riccaicedo wrote:Sorry for the late post, but no one gave a definite answer.
It's due to caffeine. The more you steep, the more caffeine you extract, same thing happens with temperature.
riccaicedo wrote:Then how do you explain the low bitterness of houjicha and kukicha (which are low in caffeine) even if brewed at high temps, long brewing time?
Caffeine isn't the only chemical in the world that has a bitter flavor but in tea it's the major one.
Catechins are the main agent for astringency as well, so perhaps high astringency may increase the sense of bitterness?
riccaicedo wrote:Maybe it's not caffeine alone, but according to this link:
Which has an experiment from a chemistry professor, says that "In fact, it would take a six-minute infusion to remove 80% of the caffeine".
Hence caffeine still plays a role even after a long steeping time.
Why is gyokuro brewed at lower temperatures? To avoid the caffeine (bitter taste) that extracts more efficiently at high temperature while enjoying the mild sweet taste (L-theanine and other amino acids).
I'm also guessing that if you concentrate any tea (by greatly over steeping) we may perceive it as bitter too, aided by the high astringency of catechins.
AlexZorach wrote:Unless I up the temperature or greatly up the steeping time with each progressive steeping (both of which I sometimes do) I find it gets less bitter. I've found this true of all kinds of tea.
Perhaps you brewed the first one too hot?
riccaicedo wrote:I did more research today and it definitely seems that caffeine and catechin play a role in the bitterness.
I would post the links but I'm not allowed yet, I should have read the forum rules before
Another interesting thing I found, but which is more complicated to discuss, is that people perceive bitterness in a different way than just because of concentration of certain bitter compounds. Other non bitter compounds can heighten or lower the perceived bitterness.