Author Topic: Second oxygen addition causes a pause in airlock bubbling  (Read 289 times)

Offline Richard

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Second oxygen addition causes a pause in airlock bubbling
« on: October 29, 2019, 04:43:29 PM »
I brewed a Russian Imperial Stout yesterday for the first time, and it was the highest-gravity beer I have brewed. I have read that it is good to add more oxygen after 12-24 hours because you can't get enough dissolved the first time around for a beer this big. This morning the airlock was bubbling rapidly so I added more oxygen at around 15 hours after pitching the yeast. I was surprised to see the airlock stop bubbling just after adding the O2. Over the course of the next couple of hours the bubbling rate gradually went back to what it had been. It makes sense that the addition of oxygen would essentially send the yeast back into the lag phase and cause a pause in the CO2 production, but I was not prepared to see it demonstrated so clearly.
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Offline jjw5015

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Re: Second oxygen addition causes a pause in airlock bubbling
« Reply #1 on: October 29, 2019, 04:49:48 PM »
it's more likely that opening the fermenter released all the pressure and it took a while for the headspace to fill back up and build enough pressure to release out the airlock.

Offline Richard

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Re: Second oxygen addition causes a pause in airlock bubbling
« Reply #2 on: October 29, 2019, 07:34:16 PM »
No, I have opened the fermenter before and it only takes a few seconds to build up pressure and start bubbling again. In this case I could see that there was pressure inside, just not enough to cause active bubbling. I have an S-shaped airlock and the liquid level was depressed on the carboy side right away.

Also, the RATE of bubbling was low. If it just needed to build up pressure, then after the first bubble the rate would have been the same as before. Instead there was an occasional bubble at first, with the rate gradually going back up to the previous value. That tells me that CO2 production was diminished temporarily.
« Last Edit: October 29, 2019, 07:51:58 PM by Richard »
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Offline Slowbrew

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Re: Second oxygen addition causes a pause in airlock bubbling
« Reply #3 on: October 30, 2019, 11:04:04 AM »
It's possible (and keep in mind I spit balling) that adding the oxygen knocked more CO2 than we might think due to inserting the wand or tubing and basically stirring the wort. 

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Offline Visor

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Re: Second oxygen addition causes a pause in airlock bubbling
« Reply #4 on: October 30, 2019, 03:17:05 PM »
   According to a brewing microbiology class I took last year, yeast have 2 metabolic pathways available to use/metabolize sugar, cellular respiration [exponential growth] and fermentation. In the presence of free oxygen they will almost always opt for cellular respiration as it uses the available food [sugar] many times more efficiently than fermentation. The C.R. pathway produces only a fraction of the CO2 that fermentation does. Your experience would seem to fit what we were taught.
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