In addition
to the aroma of these beverages, the high concentration of these psychostimulants
has contributed to the popularity of drinking coffee and tea. Coffee, tea, and cacao
develop their distinctive color, flavor, and aroma during a fermentation process involving
various microorganisms. Most of the teas are produced by a natural oxidation
process without microorganisms; however, there are also microbial fermented teas
like kombucha or puer tea. The fermentation process is of crucial importance for
the quality of all products. Cacao and coffee require a roasting process before they
acquire their full flavors.
13.2 Tea
13.2.1 Green, White, Oolong, and Black Teas
Today tea is the second most popular beverage in the world after water. Tea plants
belong to the Theaceae family and two main varieties exist: Camellia sinensis var.
sinensis and Camellia sinensis var. assamica. The assamica varieties generally have
large leaves, are rich in flavonols and caffeine, contain high polyphenol oxidase activity,
and are best suited for processing black tea, whereas the sinensis varieties have
small leaves, have more nitrogenous compounds than flavanols, have a relatively
low polyphenol oxidase activity, and are suited for processing green tea (Hara et al.
1995b). The first apical leaves are harvested manually or with equipment and are processed
by different methods resulting in the four basic types of tea: black tea, Oolong
tea, green