Tea - food

Tea is a drink made from the leaves and buds and is the most important non-alcoholic beverage in the world. It has two basic forms: black tea and green tea.

Black tea makes up about 78% of the commercial tea drunk throughout the world, including the famous British 'cuppa' and that most often enjoyed in the rest of Europe and North America. Green tea remains more popular in the Far East.

Black tea

A photograph of Flower pekoe tea from Kew's Economic Botany Collection.
Flowery pekoe tea is made from buds and leaves.

India, Pakistan and Sri Lanka produce mainly black tea which requires very specific production methods. The leaves are 'withered' by placing in special troughs where air is blown through them reducing water content and causing enzyme activity.

The leaves are then rolled, passing through machinery which ruptures the cells and releases enzymes, causing chemical oxidation of the phenolic compounds present. Then the leaves are spread out in a warm, damp atmosphere and left for 2-6 hours to ferment, where they absorb oxygen and become a bright reddish coppery colour. Finally the leaves are dried with hot air to stop fermentation and remove excess water. During this the leaves acquire the characteristic red-orange colour of black tea.

The leaves are then cleaned and sorted into various grades. Some well-known grades of black tea include Orange Pekoe, the Darjeeling teas and Lapsang Souchong. This tea originally acquired its distinctive flavour from the smoke from burning rope that was placed beneath trays of leaves to quicken the drying process.

Teas vary according to which estate they come from and the season in which they were picked. Highly skilled blenders aim to produce a final product with uniform character so that the consumer gets a similar product in every packet purchased. Small pieces of leaves - debris from the processing of whole and broken leaves - are called 'dust' and even smaller ones called 'fannings'. These go into teabags and brick tea.

About half of all tea grown is consumed domestically, and the rest is sold internationally. The British are the world's biggest tea drinkers, getting through some 70 billion cups each year, followed by Ireland. In Britain, 93% of all the tea drunk is made from tea bags. In 1970 this figure was only 2%.

Green tea

Green, or China, tea is unfermented and unwithered. The freshly picked leaves are steamed and dried giving a pale-coloured, delicately flavoured tea. As its name suggests, this tea is grown mainly in China, in the southern and eastern parts of the country, and in Taiwan.

Stimulating and flavoursome

The stimulating effect of tea is due to the caffeine contained in the leaves, whilst the brown colour comes from the tannins present. In order to qualify as tea, in its proper sense, the young shoots must contain a definable spectrum of six catechins and the enzyme polyphenol oxidase. The flavour is a product of the fermentation process and the tea's essential oils. Some teas, like Earl Grey, are flavoured using bergamont orange oil.

The plant has also been eaten raw, cooked or pickled and has even been snuffed.