Bottle Conditioning Lager Question

[bill_face]

Hello all,

Currently I have some lager at the end of lagering stage at ~0C. It was fermented at 10C. I'm wondering whether to let it warm back up to fermentation temperate before priming and bottling?

According to the priming calculator i use if i enter a lower number for beer temperature i need to use less sugar.

Just wondering what the theory is behind that also

In the past i have made a mistake with this conundrum and made some flat lager, but never figured out the details.

 

[Deadhead]

How long have you been lagering? There should be some yeast still, but you may not have enough (hence flat lager). You will need warmer temperatures to get it to prime up. I actually prime and condition before I lager, but I realise that's a lot harder space wise.

 

[bill_face]

Been lagering for a month. I don't think the amount of yeast is so much of an issue as ebtering the correct numbers into the calculator. Comparing 1C to 10C means adding twice the amount of sugar (for the warmer temp)

 

[bill_face]

Been lagering for a month. I don't think the amount of yeast is so much of an issue as ebtering the correct numbers into the calculator. Comparing 1C to 10C means adding twice the amount of sugar (for the warmer temp)

From the priming calculator notes:

Carbon dioxide (CO2) is a gas produced as a byproduct of fermentation. Although we generally add more CO2 for drinking our beer via priming sugar or by force carbonating, there is CO2 present in the fermenter after fermentation. Temperature is important in this, as liquids "hold" more CO2 when cooler, and release more when the liquid is warmer. The equilibrium in the fermenter under airlock therefore is pressure and temperature dependent. Warming the beer in the fermenter will then make the airlock bubble, as a sign of CO2 being released.

Calculator is at: Beer Priming Sugar Calculator | Brewer's Friend

 

[bill_face]

So by my understanding there would have been a certain amount of CO2 present at the end of fermentation at 10C.

The question is did the amount of CO2 held increase when lowering the temperature for lagering? And would it decrease if i raised it again?

I would guess that the answer to both of those questions is no, and i should enter 10C into the calculator and not worry to much about the temperature when priming & bottling

 

[Deadhead]

Ahh, a month isn't long so there should still be yeast for priming.

I am not sure on the temperature differences in priming, as I (rightly or wrongly, I dunno!) always carb at around 18C ,but control my conditioning temperatures more.

 

[Jan.]

The question is did the amount of CO2 held increase when lowering the temperature for lagering? And would it decrease if i raised it again?

This is exactly the right question to ask.

The amount of CO2 will only increase if the beer is either currently fermenting or under pressure (under pressure with a higher level of CO2 being exerted on it which will force the CO2 into solution). This means that if you finish the fermentation at 10C, you will need to put 10C in your priming calculator (obviously). If you then let it rise to 20C and add the priming sugar at this temp. 20C is what you add. However, (and sorry to have rambled a bit) if you then decrease the temperature again to let's say 10C, the CO2 will NOT increase as it is not under pressure nor is it producing additional CO2 and therefore, in the priming calculator, you still need to put 20C even if the beer is at 10C when you prime.

You always have to input the maximum temperature that the beer has reached at any time after fermentation has stopped.

The other issue is that the yeast will prefer to carbonate at a higher temperature. Lager yeast actually prefers a much higher temperature than the one we ferment it at. We normally ferment cold to reduce yeast flavour but lager yeast actually prefer a higher temperature.

 

[Alastair70]

Like @Deadhead when I carb lager I do it at 18C. I have gone out to 4 weeks in the past, but now I’ll carb the bottles at packaging time then lager after 2 weeks at room temp. It makes more sense on many levels.

 

[bill_face]

This is exactly the right question to ask.

The amount of CO2 will only increase if the beer is either currently fermenting or under pressure (under pressure with a higher level of CO2 being exerted on it which will force the CO2 into solution). This means that if you finish the fermentation at 10C, you will need to put 10C in your priming calculator (obviously). If you then let it rise to 20C and add the priming sugar at this temp. 20C is what you add. However, (and sorry to have rambled a bit) if you then decrease the temperature again to let's say 10C, the CO2 will NOT increase as it is not under pressure nor is it producing additional CO2 and therefore, in the priming calculator, you still need to put 20C even if the beer is at 10C when you prime.

You always have to input the maximum temperature that the beer has reached at any time after fermentation has stopped.

The other issue is that the yeast will prefer to carbonate at a higher temperature. Lager yeast actually prefers a much higher temperature than the one we ferment it at. We normally ferment cold to reduce yeast flavour but lager yeast actually prefer a higher temperature.

So, my lager's maximum temp so far is 10C. If i carbonate at 18C would i use that temp for priming calculation? Or 10C as it will be cooled back down before serving?

 

[Alastair70]

Yes, 18C is the temp that goes into the calculator.
The residual yeast still in suspension will make CO2. Then refrigerate the bottles for a couple of weeks before serving. This allows the beer to clear and maximise the amount of CO2 that gets dissolved.

 

[foxy]

It all depends on if the beer is cold crashed, yes, CO2 in the beer in the fermenter is at equilibrium with the CO2 above but take that down to cold crash temperature the CO2 is drawn back into the beer. So if you fermented at 20 C crashed down to 1or 2 degrees for a few days the CO2 will be absorbed back into the beer retaining more CO2 than when it was when it was 20C
My general rule of thumb will be 25 to 28 gram of sugar to prime to 1.8 volumes of CO2 in a 21 litre batch at 3-4 C

 

[Jan.]

I have always believed that the CO2 will not get absorbed back into the beer when cold crashing unless it is actively still generating CO2, or the beer is under pressure by the CO2 (will not be absorbed to a significant level anyway). So you should put the maximum temperature that the beer has got to at any stage since the fermentation has stopped.

 

[foxy]

I have always believed that the CO2 will not get absorbed back into the beer when cold crashing unless it is actively still generating CO2, or the beer is under pressure by the CO2 (will not be absorbed to a significant level anyway). So you should put the maximum temperature that the beer has got to at any stage since the fermentation has stopped.

Why do you think suck back occurs? Close a vessel where the pressure is at equilibrium. Put in the fridge take down to 1C, the sides will suck in. Why? The gas has been reabsorbed into the beer. See what Kai from Braukaiser says on Brewers Friend.
* Temperature of Beer used for computing dissolved CO2:
The beer you are about to package already contains some CO2 since it is a naturally occurring byproduct of fermentation. The amount is temperature dependent. The temperature to enter is usually the fermentation temperature of the beer, but might also be the current temperature of the beer. If the fermentation temperature and the current beer temperature are the same life is simple.

However, if the beer was cold crashed, or put through a diacetyl rest, or the temperature changed for some other reason... you will need to use your judgment to decide which temperature is most representative. During cold crashing, some of the CO2 in the head space will go back into the beer. If you cold crashed for a very long time this may represent a significant increase in dissolved CO2. There is a lot of online debate about this and the internet is thin on concrete answers backed by research. We are open to improving the calculator so please let us know of any sources that clarify this point.

 

[Jan.]

You are right, the sides do suck in when the temperature drops and this will reabsorb some air; but not much. A 20 litre vessel will suck back what? half a litre? 1 litre being really generous? so 5% (this is an estimation but please let me know if you disagree, let me know how much suckback you get). If the full 5% volume of CO2 was reabsorbed into 20 litres that would increase the volumes of CO2 from (lets say) 1.5 to 1.575 an increase of just 0.075 volumes.

At 4C there are around 1.48 Volumes
At 20C there are around 0.87 Volumes

I used beersmith's priming calculator for these numbers but I presume most calculators will be similar. If you put 20 litres and 4C or 20C then the target volume, the amount of sugar necessary to get to these volumes will be almost zero. Maybe a gram or so descrepancy, feel free to use your own priming calculator.

Which means the increase in reabsorbtion (of 0.075 volumes) would increase the volumes of CO2 from 0.87 (20 litres at 20C) to 0.945.

So, you are inputting 4C into the priming calculator and the priming calculator thinks there are 1.48 volumes when you actually have 0.945. This is why it needs to be set at 20C (highest temperature reached after the generation of CO2). Otherwise the calculator starts assuming you have much less CO2 in absorbtion than you have.

In addition it won't just be CO2 as CO2 doesn't completely stratify, although there would be more CO2 in the FV than in the air, it is still always going to be mixed with its other components.

Suck back also occurs as water is at it's most dense at 4C, therefore there is some shrinkage of the actual liquid which causes suckback/the sides caving in a little as well.

Bearing all this in mind, I don't think the amount of CO2 that will be re-absorbed into the liquid is really going to contribute very much and therefore, as I mentioned, wouldn't be significant. Whereas the temperature is.

I might be wrong, and if so please let me know as these discussions help everyone learn.

 

[foxy]

You are right, the sides do suck in when the temperature drops and this will reabsorb some air; but not much. A 20 litre vessel will suck back what? half a litre? 1 litre being really generous? so 5% (this is an estimation but please let me know if you disagree, let me know how much suckback you get). If the full 5% volume of CO2 was reabsorbed into 20 litres that would increase the volumes of CO2 from (lets say) 1.5 to 1.575 an increase of just 0.075 volumes.

At 4C there are around 1.48 Volumes
At 20C there are around 0.87 Volumes

I used beersmith's priming calculator for these numbers but I presume most calculators will be similar. If you put 20 litres and 4C or 20C then the target volume, the amount of sugar necessary to get to these volumes will be almost zero. Maybe a gram or so descrepancy, feel free to use your own priming calculator.

Which means the increase in reabsorbtion (of 0.075 volumes) would increase the volumes of CO2 from 0.87 (20 litres at 20C) to 0.945.

So, you are inputting 4C into the priming calculator and the priming calculator thinks there are 1.48 volumes when you actually have 0.945. This is why it needs to be set at 20C (highest temperature reached after the generation of CO2). Otherwise the calculator starts assuming you have much less CO2 in absorbtion than you have.

In addition it won't just be CO2 as CO2 doesn't completely stratify, although there would be more CO2 in the FV than in the air, it is still always going to be mixed with its other components.

Suck back also occurs as water is at it's most dense at 4C, therefore there is some shrinkage of the actual liquid which causes suckback/the sides caving in a little as well.

Bearing all this in mind, I don't think the amount of CO2 that will be re-absorbed into the liquid is really going to contribute very much and therefore, as I mentioned, wouldn't be significant. Whereas the temperature is.

I might be wrong, and if so please let me know as these discussions help everyone learn.

Well Kai got his calculator from here. Bottle Conditioning Calculator | Lallemand Brewing
But as he said in the Brewers Friend it needs one to use their own judgement, I tried adding more sugar initially because I felt I would be losing CO2 from the solution through movement even the stirring and the temperature may move a degree or so during the bottling. But in the end I found what the calculator predicted was pretty much spot on.

 

[Wynne]

Why do you think suck back occurs? Close a vessel where the pressure is at equilibrium. Put in the fridge take down to 1C, the sides will suck in. Why? The gas has been reabsorbed into the beer. See what Kai from Braukaiser says on Brewers Friend.
* Temperature of Beer used for computing dissolved CO2:
The beer you are about to package already contains some CO2 since it is a naturally occurring byproduct of fermentation. The amount is temperature dependent. The temperature to enter is usually the fermentation temperature of the beer, but might also be the current temperature of the beer. If the fermentation temperature and the current beer temperature are the same life is simple.

However, if the beer was cold crashed, or put through a diacetyl rest, or the temperature changed for some other reason... you will need to use your judgment to decide which temperature is most representative. During cold crashing, some of the CO2 in the head space will go back into the beer. If you cold crashed for a very long time this may represent a significant increase in dissolved CO2. There is a lot of online debate about this and the internet is thin on concrete answers backed by research. We are open to improving the calculator so please let us know of any sources that clarify this point.

If you put a sealed PET bottle full of air at atmospheric pressure (i.e, with no liquid in it) into a fridge at room temperature and take it down to 1C you will see exactly the same effect - the PET bottle will crush. The amount of pressure a given mass of gas will exert varies with temperature (Charles’ Law).

Whether any CO2 is re-absorbed into beer. during cold-crashing is an interesting question. On one hand, as the temperature drops the pressure of gas above the beer will remain constant (if kept at at atmospheric pressure) or reduce (if in a sealed fermenter). On the other, as you say, the solubility of CO2 in beer increases as the temperature is reduced. How these competing effects resolve themselves in a given set of circumstances is unclear to me. What are your thoughts?

 

[foxy]

If you put a sealed PET bottle full of air at atmospheric pressure (i.e, with no liquid in it) into a fridge at room temperature and take it down to 1C you will see exactly the same effect - the PET bottle will crush. The amount of pressure a given mass of gas will exert varies with temperature (Charles’ Law).

Whether any CO2 is re-absorbed into beer. during cold-crashing is an interesting question. On one hand, as the temperature drops the pressure of gas above the beer will remain constant (if kept at at atmospheric pressure) or reduce (if in a sealed fermenter). On the other, as you say, the solubility of CO2 in beer increases as the temperature is reduced. How these competing effects resolve themselves in a given set of circumstances is unclear to me. What are your thoughts?

I have done a few things over the years, I started collecting the gas from the fermentation a few years ago. Two reasons, one to prevent my beer served through the hand pump going off. The vacuum in the cask sucking in the gas instead of air, the other for cold crashing. As the falling temperature absorbed the CO2 then that co2 has to be replaced.
What Charlie Bamforth mentioned in one of his many podcasts, the ferment has to be robust. The gas and condensate removing all the unwanted volatiles and scrubbing any excess oxygen out of the solution. That got me thinking.
So do we want the excess volatiles and any unused oxygen being sucked back into the beer as it cold crashes? I don't think so. So what do I do now? I have gone back a few years and now put gladwrap over the top of the fermenter. Never had any problems before with oxidised beer and I haven't now, the question is, is air really getting sucked into the beer as it cold crashes? Or is air simply replacing the the CO2 getting sucked back into the cooling beer. I think that well may be the case, there is a mixture of air and CO2 above the beer. I do have a DO meter I really should check how much dissolved O2 is in the beer at bottling. The only other way around it is to use bottled CO2 to release into the head space during cold crashing, if it is really necessary???

 

[Birdsnestbrewery]

My understanding was that the suck back when cooling occurs due to the volume decrease with lower temperature, given that the pressure will remain the same in a non-sealed vessel.
I guess a tiny bit of CO2 could be absorbed back in by chance but if you are not pushing it in, nor actively generating CO2 I don't believe the lower temperature will cause the beer to become more carbonated.

 

[foxy]

My understanding was that the suck back when cooling occurs due to the volume decrease with lower temperature, given that the pressure will remain the same in a non-sealed vessel.
I guess a tiny bit of CO2 could be absorbed back in by chance but if you are not pushing it in, nor actively generating CO2 I don't believe the lower temperature will cause the beer to become more carbonated.

The chart which helps homebrewers to know what dissolved CO2 is in their beer at a given temperature would be formulated at 1 ATM otherwise it would indicate the pressure as well as the temperature. So it's logical to assume there is always pressure on the gas, even when the fermenter is open.
I use the chart as it is more use for anyone bottling, if I keg I use sugar and time to carbonate the keg the spunding valve will release any excess pressure, alternatively you can fast carb using CO2. I doubt that it is just the shrinkage of the beer in the vessel, I did see a photo of a LODO's brewers s/s keg he cold crashed without any positive pressure added the resulting vacuum completely destroyed the keg.