You know Guy I could be wrong. I totally agree that learning your system is key. Good beer can be mad by the most primitive brewing system as long as the brewer knows how to run it. I feel like this is not the thread for the tannin part of the discussion and I probably should not have brought it up as it always gets things going.
Here is a piece of a conversation from HBD about tannin extraction. It took place about a year and a half ago and the author singed as -S. Until this conversation I also believed that pH drove tannin extraction to some extent. Now I understand it is likely the other way around.
It's well known that when using neutral sparge water the late runnings
have a rise in pH and at the same time phenolics and other less
desirable extract increases (as a percentage of extract) in the
runnings. The pH rise is explained by the loss of organic acids in
malt. The extraction of phenolics, cellulose and other less desirable
components is attributed to extensive malt cell membrane disruption.
There is NO EVIDENCE I've ever seen that keeping the sparge water
pH low prevents phenolic extraction. This correlation of phenolic
extraction & pH rise at same time does NOT imply that this slightly
lower pH *causes* phenolic extraction. It may, I can see some
hypothetical arguments to support the notion, but don't wager your
batch on this. We should consider the idea that low pH sparge water
prevents phenolic extraction as questionable,
take-with-a-grain-of-salt. Also very low or very high pH will cause
release of specific phenolic fractions. You are probably safe (wrt to
phenolics) using any sparge water pH between mash pH (say 5.3) and the
natural pH of the grain (~7.5); lower is certainly not better.
Alkaline water will increase the wort pH and that's not good for break
formation or for fermentation. *Do* remove carbonate buffering in
sparge water with acid, but the idea that lower pH prevents astringent
sparge is possibly just homebrew-voodoo, a sub-urban brewery legend.
Cheers,
-J
