Tea, the most widely consumed beverage aside from water is grown in about 30 countries but is consumed worldwide, although at significantly altering levels. Tea is fundamentally produced in three basic forms. Green tea is prepared following such a technique as to rule out the oxidation of green leaf polyphenols, but at the time of black tea production oxidation is promoted so that most polyphenols are oxidized. However, oolong tea is a partially oxidized product. Out of 2.5 million metric tons of dried tea produced every year, only 20% is green tea and less than 2% is oolong tea.
Tea and those times
I say let the world go to hell, but I should always have my tea.
Fyodor Dostoyevsky
According to some Chinese legends, tea was invented accidentally by the Chinese Emperor Shen Nong when leaves of the Camellia Sinensis plant drifted into a heated open pot of water. In 59 B.C., Wang Bao wrote the first known book with instructions on buying and preparing tea. In 22 C.E., famed physician and surgeon Hua Tuo wrote Shin Lun in which he described tea’s ability to improve mental functions. Around 450 C.E., the demand for tea rose steadily. Rather than harvest leaves from wild tress, farmers began to develop ways to cultivate tea. In 479 C.E., during the Tang Dynasty, powered tea was produced. Caravans carried tea on the Silk Road, trading with India, Turkey and Russia. In 780 C.E. poet Lu yu wrote the first book of tea describing the methods of cultivation and preparation of tea.
Chemicals responsible for Tea Flavour
Polyphenols, amino acids, methylxanthines and many volatile organic compounds are chiefly responsible for the flavour, taste and aroma. Interesting feature is that in the fresh leaves, most of these aromatic compounds do not exist. However, they are derived from other substances during processing, such as leaf withering, fermentation, and drying. Polyphenols and flavonoids make up 39% of the dry weight of fresh tea leaves. These are important metabolites produced by the plant itself as a defence against predators. Tea is often said to contain more caffeine than coffee. However, this information is based on percentage weight and tea is often diluted much more than coffee. Variety of tea used and brewing methodology can affect how much caffeine is actually extracted into the final drink.
Chemicals responsible for the medicinal properties of Tea
Since ancient times, tea has been considered to possess medicinal properties. It was early in 19th century, when western chemists isolated and characterized the chemical constituents of tea and started synthesising those compounds. Xanthine derivatives such as caffeine, theophylline, theobromine and the glutamide derivative theanine are the fundamental constituents of tea. Such compounds are extremely precious owing to their distinguished stimulant properties, and have also been reported to have beneficial effects on memory and on the immune system. Vitamin E, vitamin C, fluoride and potassium are the other nutritional counterparts of tea.
