PDA

View Full Version : oxygen or no oxygen?



laflaone
01-05-2013, 11:51 AM
Just started my first batch of cyser. Using a 6gal Better Bottle carboy.

Ingredients:
4 1/4 gal Musselmans apple cider
10lb honey
8g lalvin #1116 yeast
10g go-ferm in starter
measured SG is 1.111

Pitched yeast 2 days ago, and bubbling away. My question is whether or not to leave open to air for oxygen. I have read several "how to's", and they recommend doing that. I also see that it is standard to put a cork with an airlock, which will tell you how many bubbles you are getting but obviously will keep any air from getting in.

If it should be left open, how long before placing the airlock?

Medsen Fey
01-05-2013, 01:12 PM
The yeast need exposure to oxygen during the early part of fermentation to maximize their reproduction and their alcohol tolerance. Folks will typically stir/aerate the must for the first 1/3 of fermentation- in your case until the gravity gets down to about 1.075. In the case of apple batches, they often don't need as much aeration as the apple juice provides a lot of sterols and other growth promoters that tend to push the yeast to the max.

laflaone
01-06-2013, 08:38 AM
The yeast need exposure to oxygen during the early part of fermentation to maximize their reproduction and their alcohol tolerance. Folks will typically stir/aerate the must for the first 1/3 of fermentation- in your case until the gravity gets down to about 1.075. In the case of apple batches, they often don't need as much aeration as the apple juice provides a lot of sterols and other growth promoters that tend to push the yeast to the max.

Thanks for your reply. By "exposure to oxygen" would just leaving the stopper out be enough? Also, would covering the top with cheescloth be sufficient to keep contaminants out?

Medsen Fey
01-06-2013, 09:02 AM
Thanks for your reply. By "exposure to oxygen" would just leaving the stopper out be enough?


It might, but generally I will take a whisk and really whack the crap out of it to make sure the must is saturated with O2.

The cheesecloth will keep large particles and insects out, and that will work fine.

Siczek
01-07-2013, 09:29 PM
Is aeration really necessary with these dry yeasts? Most if not all dry yeasts for beer require no aeration. Are these yeasts prepared differently?

Medsen Fey
01-07-2013, 10:14 PM
The dry yeast have enough sterols for about 5-6 generations which is plenty for a 5-gallon batch with a gravity of 1.050. For batches that are starting with gravities of 1.100-1.150, if you don't aerate, your chances of a stuck fermentation are much higher. The yeast need to build a larger biomass and need better alcohol tolerance for meads, and to do that they need oxygen exposure to generate more sterols.

If you are concerned about oxidation just keep in mind that beer is MUCH more sensitive to oxidative damage. You won't harm a mead with oxygen during the first 1/3 of fermentation.

Siczek
01-08-2013, 09:22 PM
The dry yeast have enough sterols for about 5-6 generations which is plenty for a 5-gallon batch with a gravity of 1.050. For batches that are starting with gravities of 1.100-1.150, if you don't aerate, your chances of a stuck fermentation are much higher. The yeast need to build a larger biomass and need better alcohol tolerance for meads, and to do that they need oxygen exposure to generate more sterols.

If you are concerned about oxidation just keep in mind that beer is MUCH more sensitive to oxidative damage. You won't harm a mead with oxygen during the first 1/3 of fermentation.

Thanks, that makes a lot of sense. I appreciate a real (scientific) reply.