Abstract
Green tea made from high amino acid content (HAAC) tea cultivars with different leaf colors exhibits many similar characteristics, such as slight bitterness, a rich aroma, and a refreshing and velvety taste. To determine differences in the key constituents of five HAAC tea cultivars with various leaf colors, the cultivars quality constituents were systematically analyzed and compared with that of a normal green tea cultivar. High theanine (Thea) content and the synthesis of Thea precursors are extremely important determinants of the character of these HAAC tea cultivars. The levels of most catechins, carotenoids, and chlorophylls in the HAAC tea cultivars were significantly lower than those in the normal tea cultivar, as was that of caffeine. The present study suggests that the inhibition of catechins (particularly epicatechins; ECs), chlorophylls, carotenoids, and caffeine biosyntheses in HAAC tea cultivars directs the metabolic network toward amino acid biosynthesis, particularly Thea biosynthesis.
Highlights
Tea is one of the most widely consumed nonalcoholic beverages worldwide because its water-soluble components have important health benefits (Khan and Mukhtar, 2013; Fang et al, 2014)
Differences in the free amino acid content in high amino acid content (HAAC) tea cultivars In total, 19 amino acids were detected in the shoots of all HAAC tea cultivars, and these were compared with those detected in the normal green leaf tea cultivar Jinming 1 (JM1) (Table)
The present results indicate that the higher Gln content was due to inhibition of chlorophyll biosynthesis in the three albino mutant tea leaves, whereas lower Gln content was due to the activation of Thea biosynthesis in the two normal green leaf HAAC tea cultivars
Summary
Tea is one of the most widely consumed nonalcoholic beverages worldwide because its water-soluble components have important health benefits (Khan and Mukhtar, 2013; Fang et al, 2014). The quality of processed tea is mainly determined by its metabolic constituents such as free amino acids, catechins, purine alkaloids (caffeine), and pigment (chlorophylls and carotenoids) (Cabrera et al, 2006; Li et al, 2016). Among these constituents, free amino acids have been reported to be the primary contributors to the taste of green tea and are the main constituent of the thearubigin fraction, which is responsible for much of the color of the black tea brew (Yamaguchi and Ninomiya, 2000; Chen and Zhou, 2005). The breeding of tea cultivars with HAAC ( Thea content) is crucial to enhancing the quality and health functions of tea
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