Yeast Aeration - Air or Oxygen

[MarshmallowBlue]

Hello folks. I had a though and I was wondering if you could help me out.

So when aerating wort/ must. You are dissolving the oxygen into solution. I've read that yeast also need nitrogen. Now I know that a good chunk of the air we breathe is nitrogen. Is this dissolved into solution as well, and if so, does it count towards YAN?

If it does, wouldn't it be better to aerate with air instead of a pure oxygen setup?

 

[peterj]

Gaseous nitrogen found in air is N2 and is an inert gas. So it can't really be dissolved in anything. The nitrogen that the yeast uses is found in other nitrogen containing molecules that come from the grain or from added yeast nutrient. I'm not sure what YAN is but I think you are meaning FAN (free amino nitrogen). This is one of the main sources of nitrogen for the yeast. It's basically nitrogen that is part of an amino acid or small group of amino acids.

 

[MarshmallowBlue]

YAN is yeast accessible nitrogen, I think?

 

[peterj]

YAN is yeast accessible nitrogen, I think?

Oh ok, I've never heard of it before. I just searched for it and found this: http://en.wikipedia.org/wiki/Yeast_assimilable_nitrogen. Looks like that is the total of all the nitrogen sources (amino, ammonia, and ammonium). I learn something new every day!

 

[ajdelange]

It is FAN + ammonium (at beer pH all ammonia will be converted to ammonium ion). In brewing we rely on the maltster to modify his malt enough that there are low molecular weight peptide fragments and if we don't trust him do a protein rest. Some brewers add yeast nutrients which contain things like yeast hulls and diammonium phosphate to augment FAN and NN4+. Brewers serious about oxygenating their worts use pure oxygen. Thus the bottom line is that the N2 in air is not a factor in supplying nitrogen to beer yeast.

 

[MarshmallowBlue]

Well this is for a mead so there is no grain to provide nutrients to the yeast. It was just a thought I had given there's so much nitrogen in air, but not being a chemist I didnt know if yeast could access it. Thanks peter and ajadj

 

[ajdelange]

I'm not much of a mead maker but I think there is some protein in honey. Can't be much though. I have made a couple of batches and don't remember adding yeast nutrients but maybe I did. But then again I didn't aerate the must either that I recall.