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Green
teas are unfermented teas. Preparation therefore
aims to avoid any hint of fermentation (oxidation).
Processing is carefully monitored and complex.
Processing generally involves a number of phases
including steaming, cooling, rolling, twisting,
pressing and drying. Steaming for 30 to 90 seconds
is designed to kill any enzymes that might cause
fermentation. Heating is intense but short in
duration ranging from less than one minute to as
much as five minutes.
Steam
sterilization in Japan is ideally undertaken within
two hours of harvesting as the chemical compounds
that contribute to flavour start to alter
immediately after harvest.
Hand
rolling or folding is not economical in Australia
and only types suited to mechanical processing can
be made. In Japan, tea is transferred to a primary
drying tea-roller, a machine that twists and dries
the tea at high temperatures. The leaves are then
transferred to a secondary drying tea-roller, which
further twists and presses the leaves, breaking up
the cells to produce an even distribution of water
content. Lastly, the tealeaves are transferred to a
dryer that reduces the water content to between 5
and 6%.
In Japan, the final product is called
aracha, with a product weight approximately 22% of
the wet weight of fresh tea leaves. This is not the
tea sold to final consumers. Final processing is
still required involving further drying and
carefully controlled packaging and blending of
different batches to give a uniform tea. |
Pilot green tea processor at the Department of
Agriculture and Food Horticultural Research
Institute in Jardee near Manjimup. |
