Does heating BIAB vessel deactivate enzymes?

[crippled1]

Misconceptions - Brew Bag Myths Explained

I am planning to maintain temp and raise it at end of mash by using my stovetop burner.
As it heats up I drain via bottom valve and just pour it over the grain bed.
The attached link states if I heat it to 170 it deactivates the enzymes that get superheated.
I dont agree with that.
If that was the case then a decoction mash would never work.
I have always added bottom heat to raise temp.
Is this not the best practice?

 

[RM-MN]

Enzymes have a range of temperature in which they work and a temperature at which they stop working and are denatured so they cannot start again. Both alpha and bety amylase are slowly denatured at temperatures over about 160F. and as the temperature goes up denaturing happens sooner. When you heat the BIAB kettle from the bottom you almost certainly denature part of the enzymes but most mashes contain excess amounts of the enzymes so the mash continues to work even with some of the enzymes destroyed.

To keep from denaturing the enzymes while adding heat in a BIAB kettle, constant and vigorous stirring are necessary and even that may not be enough if high heat is applied.

Now for the question, why do you want to add heat? If it is for a step mash, do a lot of research on that subject as you may find that it provides little gain to the beer. If it is just to maintain mash temp, check how much time it takes for full conversion because after you have reached that the temperature isn't critical.

 

[Vale71]

In a decoction you don't decoct the whole mash but only 1/3rd to 1/4th of the total mash. The part of the mash that doesn't get decocted retains its enzymatic power although the total enzymatic power is reduced with every decoction. This never becomes an issue as decoction schedules last much longer and enzymes have therefore a lot more time to do their work.

When performing a stepped mash schedule if your recirculation is not adequate it's possible to cause localized overheating that will prematurely destroys enzymatic activity. Whether this will lead to incomplete conversion depends on the severity of the overheating.