View Full Version : Aerating During Fermentation - Bad? Why?

12-07-2016, 11:33 AM
So my aerator died, and I bought a new one. On the box, it says explicitly "Aerate before fermentation. Aerating during fermentation can lead to off flavors."

Anyone know why this would be? Certainly, aerating after the yeast have switched to their anaerobic life cycle I could understand, but as long as you're in the aerobic stage of their life cycle I can't see why it would hurt. My best guess for this warning is because many brewers don't really pay attention to the sugar breaks and micromanaging the life cycles like mead makers tend to. So they would be much more prone to letting the aeration run too long. Sort of like when they put warning labels on bleach. Well, yeah, no crud I shouldn't drink it..... ;)

Thoughts? Something I'm missing?

- Brett

12-07-2016, 12:11 PM
I have always aerated at pitch and 24 hours later.

I imagine this warning is for wine makers as their situation is different than ours.

12-07-2016, 05:50 PM
I wonder if the warning is for brewers. Brewers conventionally aerate before they pitch their yeast and then bang home a bung and airlock. I suspect that the long chain sugars in their wort - sugars that ale and wine yeasts cannot get at - are sending all kinds of signals to brett (the bacterium, not the OP) and other bacteria that will be unaffected by the acidity and the alcohol that the yeast is producing. Wine makers (and I include mead makers) are far less concerned because the only sugars we typically get involved with are those sugars that our yeasts can fully ferment and so those bacteria have no real chance of gaining a toe hold in the must...and speaking for myself, I aerate (stir my wines and meads) twice a day while the liquor is in the primary and indeed, have my primaries typically loosely covered with a towel