22-08-2012, 12:57 PM
Technology Trends in Tea Manufacturing
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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.
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.
Tea Production Process
The Tea Production include of all these process, even for the traditional process is not mentioned about the process order, but actually they do of all these:
Withering Process:
Withering is the first processing step in the factory and is a process in which freshly plucked leaf is conditioned physically, as well as, chemically for subsequent processing stages. Indeed, withering is one of the most important tea processing steps and can be said to constitute the foundation for achieving quality in tea manufacture. Based on achieving the desired level of withering, one can make better quality teas and, on neglect, can invite serious problems in subsequent steps of manufacture.
Leaf Maceration:
The principal objective of leaf maceration is to undertake cell rupture carried out in a rolling machine where progressive disintegration of cellular organelles takes place. The process results in exposure of cell sap leading to intermixing of chemical constituents and enzymes in the presence of atmospheric oxygen to form the important chemical constituents responsible for characteristics of tea.
From the moment the maceration starts, the ‘fermentation’, which is primarily an oxidation process, begins. The shoot with different degree of tenderness is subjected to considerable deformation during rolling, and, during the process of gradual rupture of leaf, theepidermis is torn up in pieces, cells are crumpled, the cuticle wrinkled and the intercellular space is increased.
The mechanical breaking of shoots at this stage also results in the formation of particles of various shapes and sizes depending on the method adopted and the extent of cell damage. These factors have strong effect on the processing steps that would follow as well as market choices for the made teas. Therefore, leaf maceration is also a key step in tea manufacture.
Rolling Process:
Before the advent of tea machinery, the most convenient method for cell rupture was to rub the leaf in between palms. The Rolling table is simple equipment that emulates the hand rolling method in a commercial level operation. The process of rolling applies pressure and twist between leaves as well as between leaf and surface of the equipment used for rolling.
The degree of pressure depends upon the quantity of leaf charged as well as the position of the pressure cap. Resulting friction causes heat, which in excess will hasten the chemical reactions to result in the formation of undesirable constituents detrimental to the quality. The cell rupture in the small and tender shoots is completed faster and chemical reactions set in earlier while the coarser leaves require a little more time. Also the leaf, which has already undergone size reduction and twisting after some amount of rolling, impedes twisting of larger leaf, which may extend the period of rolling.