Producing tea is all about oxidation. White tea has little or no oxidation and Black tea has a lot of oxidation of the tea leaves. In the middle we have yellow and green tea. The provenance of the tea will effect flavour but also the processing....
White Tea:
Hardly
any processing and no heat. White tea differs principally from green
teas in that the white tea process does not incorporate any steaming
or pan-firing. The name comes from the silver needle white teas that
are used to produce the leaves. The tea plant is called "chaicha".
The leaves are thinner and smaller and have a silvery-white down.
The
flavour is described, typically as delicate with a lingering floral
fragrance and a fresh, mellow, sweet taste with no astringency and
grassy flavours.
Yellow
Tea:
Yellow
tea is partially oxidised tea leaves with some mild steaming
involved. During the processing the chlorophyll is broken down and
partly oxidized. The taste of yellow tea is somewhat milder, and
described as being somewhere between white tea and green tea. The
aroma is described as flowery and fresh.
Green
Tea:
Tea
is first plucked from the stem, two leaves and a bud.
the leaves
are then cleaned and dried and often steamed for less than one minute
in large vats. This is kills enzymes that may initiate or cause
oxidation.
The leaves are then kneaded by hand, piled and dried for
about ten hours during which time it is constantly turned.
The
leaves are then pan fired and this stops the oxidation process for good.
Typical flavour descriptors include: sweet, bittersweet, nutty,
vegetal, buttery, floral and fruity.
Black Tea:
The
final black tea that we buy is a highly oxidised product. The
polyphenolics that were green have effectively been oxidised (like
Iron and rust!) and are now darker and often a black/brown colour.
There
is a critical withering part of the process where the leaves
withered and rolled this process bruises the leaves and lets the
chemicals in the leaves mix which initiates the oxidation process .
The leaves are then separated by a roll breaker to allow for the full
oxidation of the tea leaves. This process goes on for several hours
while the leaves are spread out in a cool place. Drying / Pan Firing
then stops the process. The leaves can then be sized, sorted and
blended accordingly. Taste profiles of black tea are varied but
really are an extension of the green tea flavour with more astringent
and cooked notes reflecting the extra oxidation.