Plucking leaves off the tea tree is, of course, the first step of harvesting a tea plant.
These freshly picked leaves contain various enzymes that can trigger an oxidation reaction,
called “fermentation,” when properly processed by tea makers.
Different degrees of fermentation yield different tastes and colors of tea liquids.
The liquid of the tea that has never gone through fermentation has a light green color, and as the fermentation process continues, the liquid grows darker and darker, turning from yellow to black.
Separately, non-fermented tea is the closest to the plant flavor with a vegetal scent (e.g. green tea). Light-fermented tea generally has a floral scent (e.g. Dong Ding Oolong Tea or Four Season Tea), while heavy-fermented tea comes with a ripe fruit scent (e.g. Iron Goddess Tea or White Tip Oolong) and complete-fermented tea such as the black tea has a candy scent.
Experienced tea makers can bring out the best of the tea by taking the leaves through just the right amount of fermentation based on the tea type, the area where the tea is grown, and the weather when the leaves are picked.