thehopbandit
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I have been reading through some old threads and it seems that there is still some debate on this topic.
Let's say I ferment a beer at a pretty constant 68F. It finishes fermentation and I cold crash it for a number of days at 40F. Fast forward to bottling time and the priming sugar calculation. One needs to determine the residual CO2 in the beer. Do I want to use the temperature at the time of bottling, or the temperature the fermentation finished at?
We know that warm beer can hold less CO2, and cold beer can hold more CO2. However, there has to be the CO2 available in the first place to be able to dissolve into this colder beer.
I have read convincing answers to both sides of the story. The logic I am working through is this:
If you are fermenting at 68F and it finishes out, it will no longer be producing CO2 after this point. There will be some CO2 retained in the beer and some CO2 in the headspace of the fermenter, but no "new" CO2 will be created. If you now cold crash the beer down to 40F, Henry's Law says that more CO2 should dissolve into the wort. However, no new CO2 is being created. The fermentation is done. The only CO2 available for dissolving is the small amount still in the headspace that isn't pressurized enough to leave the fermenter through the airlock. It's not like a keg that is continually forcing a pressurized CO2 on the wort, making it dissolve more. Even if this amount in the headspace dissolves into the beer, it seems negligible in the grand scheme of things.
On the other side of things, warm beer holds less CO2. If you were to warm the beer (for whatever reason) to above 68F, you now have existing CO2 leaving the liquid and possibly exiting through the airlock. Even if you lower the temp back down, there isn't really the CO2 available to dissolve back into the beer. It left through the airlock. So, it seems like you want to use the warmest temperature the beer was after fermentation, right? Same thing when you cool the temperature after fermentation. You only have a little bit of CO2 in the headspace available for dissolving.
So, it seems to me, that you would want to use the temperature the fermentation finished at or, in other words, the highest temperature? Is my logic correct on this?
What do you think?
Let's say I ferment a beer at a pretty constant 68F. It finishes fermentation and I cold crash it for a number of days at 40F. Fast forward to bottling time and the priming sugar calculation. One needs to determine the residual CO2 in the beer. Do I want to use the temperature at the time of bottling, or the temperature the fermentation finished at?
We know that warm beer can hold less CO2, and cold beer can hold more CO2. However, there has to be the CO2 available in the first place to be able to dissolve into this colder beer.
I have read convincing answers to both sides of the story. The logic I am working through is this:
If you are fermenting at 68F and it finishes out, it will no longer be producing CO2 after this point. There will be some CO2 retained in the beer and some CO2 in the headspace of the fermenter, but no "new" CO2 will be created. If you now cold crash the beer down to 40F, Henry's Law says that more CO2 should dissolve into the wort. However, no new CO2 is being created. The fermentation is done. The only CO2 available for dissolving is the small amount still in the headspace that isn't pressurized enough to leave the fermenter through the airlock. It's not like a keg that is continually forcing a pressurized CO2 on the wort, making it dissolve more. Even if this amount in the headspace dissolves into the beer, it seems negligible in the grand scheme of things.
On the other side of things, warm beer holds less CO2. If you were to warm the beer (for whatever reason) to above 68F, you now have existing CO2 leaving the liquid and possibly exiting through the airlock. Even if you lower the temp back down, there isn't really the CO2 available to dissolve back into the beer. It left through the airlock. So, it seems like you want to use the warmest temperature the beer was after fermentation, right? Same thing when you cool the temperature after fermentation. You only have a little bit of CO2 in the headspace available for dissolving.
So, it seems to me, that you would want to use the temperature the fermentation finished at or, in other words, the highest temperature? Is my logic correct on this?
What do you think?
