Tannins
Tannins are polyphenolic compounds (having OH on aromatic ring…) with molecular
weights of 50-20,000. Tea tannins are soluble in water and therefore extracted from the
leaf and responsible for the typical bitter taste of tea. Tea tannins belong to a subgroup
named hydrolysable tannins. The core structure is D-glucose, to which several units of
gallic acid are attached, via ester bonds. (Figure 3) It is important to note the gallic acid is
poly functional, and able to form multiple ester bonds