by tasters and etween 4.5.2 Green tea The inactivation of leaf enzymes as soon as possible after picking, that flavour and aroma is almost entirely derived from com- pounds present in the green leaf, or compounds formed during firing. Further, the strength of both flavour and aroma markedl less than that of black or semi fermented tea. (a) Flavour Three major components of green tea flavour have been identified, astringency, bitterness and brothy flavour. Polyphenols, predomi- nantly catechins(see pages 174-7) are responsible for ca. 75% of astringency and bitterness. Caffeine also contributes to bitterness by complex formation with catechins. The brothy flavour of green tea is associated with leaf amino acids. As many as 18 amino acids may be involved in determining the flavour, but theanine(Ns ethyi glutamine), which accounts for ca. 40-7o% of the total amino acid content of fresh tea leaves is dominant.