--- In email@example.com
, Brad McMahon <bmcmahon@...>
> It does this even at the small scale. When you are talking about
> and anaerobic fermentation you are talking about dissolved oxygen.
> you pitch the yeast you want lots of dissolved oxygen, that is why
> aerate it first. Once the dissolved oxygen is used up, the yeast
> then switch to anaerobic reproduction - that's when it uses sugars
> food source.
> Whether you have the lid on or not will make no difference to the
> fermentation process.
Much as we would like this to be the case, I'm afraid it ain't.
Have you ever watched what's going on in a (small) fermenter that's
open to atmosphere (ie no lid)? Yeast cells in clumps continually
rise to the surface riding on the bubbles of CO2 they are
producing. This puts them in direct contact with any oxygen (air)
that happens to be at the surface.
True, there can be a blanket of CO2 at the surface, as it is heavier
than air. But what happens when ambient breezes blow this away?
Air gets to be in surface contact, yes? And in contact with the
aforementioned yeast clumps.
That's how come the yield can be way down, and the amount of yeast
in the mash increases more than normal, because the yeast has access
to oxygen and propagates, rather than be in a completely anerobic
(no air) environment producing alcohol.
Try one as an experiment. Set up 2 20 litre fermenters exactly the
same, one with a lid & airlock as usual, the other without.
Preferably the lid should be clear plastic or glass, so you can see
what's going on. Observe the difference in the way the yeast
performs in the open fermenter. Then when they have run their
course, check the amount of yeast slurry in each fermenter. Distill
each as normal, recording your temps, yields etc.
Then report back here the differences. I've got a bottle of 12yo
Glenfiddich as a prize if you can show no difference in yields of
ethanol or yeast slurry. :-)