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Freshly withered leaves. |
The
first step after harvesting leaves from the tea plant, Camellia Sinensis, is to
wither the leaves. Withering is the
reduction of moisture and the softening of the freshly picked leaf. The point of withering is to prepare the tea
leaf for the assault of processing. For
green, oolong, yellow and black teas, the tea leaves will be crushed, pummeled,
rolled and pressed via hand or machine. Why
the assault? To force the juices from
the inner structure of the leaf to the surface to get oxidation going. Oxidation is the chemical change that occurs
when enzymes in the juices react with oxygen in the air of the surrounding
environment. The final tea product is
defined in part by the amount of oxidation achieved in processing. White tea is generally not oxidized; green
tea gets the least amount of oxidation; and oolong and black tea get quite a
bit of oxidation – which equates to more assault for oolong and black tea
leaves.
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Leaves after assault of processing. |
OK,
let’s get technical. There is a physical
and chemical aspect to withering which conditions the leaf for the assault stage
of processing. In the physical aspect of
withering, moisture content is reduced which makes the leaf become soft,
slightly rubbery and flaccid enough to withstand assault without breaking. A “soft” wither retains a higher percentage of
moisture in the leaf, whereas a “hard” wither retains less. In the chemical aspect of withering, large
organic compounds break down into more simple molecules, a natural process that
begins the moment the leaf is plucked. Proteins degrade to amino acids which initiate
aroma compounds. Volatile Flavor
Compounds (VFC) develop and increase in intensity the longer the wither. “Liquors from fresh leaf are bitter, but in well-withered
leaf, sweetness develops.”[1]
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Freshly harvested leaves laid out to wither. Photo credit: Chris Falter |
Withering
time can be expected to range from 12 to 16 hours [2], but
that can vary greatly due to humidity and temperature of the region. Typically the leaves are laid out evenly to
wither at their own natural pace, but sometimes they are helped along by warm
air blown over them, or heated pans under them.
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