Withering

 Withering

Withering is the first process carried out within the factory on the plucked tea leaves. The fresh plucked leaves after sorting are placed on the withering troughs and air is allowed to pass over the leaves. The air fans which are used in this process are called ‘withering fans’. The process of wither aims at partial removal of moisture from the fresh leaf. It is carried out in order to condition the leaf physically for subsequent processing. Besides, some chemical changes also take place during withering and these are independent of the physical process. The process of withering involves:

Physical Wither

During physical wither the leaf loses its moisture and hence turgidity which makes the leaves flaccid or rubbery, a most desirable condition to help in its rolling and for obtaining the desired style and appearance. The extent to which the wither is to be carried out will depend upon the method of manufacture. Under the North East Indian conditions the norms usually adopted are given in Table 3.1(The Planter’s Handbook, TRA)

wither

Chemical Wither

Chemical wither starts immediately after leaf is detached from the plant. It is independent of the rate of loss of moisture and is the function of time and temperature. Following chemical changes occur within the leaf cells.(Khanna, A.I.N. 1999 & Gogoi, M.N., 1999)

  1. Breakdown of larger molecules to smaller ones that results in the increase of contents of amino acids and flavor compound.
  2. Increase in caffeine which is responsible for the stimulant effect of tea.
  3. Increase in permeability of cell membranes which has a great effect on the mixing of polyphenols, enzymes and oxygen for even fermentation.

Green Leaf Processing

Green leaf processing is that step in the process of tea manufacture where the withered leaf is subjected to some kind of mechanical operation whereby the leaf cells are ruptured to give the desired style and appearance to the made tea. During this operation the leaf undergoes the process of size reduction with a degree of cell disruption to allow the exposure of new surfaces to air during the fermentation process. Fig  shows the processes involved in black tea manufacturing (both Orthodox and CTC).