ABSTRACT
Tea (Camellia sinensis (L.) O Kuntze) is an important crop that is grown in a number of countries. The beverage produced from its processed leaves is consumed across the world because of its special flavour and stimulating effect on the human body. Global tea production has increased by 4.2% annually over the last decade and was around 5.13 billion tons in 2014 (Chang, 2015). This popular drink is prepared by extracting the mostly non-fermented (green tea), fermented (black tea) and semi-fermented (oolong tea) leaves of the tea plant by adding hot water. A cup of tea tastes good when the soluble substances present in the dry tea leaves come into the liquor in the right proportions. For this reason, many scientists across the world are interested in working more intensely with tea quality and, consequently, the factors that enhance quality are well known. Fresh tea shoots are extremely rich in polyphenolic compounds, the largest group being the catechins (flavan-3-ols), which constitute 30-35% of the dry weight of the material (Engelhardt, 2010; Harbowy and Balentine, 1997; Robertson, 1992). They are present as ‘catechins’ in fresh tea leaves or in green tea. In black tea, catechins undergo fermentation to yield oxidation products such as theaflavins (TF) and thearubigins (TR). These oxidation products of polyphenols are responsible for the colour, flavour, taste, briskness and overall
strength of tea liquor. TF have several beneficial health effects, including antioxidant activities (Almajano et al., 2008; Dufresne and Farnworth, 2001; Ganguly, 1995; Gardner et al., 2007; O’Coinceanaima et al., 2004; Shibasaki and Kitakawa, 2003). Apart from caffeine, tea also contains a unique amino acid, theanine, which is found only in tea plants. Theanine makes up to 50% of all amino acids and is reported to have health benefits as well (Ekborgott et al., 1997; Engelhardt, 2010; Haskell et al., 2008).
