Stirring the Mash: Could it affect Mash Extraction?

Unless someone can provide a reasonable mechanism how stirring a mash could restrict extraction efficiency, it is probably reasonable to assume that it does not, and your extraction increase came from something else.

Getting your pH right probably helped but 8% is a lot. By chance were you wearing no pants?

 

That's the only thing I could see that would produce such results.

 

I think that you were denaturing a portion of the enzymes in your mash by direct firing your kettle. not firing the kettle allowed for more enzymatic activity in the tun. That combined with a more desirable mash PH could account for an 8% efficiency gain.

 

How accurate is your volume measurement?

 

Did anything else change in your process/recipe? Grain crush, mash thickness, mash temp, stepped mash?

 

I agree that your probable root causes are in fact, the root causes. My guess is that temperature gradients can drastically affect your extraction - even if you think the temp is constant, those areas that are very warm / very cold will not have the same efficiency as other parts of your mash. A well insulated mash tun is the way to go. The act of stirring alone didn't cause the reduction I don't think - unless you were over heating, then overcooling when removing the lid to stir, etc etc. I was never very happy with my mash setup until I was well insulated. Now, I usually overshoot my target by a degree or two, then add back a bit of cold water until I nail it. It stays constant with no adjustments/stirring for 90 minutes no problem.

And yes, pH will affect your efficiency too...

 

Without repeating with every thing the same, including grains from the same bag, and only do the stir/not stir as the variable it is not conclusive.

Production breweries have mash tun rakes to make sure every thing is wetted, well mixed, and uniform. Some homebrewers use motorized set ups to stir the mash continuously.