The International Tea Day was observed on Thursday (December 15) in the tea-producing countries. Celebrated since 2005 in countries like Bangladesh, Sri Lanka, Nepal, Vietnam, Indonesia, Kenya, Malawi, Malaysia, Uganda, India and Tanzania, the Day aims to draw global attention of Governments and citizens to the impact of the global tea trade on workers and growers and has been linked to requests for price support and fair trade.
Tea is an aromatic beverage commonly prepared by pouring hot or boiled water over cured leaves of the Camellia sinensis (botanical name of tea shrub), an evergreen shrub native to Asia.
After water, it is the most widely consumed drink in the world. There are many different types of tea; some teas, like Darjeeling and Chinese greens, have a cooling, slightly bitter, and astringent flavour, while others have vastly different profiles that include sweet, nutty, floral or grassy notes.
Tea originated in southwest China, where it was used as a medicinal drink. 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. During the 17th century, drinking tea became fashionable among Britishers, who started large-scale production and commercialisation of the plant in India to bypass the Chinese monopoly. The Britishers launched a tea industry by offering land in Assam to any European who agreed to cultivate it for export.
Tea was introduced into India by the British in an attempt to break the Chinese monopoly on tea. In 1841, Arthur 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. The largest producers of tea are the People’s Republic of China, India, Kenya and Sri Lanka.
Camellia sinensis is an evergreen plant that grows mainly in tropical and subtropical climates. 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. In addition to a zone 8 climate or warmer, tea plants require at least 127 cm (50 in) of rainfall a year and prefer acidic soils. Many high-quality tea plants are cultivated at elevations of up to 1,500 m (4,900 ft) above sea level. Though at these heights the plants grow more slowly, they acquire a better flavour. A tea plant will grow into a tree of up to 16 m (52 ft) if left undisturbed, but cultivated plants are generally pruned to waist height for ease of plucking. Also, the short plants bear more new shoots which provide new and tender leaves and increase the quality of the tea. Only the top 1-2 inches of the mature plant are picked. These buds and leaves are called ‘flushes’. A plant will grow a new flush every seven to 15 days during the growing season. Leaves that are slow in development tend to produce better-flavoured teas. Six different types of tea like white, yellow, green, oolong, black and post fermented are processed.
A food safety management group of the International Organisation for Standardisation (ISO) has published a standard for preparing a cup of tea.
The order of steps in preparing a cup of tea is a much-debated topic, and can vary widely between cultures or even individuals. Some say it is preferable to add the milk before the tea, as the high temperature of freshly brewed tea can denature the proteins found in fresh milk. Others insist it is better to add the milk after brewing the tea, as black tea is often brewed as close to boiling as possible. The flavour of the tea can also be altered by pouring it from different heights, resulting in varying degrees of aeration.
Caffeine constitutes about 3 per cent of tea’s dry weight, translating to between 30 mg and 90 mg per 8-oz (250-ml) cup depending on type, brand, and brewing method. A study found that the caffeine content of 1 g of black tea ranged from 22 to 28 mg, while the caffeine content of 1 g of green tea ranged from 11 to 20 mg, reflecting a significant difference. Tea also contains small amounts of the obromine and the ophylline. Fresh tea leaves in various stages are stimulants, and xanthines similar to caffeine.
Drinking tea has many health benefits. Studies claim that the polyphenol content of green tea has antioxidant properties that can help prevent cancer; however research is on. There is also a suggestion that it can increase endurance in exercise by improving fat metabolism. Tea contains antioxidants which prevents ageing. Tea may reduce risk of cardiac arrest. Tea could be beneficial to people with Type 2 diabetes. Studies suggest that compounds in green tea could help diabetics’ better process sugars. Tea might be an effective agent in the prevention and treatment of neurological diseases, especially degenerative diseases (Alzheimer’s). While many factors influence brain health, polyphenols in green tea may help maintain the parts of the brain that regulate learning and memory. However, repeatedly drinking hot beverages may boost the risk of esophageal cancer.
(Dr Senapati is Professor and HOD Chemistry, Trident Academy of Technology, Bhubaneswar-751024, E Mail: email@example.com)