In the countries that practice tea cultivation, the upper leaf bud and the next two leaves, the youngest one of a spout is plucked. Older leaves than these tend to have a more negative effect on the quality of the finished tea.
As expected, in the cooler regions higher up, the tea grows slower. This helps the fine and automatic character to develop. The more the harvesting time taken, the better is the quality of the tea. Tea plucking needs a large amount of care as well as skill and this is the reason why it is often done by women. The average plucking capacity amounts to approximately 16-24 kg of green leaves per day. This 16-24 kg of green leaves per day yields 4-6 kg of finished tea.
After this, the green leaves are transported to the factory on the plantation. The green, fresh leaves are still entirely neutral in scent and first have to be treated in the tea factory, passing through various production steps, in order to create an aromatic tea.
The fresh leaves are weighed and the amount is registered when they reach the factory. Now, the withering process starts where the humidity content of the leaves is reduced by 30% in order to make them soft and flexible for the subsequent rolling.
The withering takes place in special withering throughs of a length of 25 – 30 m, which are strung with a wire grid and ventilated with large fans. The leaves are spread out on the grid. The air, which moves through the ventilators, can also be heated if required due to the higher humidity content of the leaves. The withering process takes 12 – 18 hours.
After the withering process, the green leaves are rolled in large rolling machines. These generally consist of two large, heavy metal plates, which are rotating against each other and are hereby breaking open the cells, bringing the cell fluid into contact with the oxygen in the air.
This includes the fermentation as well as the development of the essential oils, which determines the scent and the flavor of the teas. The rolled tea, which now already starts to ferment, is brought into the fermentation room. A “rotor vane” machine is used by some tea factories, which further processes the leaves. Here, the leaves are moved across a slowly rotating screw conveyor through a cylinder into which oxygen is introduced in order to accelerate the fermentation.
The fermentation is an oxidation and tanning process of the cell fluids, which have been released during the rolling. For the fermentation, the leaves are spread out on tables in layers of 10 cm. In modern factories, spraying water from rotating ventilators humidifies the room in which the fermentation takes place
During the fermentation – which takes 2 – 3 hours – the leaves change their color, which gradually becomes a copper-red. This color is found again in wet tea leaves of the infusion. The “tea maker” needs to constantly monitor the degree of oxidation, particularly with respect to the scent of the wet leaves. The quality of the finished tea is very much dependent on the correct fermentation.
When the desired grade of fermentation is reached, the fermentation is finished. For this drying purpose, tiered dryers are used which have to be fuelled with wood or oil. The tea is moved through the dryer on a conveyor belt. The starting temperature amounts to 90°C and binds the cell fluid firmly to the leaves.
Towards the end of the 20-minute long drying process, the temperature decreases to 40°C and the humidity content to approximately 6%. Later, when the tea is infused, the cell fluid, which stuck to the dried leaves, is solved in the hot water and produces the aromatic and invigorating drink.
The black tea is now sieved using some shaking, mechanical sieves that are of varying sieve sizes with which the common leaf grades are separated from each other.
Tea is a product that is made to be durable by reducing its humidity content. Tea should be stored in a cool and dry place. The tea retains its original taste when kept in a tightly-closed container, away from strongly smelling foodstuff such as spices.
Green Tea Production
Green Tea is different from black tea in the sense that it is not fermented i.e. it is not altered by oxidation. The production process is generally the same until after the withering.
During the green tea production, the tea tannins and enzymes are destroyed through the process of steam treatment or roasting after the withering, before the rolling starts – the tea is “steamed” or “pan-fried” and then rolled and dried. This ensures that the leaves are not colored copper-red like the black tea leaves, but remain olive-green.
The infusion varies depending on the variety, cultivation area and plucking period and can be anything from light yellow to dark green.
CTC stands for: Crushing – Tearing – Curling
The CTC production starts by withering the green leaves, after which the green leaves are rolled before they are torn in the CTC machine in between thorned rollers. This ensures that the cells are broken up more thoroughly and quickly than in case using the orthodox tea production. CTC tea is of a more intensive color and is higher yielding. The stems and leaf ribs are extracted to a large extent and only the cut “flesh” of the green leaves is processed further. Afterward, the tea is brought into the fermentation room. Depending on the desired leaf size, this process is repeated several times.
During the CTC-Production, mainly fanning is produced, with no leaf teas and only very few broken teas. Therefore, CTC teas are very suitable for tea bags. Nowadays, tea in India is already produced to 50% and tea in Kenya almost to 100% using the CTC method. In Darjeeling, however, only orthodox tea is produced.