a form of its traditional name and now also known as ‘China white’. White tea contains high level of catechins, a polyphenol compound that is responsible for lessening atherosclerosis, plaque, reducing carcinogen, reducing risk of stroke and diabetes.
Early grey: Charles second Early Gray was British Prime minister. The ‘Bergamot orange’ is the flavoring used in ‘Early gray’ tea. Oil of Bergamot is extracted from the peel of Bergamot orange, a small pear shaped sour orange which is cultivated today mostly in Southern Italy. But its origin is in Vietnam and Southern China.
Billy tea: Billy is a metal can with a wire handle. Early Australian settlers when arrived in Australia brewed their tea in a Billy and the name came from this container.
Darjeeling tea: It is a protected brand name defined by Tea Board of India. Darjeeling lies in West Bengal state of India. The prevailing cool and moist climate and unique geographical terrain makes the Darjeeling tea a unique ‘muscatel flavor’. In general quality of Darjeeling tea is characterized by the presence of higher level of monoterpenes and differs significantly with Assam tea. The characteristics of muscatel flavor is reported to be associated mainly with 2-6 Dimethyl.
Orange Pekoe: this is black tea which is prepared from two youngest leaves from new flush pekoe, was originated from the Chinese word ‘Baihao’ which means the white up that has unfolded leaf bud. But the use of orange in front of Pekoe is assumed that such tea were first presented to Royal family of Holland, which used to be told as house of oranges. To promote the tea in in market and traders, use of term orange pekoe was used to make association with Royal family.
References:
Turan, N., & Kennedy, J. F. (2002). Phytochemicals as Bioactive Agents.
About Author
Name : Pratiksha Shrestha
pratiksha.shrestha2001@gmail.com
Ms. Shrestha holds masters degree in food engineering and bioprocess technology from Asian Institute of Technology (AIT) Thailand. She is currently working for Government of Nepal at Department of Food Technology and Quality Control (DFTQC), Kathmandu. She is also a teaching faculty in College of Applied food and Dairy Technology (CAFODAT) affiliated to Purbanchal university, Nepal.