wonderbread23
Well-Known Member
...but why not? Okay, well maybe I'm being a bit fictitious. Before I get yelled at...
I get the fact that it is probably a bad indicator of fermentation being complete since CO2 production can slow quite a bit towards the end and become so slight that the CO2 that is evolving goes unnoticed. This can lead to early bottling, drinking under-attenuated beer, and drinking beer that is probably not as good as it could have been. It is probably also a bad indicator of the start of fermentation since the time lags created during the reproductive phases of fermentation as well as the temperature of the ferment will cause the time from pitch to bubbling to vary. These reasons are probably enough to discourage hyper-active new brewers from eagerly ogling their airlocks for changes in an attempt to find meaning in the bubbles.
That being said, I propose that instead of blindly accepting the phrase in the title of this topic, we instead use the airlock as a practical tool to tell us that the main stages of fermentation are taking place...especially on buckets were active fermentation cannot be easily viewed. I want to get some ideas from those who are likely smarter than myself on the topic to make sure my logic / scientific understanding is sound.
The basic formula describing ethanol fermentation is:
Glucose → Ethanol + Carbon Dioxide
C6H12O6 → 2C2H5OH + 2CO2
With the basic pathway described above, I dont see how ethanol could be getting produced by yeast without a proportional amount of CO2 being produced. In theory the amount of bubbling would be proportional to the amount of ethanol being produced. During the cell reproduction phases, little CO2 is being produced, hence no increase in pressure and no bubbles. Once active fermentation starts however, there should certainly be some bubbling. Depending on the temperature of the fermenting beer, the time it takes for this will vary, but at some point it will hit the saturation levels for CO2 that the liquid can withhold and start off-gassing, increasing the fermentation pressure et voila bubbling.
Short of not having an adequate seal between the air lock and bucket (or lid, or grommet, or bung) I cannot see anyway possible that it would not bubble. If you know the rules, and possible reasons why its not bubbling, it seems like a pretty accurate indicator of activity.
I get the fact that it is probably a bad indicator of fermentation being complete since CO2 production can slow quite a bit towards the end and become so slight that the CO2 that is evolving goes unnoticed. This can lead to early bottling, drinking under-attenuated beer, and drinking beer that is probably not as good as it could have been. It is probably also a bad indicator of the start of fermentation since the time lags created during the reproductive phases of fermentation as well as the temperature of the ferment will cause the time from pitch to bubbling to vary. These reasons are probably enough to discourage hyper-active new brewers from eagerly ogling their airlocks for changes in an attempt to find meaning in the bubbles.
That being said, I propose that instead of blindly accepting the phrase in the title of this topic, we instead use the airlock as a practical tool to tell us that the main stages of fermentation are taking place...especially on buckets were active fermentation cannot be easily viewed. I want to get some ideas from those who are likely smarter than myself on the topic to make sure my logic / scientific understanding is sound.
The basic formula describing ethanol fermentation is:
Glucose → Ethanol + Carbon Dioxide
C6H12O6 → 2C2H5OH + 2CO2
With the basic pathway described above, I dont see how ethanol could be getting produced by yeast without a proportional amount of CO2 being produced. In theory the amount of bubbling would be proportional to the amount of ethanol being produced. During the cell reproduction phases, little CO2 is being produced, hence no increase in pressure and no bubbles. Once active fermentation starts however, there should certainly be some bubbling. Depending on the temperature of the fermenting beer, the time it takes for this will vary, but at some point it will hit the saturation levels for CO2 that the liquid can withhold and start off-gassing, increasing the fermentation pressure et voila bubbling.
Short of not having an adequate seal between the air lock and bucket (or lid, or grommet, or bung) I cannot see anyway possible that it would not bubble. If you know the rules, and possible reasons why its not bubbling, it seems like a pretty accurate indicator of activity.