Direct fire, decoction, and boil additions

[Gregory T]

Things that make me go hmmm. My last BIAB was a 4 step mash Saison, I raised temp by adding boiling water through a calculator.


Clearly direct firing a mash tun will have the potential to scorch sugars. Wouldn’t boiling water or especially decoction basically shut down conversion for whatever comes into contact while it’s above 172°f?


Obviously this has been done for centuries, so it works. Just makes me curious


File under brewing mysteries along with what temperature to use for priming after a cold crash

 

[McKnuckle]

Decoction works because you are supposed to boil only the thickest part of the mash, that being the grain itself. The decocted grains should ideally have only enough fluid around them to keep them buoyant.

The enzymes are working in the liquid part of the mash, which is left behind in the mash tun waiting to be raised to the next temperature rest when the grains are returned. So they survive.

I have seen some people's decoction videos showing them removing large scoops of liquid wort along with the grains, and it always makes me do a facepalm.

 

[balrog]

along with what temperature to use for priming after a cold crash

Before cold crash, the liquid absorbed some CO2 created by yeast. The amount was determined by temp and pressure above the liquid. Cold crashing likely caused a little bit more of the CO2 above the liquid to be absorbed, due to lower temp at same pressure, but no more CO2 was introduced to the overall system unless you have one of those balloon capture devices set up. Plus, typically you don't hold cold crash days on end prior to kegging/bottling.

So I *THINK* you use the temp at which the liquid fermented highest (if you ramped temp near end of fermentation you will have driven CO2 from solution, because of higher temp at supposedly same temp.

 

[RM-MN]

Most modern grains have such high diastatic power that the fact that your hot decoction denatures some of them doesn't matter. Direct firing causes a problem because the mash is too thick to circulate naturally so you have to stir to keep the temperature near the same. It will be hard to homogenize that mash temp to hit the right temp and stop the heating before it overshoots.

 

[Gregory T]

That’s what I did with my Tripel I bottled last week. Though I shot at 3 instead of 3.25 just in case. It’s in Belgian bottles so should be ok even if it goes higher than I expected

There is so much contradictory info on that. But your view makes sense. I cold crashed with aluminum foil over the airlock hole. No new CO2 should be produced, therefore I think primary temperature as well

We shall see in a couple weeks

 

[BigEd]

Clearly direct firing a mash tun will have the potential to scorch sugars. Wouldn’t boiling water or especially decoction basically shut down conversion for whatever comes into contact while it’s above 172°f?

You are only boiling a portion of the mash at any one time(about 1/3 by weight) during decoction steps. As has been stated in another post mostly grain is removed leaving behind the majority of the enzymes in the liquid solution. Yes, whatever enzymes are in the portion that is boiled will be de-natured. However, before reaching boiling temp this pulled fraction should be exposed to some time at mash conversion temps so all of the original grain is exposed to saccharification rest stage.

 

[Vale71]

I have seen some people's decoction videos showing them removing large scoops of liquid wort along with the grains, and it always makes me do a facepalm.

There's really no need to keep slapping yourself. Modern malts have such strong diastatic power that you don't really need to pull a thick mash and needlessly risk scorching. Even if you pull a homogeneous mash you'll still have plenty of enzymes available in the mash tun to finish converting. Commercial breweries that still employ a traditional decoction mash process simply pump the right amount of mash to the boil kettle for decoction while continuosly stirring to ensure that the water to grist ratio will be the same in both kettles. With large volumes there is really no way to actually pull a thick mash ever since pumps and automation have replaced the brewmaster manually pulling the decoction with paddle and scoop.

To the OP: it's still important to add the decoction/boiling water slowly while stirring continuously to prevent the formation of temporary hot pockets where enzymes might be further damaged by temperature.