Tea is one of the oldest drinks (used for almost 50 centuries in Asia) and – after water – the most common beverage people enjoy the world over (Mandel et al. 2008). Native to China, it comes from the evergreen plantCamellia sinensis. A cup of tea contains numerous compounds in varying quantities: vitamins, polyphenols, caffeine, fluoride, sugars, amino acids, proteins, minerals, chlorophyll and others (Zhao et al. 2013). Which tea is produced (white, green, oolong or black) depends on the subsequent processing of harvested Camellia leaves. Teas can be classified as non-fermented (green and white teas), semi-fermented (oolong tea), and fermented (black tea).
The health promoting effects of green tea are attributed to the rich antioxidant polyphenol content of its leaves (flavonols & catechins), making up c. 30% dry weight of a tea leaf, and exhibiting biochemical and pharmacological activities (Siddiqui et al. 2006). Recently, many of these beneficial effects were traced back to the most abundant catechin, EGCG (Wolfram 2007).
White tea differs from green tea by only using buds or first leaves. Green tea is rich in catechins. Black tea contains high levels of bisflavanol, theaflavin, and thearubigin, whereas white tea possesses large amounts of epigallocatechin-3-gallate or EGCG, epicatechin, and methylxanthine (Zhao et al. 2013).
And just like a good wine, geographic location, soil and growing conditions play a role in tea quality, too. Tea leaves are heated and dried to inactivate enzymes, thus preserving constituents until we come along to make a brew by simply adding hot water.