Aerating prior to repitching yeast

[Hopadd]

Ok, first time with a stalled fermentation, ck'd SG, decided to repitch, do you add oxygen/aerate prior, or go as is?
This is 3 days into ferm. OG .040, SG at 3 days =.030, no action, used rehydrated 05.

 

[myndflyte]

What temp are you fermeting at? I'd lean more towards leaving it for 4 more days and see if you're still at 1.030. It may just be a little slow right now.

 

[Yooper]

You're using an accurate hydrometer, and not a refractometer?

 

[smata67]

No. Do not aerate at this time. Dry yeast doesn't need it.

 

[Hopadd]

So, if one was to repitch with a harvested yeast (liquid), would you aeriate prior?

 

[Vale71]

More importantly, aerating beer will cause an inordinate amount of oxidation, so much that you'd just be better off dumping the batch altogether. This has absolutely nothing to do with dry vs. liquid yeast, BTW.

 

[smata67]

Yes, you would aerate the liquid yeast in a starter (1L or larger) to get it going prior to pitching into your stalled 5 gallon batch. If you are using a stir plate, this will provide adequate oxygen. If you are making a starter without a stir plate, agitate or use supplemental oxygen like an air pump or O2 bottle. Pitch in 24-36 hours. If using dry yeast, just pitch directly, dry yeast does not need a starter or aeration. Do not aerate the 5 gallon batch at this point, undesirable oxidation may result.

 

[Hopadd]

Yes, you would aerate the liquid yeast in a starter (1L or larger) to get it going prior to pitching into your stalled 5 gallon batch. If you are using a stir plate, this will provide adequate oxygen. If you are making a starter without a stir plate, agitate or use supplemental oxygen like an air pump or O2 bottle. Pitch in 24-36 hours. If using dry yeast, just pitch directly, dry yeast does not need a starter or aeration. Do not aerate the 5 gallon batch at this point, undesirable oxidation may result.

Thank you, I use a stir plate, I was meaning, the wort. Thought more oxygen would be needed for the yeast to hopefully finish the job.

 

[hottpeper13]

I have greater(not always) success by pitching a starter at high krausen, like smata67 says. I do 800 ml or so.

 

[smata67]

Have you measured SG again? Hopefully it was just a slow start and you are back on track and don't need to do anything. S05 is reported to be sometimes sluggish early in the process. You should not rely on lack of airlock activity as a sign of stalled fermentation.

Well, you should have aerated at pitch time (though that is optional for dry yeasts) and that oxygen should still be available. But if you didn't aerate, pitching a dry yeast is fine, because it does not require aeration per the manufacturer. By pitching a starter of liquid yeast after about 24 hours on the starter, the yeast are primed and ready to get to work which helps with the fact that there was no aeration, if that was the case.

You should always avoid introducing oxygen into the beer after pitching. No aeration, splashing, stirring etc. The only exception is when brewing very high gravity beers, let's say 10%, there is a technique where the beer is re-aerated after 12 hours as the huge yeast population quickly consumes available oxygen. But there is plenty of yeast coming in after that point to make use of the extra oxygen.