Let's talk oxygen and when to use it

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WBC

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I have always used oxygen to give the wort and yeast a good start but sometimes I get a violent fermentation and others are quite mild. It has to do with many factors such as yeast type and OG strength. I just brewed a brown, the second day had a medium krausen and after 3 days it is barely fermenting and so I was thinking of an oxygen infusion to pick up the pace. How many of you have used oxygen after the initial pitching of yeast and how many days past pitching can you do this before you should stop the oxygen? I have not measured the gravity as it has not stopped fermentation yet on the 4th day of fermentation.

23 LBS total grain
Batch sparged
12 Gallon batch in 2 carboys
OG=1.058
Yeast is Safale s-04 1 pak in each carboy, No starter this time :rolleyes:
 
O2 is only necessary for the yeast to increase their cell count during the aerobic, adaptive phase of fermentation. Adding O2 after attenuation fermentation phase (anaerobic) has begun will only serve to oxidize the beer.
 
Supposedly, the ideal time is about 14 hours after pitching. By then, the least have put a big dent in the available O2 supply.
 
johnsma22 said:
O2 is only necessary for the yeast to increase their cell count during the aerobic, adaptive phase of fermentation. Adding O2 after attenuation fermentation phase (anaerobic) has begun will only serve to oxidize the beer.

That's what I always believed but some threads have talked about doing this with big beers and adding wort for 3 to 4 days but that's another topic.
 
With an OG of 1.054, it's inadvisable. When you get to high gravity/ABV (12%+) beers, it may be necessary, but these are extreme cases.
 
As long as you have sugar remaining, you can add oxygen. The yeast will use the oxygen and sugar to reproduce more. As previous posters have stated, the only time that this might be a help is for big beers.
 
Vermicous said:
As long as you have sugar remaining, you can add oxygen. The yeast will use the oxygen and sugar to reproduce more. As previous posters have stated, the only time that this might be a help is for big beers.

Sorry, but this is not true. The yeast only reproduce during the adaptive (aerobic) phase of fermentation in the beginning. They use up the oxygen during this phase while increasing their cell count and adapting to their surroundings in preparation for the next phase, attenuation. There is no oxygen needed during this phase for "normal" gravity brews.
 
And to elaborate even more, oxygenating your beer once the adaptive phase is over and active fermentation has begun exposes you to risk of off-flavours in the beer down the road. HSA might be dismissed as a potential problem, but not oxygenation in fermenting or post-fermenting beer. Once the yeast have been through their adaptive phase, they no longer scavenge oxygen at the same rate and it will oxidize compounds in the beer that may lead to premature staling and associated off-flavours. So the timing of oxygenation is critical.
 
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