To manufacture black tea, the freshly picked leaves are first withered in troughs or on baskets to allow some of the water in the leaf cells to evaporate. Once the leaves have started to dry a little, they are rolled or cut to break the cells and expose the juices inside the leaf to oxygen in the air. The reaction between the leaves’ juices and oxygen is called ‘oxidation’ and is similar to what happens to the flesh of a pear or an apple when the fruit is cut open. As the tea eaves oxidise, the leaves change from green to brown and develop a warm, fruity smell. Once the leaves have all turned to rich brown, the tea is passed through hot ovens to stop oxidation and to remove all but 2-3% of the remaining water content. Black teas are fully oxidized.
In order to capture the green colour and character of freshly harvested tea leaves, heat is applied quickly to the tea to stop any natural oxidation. This can either be dry heat applied in a wok or inside the rotating hot drum of a panning machine, or steam that is passed through the leaves inside a steaming tunnel or chamber. Once this part of the process has taken place the leaves will not oxidise but can be rolled or pressed to develop the flavour inside the leaves without losing the delicious fresh aroma and flavor of young spring vegetables and freshly-mown grass. Finally the tea is dried to remove all but 2-3% or the leaves’ water content. Green teas are not oxidized at all.
White tea is the least handled and manufactured of all teas and processing simply involves careful plucking and drying. It is important not to break the cells of the buds and leaves while they are being removed from the plant, because once the cells have been bruised, the leaves and buds will start to oxidise and white tea should be oxidized as little as possible. What oxidation there is in a white tea is natural and not provoked or arrested by tea manufacturers. In the past in China, young girls with very nimble fingers were sent out into the tea garden with a pair of golden scissors and a golden bowl so that they could just snip off the little buds and catch them in the bowl. Once the buds or baby shoots have been carefully gathered, the tea is laid out in the open air to wither and dry and final drying takes place indoors. The entire process usually takes 2-3 days. White teas that are made with just the bud are called Yin Zhen or Silver needle and when a baby shoot of one bud and one of two small leaves are gathered, the tea is called Bai Mu Dan or White Peony. White teas undergo very light natural oxidation.
Oolong (Black Dagon) teas are partially oxidised and therefore fall between unoxidised green etas and fully oxidized black teas. The oxidation in oolong teas can be on a sliding scale between approximately 20% and 60-70%. The longer oxidation takes place in the leaves, the darker in colour the laves will become and the darker the brew in the cup will be. To make oolongs, the freshly picked leaves are withered in the sun for about two hours and then further withered indoors where the tea manufacturer bruises the leaves lightly and tumbles them in a bamboo drum in order to provoke light oxidation. Wherever the cells of the leaves are broken or bruised, the tea will gently oxidise. Once the required level of oxidation has been reached, the leaves are heated in a wok or a panning machine to stop any further oxidation. Then they are rolled to develop the flavour. The large-leafed darker varieties are then dried, but the greener, very popular balled oolongs (often referred to as Jade Oolongs) before being dried go through further stages of processing during which the leaves are repeatedly wrapped in cloth bags and rolled until the leaves or shoots have become tight little pellets. Oolong teas are referred to as semi-oxidised or partially oxidized teas.
Rooibos is a caffeine-free herb that is loved for its soothing properties. The plants grow in profusion in the Cederberg Mountains of South Africa and once a year, as the bush is ripening in the hot summer sun, large bundles of the very fibrous, woody stems and leaves are cut off with scythes and taken to the factory. Here, they are chopped up, spread out in a vast courtyard, dampened with water and left to oxidise to a rich rusty red colour. The small needle-like particles are then allowed to dry in the sun before being scooped up and taken indoors for cleaning, sorting and packing. In South Africa, Rooibos is used to make Red Espresso, Red Cappuccino, and it is also popular in lattes and frappes.
Caffeine in tea
All tea contains caffeine. Caffeine is in the plant as it grows and there is a concentration in the new buds where it acts as an insecticide to fend off attacks from bugs and other pests. The caffeine level is not affected by manufacturing processes and so all types of tea contain more or less the same amounts. But the temperature of the water used for brewing and the length of time the tea leaves are infused does make a difference to the amount of caffeine in the cup or mug. The hotter the water and the longer the brewing time, the more caffeine there will be in the tea; and vice versa, the cooler the water and the shorter the brewing time, the less caffeine there will be in the tea.
Herbal and Fruit Infusions
Most herbs, fruits and flowers contain no caffeine and so make wonderful alternative brews for those wish for a decaffeinated infusion. Often called ‘tisanes’, each particular herbal, flower or fruit infusions has its own individual health benefits, but those health-giving properties are different from the benefits of drinking tea. Peppermint and other members of the mint family are good for the digestion; chamomile is soothing and calming; lemon and ginger helps settle the stomach and boost immunity; rosehips are full of vitamin C and help fight infections; and fruity blends make deliciously sweet drinks which are wonderful either hot or poured over iced.