Tea, Camellia Sinensis
All the diverse types of tea – including black, green, oolong and white - are derived from just one species of plant, the Camellia sinensis. The colour of tea is determined by the production process, in particular, the level of oxidation that leaves are allowed to undergo.
When plucked, cells in the tea leaves break to some extent during the handling – also, they are in some cases deliberately broken further as part of the manufacturing process. Once the cells break, oxidising enzymes are released and begin to react with the oxygen in the air. Chemical reactions that follow are crucial to the colour and aroma of the tea – which is why this so called oxidisation process is closely monitored by manufacturing experts to ensure the optimal quality and outcomes.
After plucking the tea leaves undergo withering, i.e. they are left to dry so that their moisture levels drop and they become soft and easier to handle. Methods of manufacturing and withering periods vary greatly, however, white teas are generally left to wither the longest whereas green teas do usually not undergo any withering at all.
After withering, the leaves are rolled either by hand or mechanically, to break down the cells and release the oxidising enzymes they contain. At this stage of the process rolling is carried out only for the black teas, to expedite their oxidisation process. Black teas are fully oxidised and their liquor is typically more astringent and full-bodied than other types of teas. Oolong teas undergo a gentler oxidisation process, expedited through stirring of the leaves and stopped at 10-30% or 60-70% level, depending on the type of oolong in question. White and green teas are not deliberately oxidised this way at all.
When the oxidisation has reached the desired levels, the leaves are heated to destroy the heat-sensitive oxidising enzymes. In the case of green teas, the heating is generally done soon after plucking and before rolling, to prevent oxidation altogether. After heating, tea leaves are rolled to their desired shapes, with the exception of white teas that are the least processed of all tea types and not rolled or formed in any way.
Finally, the tea leaves are dried to reduce their water content down to a couple of percentages, to achieve the best balance with good infusion and optimal conservation.
Teas that are not teas
Originally from South Africa, rooibos or redbush tea is growing in popularity also elsewhere in the western world. Rooibos is not just a flavoursome, caffeine-free alternative to the traditional tea made of Camellia sinensis, it is a ‘superplant’ packed with nutrients and active substances with health benefits, ideal also as a beverage for children.
Rooibos is made from the bush-like Rooibos plant and it is processed into two types: the more popular red-brown coloured rooibos that is oxidised during processing, and the light green rooibos that doesn’t undergo oxidisation, and has a grassier taste than its red equivalent.
Maté is widely consumed all over South America, and especially in Argentina, Chili, Paraguay, Uruguay and Southern Brazil. It is made of leaves of yerba maté plant, from a different family of plants than the tea plant Camellia sinensis. Rich in caffeine, maté has a long history of use as a drink to boost energy and focus, and to rejuvenate the body.