The first step in production of most teas is withering. It involves letting the fresh leaves wither for some period of time after plucking to reduce moisture content.
Tea leaves are an organic ingredient containing moisture. If left alone, the tea would rot, or become moldy, making it useless. To make the tea leaves into viable tea, the leaves must be dehydrated, quickly and safely. In some plantations, the tea leaves are spread out to be dehydrated by the sun, for natural dehydration or withering.
In commercial production, the leaves are placed on dehydrating beds where dry air and low heat cause the moisture in the leaves to evaporate.
As the leaves dehydrate, they begin to curl and wither. As the leaves wither, they become ‘limp’ as moisture is replaced with oxygen and the oxidation of the leaves takes place. Some suggest withering is part of a commercial process, but it’s really an ancient technique to prevent the leaves from natural decay of the organic compounds within them.
Temperature and humidity affect the withering process which is the reason why commercial withering is somewhat better than the natural method as it allows the commercial plant to control these mechanically. The result is a consistent tea product. Natural is preferable to any chemical process, which can also be used, though it is subject to the condition of the air and climate. Too hot (over 35 degrees C. or 95 degrees F.) can destroy the leaves. Too cold (less than 20 degrees C. or 68 degrees F.) and the process can slow down within the leaves and subject them to rotting or mold infestation.
The leaves must be turned and moved periodically to ensure that moisture, affected by gravity does not settle and cause rotting. In commercial withering, heat is often applied, along with movement of the leaves to ensure the best possible conditions for the leaves.