Dog Ma /28/03
reply w/o spam

> I may regret this, but flame-proof suit is well-zipped...
>
> On the temperature front, I'd say that whatever works for you is right. It
> IS true that for the great majority of serious sippers, black teas taste
> best if brewed at the highest possible temperature. That usually means fully
> boiling water and a hot pot, even at sea level - never had really good black
> tea at altitude, where boiling temp is reduced. I've even done the
> experiment of maintaining a boil in the microwave, and gotten better tea.
> Issue here is not to distill away delicate aromatics. (As a side-point,
> little aroma will be lost in normal brewing no matter how hot the water -
> has to do with partial vapor pressures of soluble volatiles in a very dilute
> solution.)
>
> Green teas tend to get very bitter if overwarmed. Much of the unpleasant
> bitter stuff is rapidly soluble; hence the pre-rinse favored in some
> techniques. Note that brewing time and temperature are not interchangeable:
> a fast brew at boiling does not produce the same result as a longer steep at
> 80C. In Asia, unlike the US, many people seem to make a practice of multiple
> extractions from the same green leaves. Even with a fast pre-rinse in hot
> water, I find the second and third steeps to make a much nicer tea than the
> first; the fourth is pleasant but weak.
>
> Tea brewing chemistry is not extremely complicated, but there's a lot of
> mythology. The "oxygen" thing is simply not true - not much there under any
> circumstances, and nil effect in the brew. What is true is that lime-rich
> water (which, IMO, makes the best tea) loses CO2 on boiling. This reduces
> the solubility of divalent (calcium and magnesium) salts, so they crust up
> in the kettle and leave less alkaline water - which then does a worse job of
> extracting slightly acidic polyphenols and other good things. (Alkaloids
> like theophylline are so soluble that none of this much matters, only full
> hydration of the leaf.) So a fresh boil of freshly drawn water is important
> IF you're fortunate to have slightly hard water. Where it's very pure, as in
> much of the northern UK, it makes little or no difference.
>
> There's also some interesting stuff that happens later. For example, some of
> the tannins bind (not actually reacting) with the alkaloids, settling out in
> a fine floc and shifting flavor. This is one key reason why length of both
> steeping and standing matter: alkaloids are extracted very rapidly, tannins
> more gradually; and that flocculation takes a while too. The protein in even
> a minute amount of milk - not nearly enough to taste milky - has a similar
> effect.
>
> One could go on. There's some very good research on tea available on the
> web, differing markedly from common mythology. I have a Ph.D. in organic
> chemistry, have read a number of scholarly treatises on tea technology and
> even worked a bit in the field - and I'd still say: forget all the stories,
> start with what old-timers recommend, vary everything and make careful
> observations. Then do the easiest (or most fun) thing that works for you.
>
> -DM
>
>


No need for the flame-proof suit, Dog. Your post is interesting, and your
points are well taken, especially those in your last paragraph. Ultimately,
tea must be more art than science.

Michael