Decoction mashing, does it not add bitter off flavors?

[Bonde]

Or am I completely off.

I mean, when I started brewing I used to sparge with water almost at boiling temperatures, and ended up with extreme off flavors and bitterness due to tannins extracted from the dark grains because of the way too hot water I’ve been told.

What’s the difference with decoction when pulling a decoction, boiling and then adding it to the mash again. Or am I just missing that the a decoction normally goes to a 82c max temp? been reading a few places where it just says boil, and no temperature indications.

 

[Colby]

When you say 'near boiling water', are you saying 200F+?

 

[Yooper]

Ah, when we say "Never boil the grains!" and then talk about decoctions, it sounds contradictory.

But it isn't, believe it or not. Here's why- it has to do with pH. The reason you don't sparge over 170 degrees is because the grain and water at that time is pretty "thin" in the mash(sparge) and the high heat combined with a relatively high pH can extract tannins from the husk of the grain.

When you do a decoction, first, it's a portion of the grain not the whole amount. So, even if you did pull some tannins, it wouldn't be that much. Secondly, when you decoct, you pull a very thick (mostly grain) portion, bring that up to saccrification rest temperatures, hold it and then boil it and add it back to the mash. The key is to pull a thick decoction, NOT the thin liquor from the mash. That keeps the pH low, and avoids tannin extraction.