Fermentation of black teagreen tea By: Sajida!
Black tea • The processing of black tea is done in four main steps: • 1. Withering • 2. Rolling • 3. Fermentation • 4. Drying
Withering • Leaves lose moisture • Physical withering • Chemical withering
withering • under the sun. • spreading the flush very thinly on the mats or in thick layers in troughs
rolling • To mix up the enzymes with substrates • Done by CTC (crushing, tearing and curling) machines. • Rolling ruptures the cell wall
fermentation • exposure to warm air makes it fermented • tea acquires its flavor, quality and strength and color • The period may vary from twenty minutes to five hours. • leaf changes from greenish to a bright coppery color.
fermentation • Further fermentation is prevented to take place. • Duration of fermentation is important, for quality of tea. • Fungus may contaminate the tea with toxic and carcinogenic substances
Drying • Reduces the moisture content leaves from 45-50% level to a 3% level • Develops black tea aroma. • Drying is physically achieved by blowing hot air through fermented leaves • The drying process lasts for about 20 minutes.
Oolong tea • Semi-fermented • 15-65% oxidized • Processing • Withered • Rolled • Fermented • Dried
Green tea • The fermentation stage is completely omitted from processing and enzymatic activities by heating • The character of green tea is determined by the endogenous components of the leaves at the time of plucking rather than by compounds formed in post-harvest reaction.
Health potentials • drinking tea is associated with cell mediated immune function in human body. • improves the intestinal micro flora and also provides immunity against intestinal disorders. • Due to presence of fluorine, it also prevents dental caries. • Catechins in green tea possess anticancer properties. • exert anti-obesity, anti-diabetic, and anti-inflammatory effects." catechins that have anti-carcinogenic, anti-mutagenic and anti-tumoric properties.