From the HBD Archive
From: Pete Soper <soper@maxzilla.encore.com>
Subject: extracting tannins
Date: 1989-11-22 14:42:32 GMT

I believe the biggest factor governing tannin extraction during sparging is
pH. As the pH goes up, more and more tannins go into solution and appear in
the runnings. As the sparge water flows through the grains, less and less of
the acidic mash remains and so if the sparge water pH is relatively high or a
lot of sparge water is used, a point is reached where the pH of the runnings
gets too high and tannins dissolve readily leading to astringent flavors.

This is one reason why some experts recommend that you stop sparging when
the gravity of the runnings falls below a minimum (also of course because at
such low gravity you'd need to get a whole lot of runnings for just a little
more extract). More importantly from my experience, this is also why Miller
recommends adjusting the sparge water to a pH of 5.7 as insurance against the
pH of the runnings getting too high.

But how could a mechanical process like the liquid level maintenance gadget
Brian describes affect this situation? By, as he said, boosting extraction
efficiency. So less sparge water is used and the point of dilution where
tannin extraction occurs is never reached.

Keep in mind that the level maintenance gadget that Brian described is a
convenience (and a very nice one), but it is functionally equivalent to just
manually maintaining the sparge water level near the top of the grain. In
other words, if you are diligent about metering your sparge water you won't
have a lot of "dry" grain weighing down and packing your filter bed and so
you'll achieve the same effect.

- --Pete Soper

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