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Tannins during a decoction

TroubleShooting

Darrin Walraven • Greensboro, North Carolina asks,
Q

I have a question that’s been stumping me for a while. I’m an all-grain brewer and would like to try decoction mashing. All-grain brewers are always told to include a mash-out rest and to keep the mash temperature below 170 ºF (77 ºC) for risk of leaching tannins into the wort. So, how is it that a decoction mash requires part of the grist to be removed from the mash and boiled? What about the tannins?

A
This is a very good question that inevitably arises when knowledgeable all-grain brewers begin thinking about doing a decoction mash. The conventional rule is to mash-out at around 170 ºF (77 ºC)
Response by Ashton Lewis.