Q: Most of books or people’s experience say a mash out temp should be about 76-77 C and not exceeding 80 C as polyphenols from grain husk may/must be dissolved which causes harsh taste in finished beer. By looking at decoction involved with a third of thick mash being heating up to boil for 5-40 min and pumped back to main mash for temperature adjustment I would be curious if boiling mash is acceptable in decoction but not in mash out, or it is ok to heat mash out temp above 80 C without further harshness?
Understood the pH being raised up upon run-off would accelerate polyphenols dissolving especially above 80 C; therefore to control sparging temp at 76-77 C is important.
A: I have always wondered about that as well, I think there are some flavor differences between the beers that undergo decoction which probably does pick up some astringency, and those that use either single infusion or upward infusion mashing. For US-Canadian lagers the harshness of the polyphneol pick up might not reflect well in the overall light flavor profile desired, for higher BU German beers (30-35 BU) the astringency may actually be part of the flavor profile. Bitterness is a basic flavor and astringecy a mouthfeel but they are closely identified. So I think it depends on the beer you are brewing, higher BU beers like German pils or IPA would probably not be adversley affected and perhaps even benifit from some added astringency while, lighter more delicate beers may suffer.