What is Tea?on Sep 16, 2019
As the second most commonly drunk beverage in the world (after water), most of us are very familiar with tea, but there might just be more to your humble cuppa than you think.Real tea is an infusion made from steeping the processed leaves of the tea plant with water. The tea plant, Camellia sinensis, is an evergreen plant that thrives in the tropics but, like wine, produces exemplary results when grown at extremes, such as at high altitude in Taiwan or Darjeeling or on precipitous slopes.
Herbal teas, on the other hand, are infusions made by steeping almost anything other than real tea with water, eg dried herbs, petals, flowers, bark and seeds. These beverages, correctly known as tisanes, are often caffeine free and quite uncomplicated.
In contrast, real teas can be quite complex due to the processing steps that convert the abundant chemical compounds in the raw leaves into an array of desirable aromas and flavours in the finished leaf. It is these chemicals, such as polyphenols, amino acids, chlorophyll, minerals and volatiles, which have led to the association of tea with good health and a proliferation of scientific studies on the subject.
There are two main varieties of the tea plant – Camellia sinensis sinensis (meaning from China) and the larger-leafed Camellia sinensis assamica( originally from Assam) – and there are thousands of cultivars, or varietals, of each variety. The final character of the tea will depend on the particular cultivar used but also on a range of other factors. These include the way the leaves are cultivated, picked and then processed, as well as the terroir of the growing area. Terroir is a term borrowed from the production of wine and refers to the natural environment where the tea is made, including soil, climate, altitude and latitude, all of which impact on the individual character of the finished tea.
Theoretically, after the tea leaves have been picked, they could be processed into any one of the 6 main tea categories: green, white, yellow, oolong, black and dark. In truth, however, some cultivars are much better suited to different styles than others, but is it customary to define the tea category depending on how the leaves are processed after picking.
The main tea processing steps are withering, oxidation, drying and sorting. Not all teas go through the full gamut of processing steps and, to make life easier perhaps, it is the level of oxidation that is most often used to distinguish between tea categories. For example, after plucking, leaves for green teas are heated immediately to halt oxidation, preserving the green colour of the raw leaves, and, at the other extreme, leaves for black tea are fully oxidised. Oolongs are partially oxidised teas and the leaves for white tea experience a light natural oxidation that is neither encouraged nor prevented. Unlike in the other tea categories, dark teas such as puerh are fermented and have the ability to continue to improve with time.
So, in all, it’s fair to say there is a lot to learn about tea! Tea chemistry is complex and much of it is still not understood. However, and partly thanks to the link with tea and health, there is now more research worldwide than ever before on the subject, and the secrets of the very special tea plant are being slowly unravelled.