Technology Trends in Tea Manufacturing
Tea plucked from the garden is sent to the factory for processing, which in most cases, is in or near the tea garden. This processing, earlier, used to depend solely on the natural weather conditions, but to become less dependent on the unpredictable weather conditions which affects productivity adversely, modern technology has been introduced in the tea industry. This has made it possible to increase the plantation area by minimizing space; also labour cost has come down and the entire process has become much more speedy.
The starting material in black tea processing is the young shoot, the terminal bud and the two adjacent leaves plucked from the tea plant. The flush is processed in four distinct stages, which are withering, rolling, fermentation and drying. Each stage involves characteristic changes in the physical and biochemical composition of the leaves and the cumulative effect of these changes are ultimately reflected in the quality of the finished product, namely the black tea. After the drying is over, the leaves are sorted, that is, divided into different grades and made ready for the market.
Plantations :Unlike other perrenials, tea is unique because only its vegetative parts - the two leaves and the bud - are commercially exploited. Tea is also maintained as a low bush in a continuous phase of vegetative growth. Both these aspects call for manipulation of plant parts for optimal productivity and growth
Plucking & Leaf Handling:The plucking of the two leaves and a bud involves a number of systems - Janam plucking, fish-leaf plucking , step-up plucking etc.. Shear plucking is done when there is a scarcity of pluckers during July to September. Pluckers' productivity is found to be maximum in unpruned teas. The plucked leaves are processed to produce the black tea.
Withering : It is a procedure which brings about physical and chemical changes in the shoots to produce quality, apart from conditioning the flush for rolling by reducing turgor, weight and volume. Previously the flush used to be withered under the sun. Now this process is generally achieved either by thinly spreading the flush on mats, or in thick layers in troughs for 8-18 hours depending on the condition of the leaves.
Rolling : The object of rolling is to macerate the leaf so that the enzymes and their substrates get intimately mixed up. This is achieved mechanically either by the use of an orthodox roller, the rotorvane, or by CTC (crushing,tearing and curling) machines. Rolling ruptures the cell wall thereby enabling the production of enzymes.
Fermentation : It is the process of oxidation of leaves. The mechanical aspect involves spreading out of the leaves macerated by rolling a layer 5-8 cms thick, for 45 minutes to 3 hours, depending on the quality of the leaves. Fermenting machines make the process continuous, that is, every unit of macerated leaf has to be spread out for individual treatment.
Drying : It reduces the moisture content of rolled and fermented leaves from 45-50% level to a 3% level in dried black tea. It also allows development of black tea aroma. Drying is physically achieved by blowing hot air through fermented leaves as they are conveyed in chains. The drying process lasts for about 20 minutes.
Sorting : Sorting may be defined as a procedure in which particles of bulk tea are separated into grades of different sizes. This sizing can be done either manually or by using different sizing equipments. Sorting meshes of various sizes are used to grade the tea.
The most common misperception is that the different types of tea come from different tea plants. Black, Green and Oolong teas are all derived from the Camellia sinensis evergreen plant. The difference comes from how the plant is processed.
Black Tea:
The Black tea process goes through the most stages. Once the leaves are picked, they are left to wither for several hours. After the leaves are rolled, oils from the leaves are brought to the surface. These aromatic oils aid in the oxidation process, which last for several hours. The last step consists of placing the leaves in an oven with temperatures reaching up to 200 degrees Fahrenheit. When the leaves are 80 percent dry, the leaves complete their drying over wood fires. The resulting product is brownish (sometimes black) in color and is sorted accordingly to size, the larger grade is considered "leaf grade," and smaller "broken grade" are usually used for tea bags.
Oolong Tea:
Oolong goes through a similar process that black tea goes through. The first two steps are withering and rolling. Instead of rolling, sometimes shaking is done to bruise the outer edges of the leaves. The oxidation period for oolong is half that of black tea. Once the veins become clear and the edges of the leaves become reddish brown, while the center remains green, the oxidation process is stopped by firing. For oolong tea, the leaves are heated at a higher temperature so that they can be kept longer, due to the lower resulting water content.
Green Tea:
The process for making green tea is the shortest. Withering is done first, but this step might be omitted. Rolling the leaves to break the membranes for oxidation is skipped, hence the oxidation process is also skipped. After withering, the leaves are pan fried or fired to prevent oxidation from occurring. The last step is to roll the leaves and dry them one last time for its final shape. The green tea leaves usually remain green.
