Bitter Substances
(= Tannins) Vital component of the tea. Buds and leaf tips contain
less, the rest of the leaf contains more tannic acid. This character is
changed via fermentation. Black tea has a higher content of oxidised tannic acids and less non-oxidised tannic acids than green tea. Due
to its bitter flavour, it is sought to keep the content of non-oxidised
tannic acids as low as possible or even to reduce it.
The tannins
are relevant to the calming effect of tea. They, as well as the
theophyllin which is contained in the tea, act astringent with respect
to the intestine. The theophyllin has a draining effect on the cells.