ABSTRACT
Tea is one of the three major non-alcoholic beverages in the world. Tea plant has been cultivated for several thousand years in China. The tea plant Camellia sinensis or Camellia assamica is believed to originate in the mountainous region of southwestern China as many species and endogenously wild tea trees have been discovered in primitive forests in Yunnan province (Yu and Lin, 1987). The words te, qia or cha denote tea in various Chinese dialects, and in one or other of these forms has been transposed into other languages. At the very beginning, leaves from wild tea plants in forests were picked and steeped in boiling water and the brew was drunk. During the second and third century AD, tea leaves were pressed into cakes with rice gruel and then dried. The dried tea cake was then ground for brewing. From the 10th to 14th centuries, the Chinese adopted the pan-firing method to process green tea. At the end of the 14th century, dark green tea came into being. This was followed by the development of processing for production of Oolong tea, white tea, black tea, and scented tea. Classification of made tea is based on the degree of fermentation and oxidization of polyphenols in fresh tea leaves. Up to now, there are six types of teas: green, black, Oolong, dark green, white, and yellow tea. Green, yellow and dark green tea are non-fermented tea as polyphenols in fresh leaves are less oxidized, green tea belongs to absolutely non-fermented tea; however, polyphenols in yellow and dark green tea are non-enzymatically oxidized during the processing period. White tea, Oolong tea and black tea are fermented teas, while green tea is non-fermentation and black tea the most fermentation, thus, Oolong tea is also called semi-fermented tea. Each kind of tea has its characteristic flavor and appearance. Besides the above six teas, flower scented tea, compressed tea, instant tea and herbal teas are classified as reprocessed teas. In this chapter, special emphasis will be placed on the classification, manufacture, processing biochemistry and factors affecting the quality of these teas.
