Oxygen suckback during cold-crashing

Tunabeast · Jan 18, 2019

In my quest to keep as much O2 away from my hoppy beers as possible I have discovered a source of considerable ingress is during cold crashing.

Post fermentation, as you'd expect, the headspace of the vessel is pure CO2. When the beer is cold crashed to say 1 or 2 degC the solubility of the CO2 increases dramatically and readily dissolves into it. That gas volume has to be replaced or you end up with a vacuum. Chances are if you're using an airlock then oxygen is pulled back through the airlock into the FV, where it contacts the beer (the air will mix with the CO2, not sit on top of it).

My question is, if I am kegging, is it even worth cold crashing? I imagine after say 4 days of primary dry hopping/diacetyl rest gravity will drop most of the sediment and yeast out - or would it?

Has anyone come across any DIY solutions to stop oxygen suckback, using a bladder or balloon of some sort filled with CO2?

I know It might seem pedantic but really do want as little oxygen contact as possible!

foxbat · Jan 18, 2019

One solution would be to use a very long coiled up blowoff tube. How long is long enough though?

I don't personally bother cold crashing any more because the yeasts I use are flocculent enough that the beer is bright in the fermenter after primary fermentation. I go straight from the valve on the FV to a CO2 flushed keg and I don't suffer oxidation or colour shifts over time.

BeerCat · Jan 18, 2019

There is a new product that stops suck back. The airlock pokes into it. Was on David Heaths channel a few months ago. Called Plato i think. About a tenner. Was going to buy some but i only have about half a cm clearance left.
I cold crash the majority of my beer for at least a week and not noticed any oxidisation. I would take steps to eliminate the possibility though if i could/can.

Ajhutch · Jan 18, 2019

I saw somebody post on on twitter a few months back and I managed to find it now. He rigged up two mason jars in line with blow off tube style grommets. Filled the first jar with star san and piped in his blow off tube. The star san was pushed to the second jar during fermentation, and then sucked back during cold crashing. I guess the use of two jars in this way enables you to monitor how much CO2 has been produced, and act accordingly if you are going to run out of space. You could always rig this system up with plastic rather than glass.

Tunabeast · Jan 18, 2019

Good suggestions, some other ideas - http://brulosophy.com/2018/05/10/7-methods-for-reducing-cold-side-oxidation-when-brewing-beer/

Braindead · Jan 18, 2019

My last brew I came up with what I consider a genius idea.
I used the Hydration Bladder from my Camelbac, filled that with CO2 and then attached that to the top of the corny bung thingy.
A few beers before this idea I had pure suck back, I'm taking 1/2 litre of dirty yeasty water. Weird thing is it was one of my best brews .lol

http://rover.ebay.com/rover/1/710-5...0001&campid=5338413729&icep_item=312239908094

BeerCat · Jan 18, 2019

Here is the item > Plaato Valve Homebrew Product Review
I wouldn't mind trying the 2 jars method if i can make space in the fridge.

Dutto · Jan 18, 2019

Personally, I cannot remember a single brew that has gone off because a bit of air has bled back into the FV during cold crashing.

At the moment I am still drinking a Robust Porter that was bottled about a year ago. Each 650ml bottle was full of air before 95% of it was displaced by the Porter; and even after a year it's still a palatable drink.

To get a similar amount of air into an FV as a result of cold crashing would be virtually impossible!

Sorry, but I think some people look for solutions to problems that only exist in their imaginations.

Bigcol49 · Jan 18, 2019

Dutto said:
I think some people look for solutions to problems that only exist in their imaginations

Tunabeast · Jan 18, 2019

Dutto said:
Personally, I cannot remember a single brew that has gone off because a bit of air has bled back into the FV during cold crashing.

At the moment I am still drinking a Robust Porter that was bottled about a year ago. Each 650ml bottle was full of air before 95% of it was displaced by the Porter; and even after a year it's still a palatable drink.

To get a similar amount of air into an FV as a result of cold crashing would be virtually impossible!

Sorry, but I think some people look for solutions to problems that only exist in their imaginations.

NEIPA styles have more volatile chemicals derived from hops which are susceptible to oxidation than less hop focused beers - this is why every possible source of O2 ingress is a worthy consideration IMO

terrym · Jan 18, 2019

Dutto said:
Sorry, but I think some people look for solutions to problems that only exist in their imaginations.

.

Ajhutch · Jan 18, 2019

And sometimes problems do exist but when people haven’t experienced them they assume that nobody else has either.

Bigcol49 · Jan 18, 2019

Ajhutch said:
And sometimes problems do exist but when people haven’t experienced them they assume that nobody else has either.

Hi!
I have always cold-crashed and have never experienced any problems from oxidation.
@Tunabeast try replacing the airlock with a solid plug; any CO2 that dissolves into the beer will create a vacuum and suck the lid tighter onto the FV.
I assume that you have read this: http://brulosophy.com/2018/05/10/7-methods-for-reducing-cold-side-oxidation-when-brewing-beer/

Ajhutch · Jan 18, 2019

I don’t want to get into another anecdote v science argument so I’m not going to address the ‘is this a real problem’ question further.

For those interested in answering the question rather than arguing that it doesn’t need to be answered, I found the picture I referred to in my previous post. I noticed that there was an airlock on the second jar which explains why it doesn’t all just explode. Perhaps he removed the airlock and replaced it with a bung when he crashed it, or else oxygen would be reintroduced. But whenever you remove and airlock to replace with a bung, during the time in between oxygen can enter the system. So I don’t know really!

Could you calculate the ‘suck back’ CO2 volume with reference to the cooling shrinkage from fermentation temp to cold crash temp? If so then you could know if there was enough in jar 1 and clamp off the tube between jars 1 and 2 maybe?

Tunabeast · Jan 18, 2019

Bigcol49 said:
Hi!
I have always cold-crashed and have never experienced any problems from oxidation.
@Tunabeast try replacing the airlock with a solid plug; any CO2 that dissolves into the beer will create a vacuum and suck the lid tighter onto the FV.
I assume that you have read this: http://brulosophy.com/2018/05/10/7-methods-for-reducing-cold-side-oxidation-when-brewing-beer/

Col only thing that concerns me is I don't want my FV crumpling under vacuum, I've seen it happen on a much bigger scale and it doesn't take a lot!

Yes read that article, quite like the idea of creating a positive pressure using CO2 but fear it would end up consuming quite a bit and running down my cylinder.

terrym · Jan 18, 2019

If you have a gas space above the beer in the FV of about 3 litres and it starts at 20*C and no more CO2 is being generated by fermentation and that is allowed to cool to 4*C two things can happen. A vacuum is drawn or gas is drawn in to maintain the pressure. If it is the latter the theoretical volume shrinkage from the original 3 litres is 3000 x 277/293 = 150ml approx. So there is a a potential to suck in 150 ml air. Since the oxygen concentration in air is about 21%v/v this equates to about 31ml of pure oxygen gas which is about 32 x 31.5/22400 = 45mg (milligrammes). Assuming this 45mg can reach the surface of the beer by Brownian motion or small convection currents, it will struggle to venture deep into the beer, since it is more likely to set up a concentration gradient that works against it. And oxygen itself does not dissolve very well in aqueous solutions unlike CO2 which dissolves by forming carbonic acid in a reversible reaction.
If anyone disagrees with any of this please let us know. I have been known to get things wrong wink...

Otherwise draw your own conclusions as to how real this problem actually is.

britton · Jan 18, 2019

terrym said:
If you have a gas space above the beer in the FV of about 3 litres and it starts at 20*C and no more CO2 is being generated by fermentation and that is allowed to cool to 4*C two things can happen. A vacuum is drawn or gas is drawn in to maintain the pressure. If it is the latter the theoretical volume shrinkage from the original 3 litres is 3000 x 277/293 = 150ml approx. So there is a a potential to suck in 150 ml air. Since the oxygen concentration in air is about 21%v/v this equates to about 31ml of pure oxygen gas which is about 32 x 31.5/22400 = 45mg (milligrammes). Assuming this 45mg can reach the surface of the beer by Brownian motion or small convection currents, it will struggle to venture deep into the beer, since it is more likely to set up a concentration gradient that works against it. And oxygen itself does not dissolve very well in aqueous solutions unlike CO2 which dissolves by forming carbonic acid in a reversible reaction.
If anyone disagrees with any of this please let us know. I have been known to get things wrong
Otherwise draw your own conclusions as to how real this problem actually is.

I cant disagree with what I don't understand! fair play...

foxbat · Jan 18, 2019

terrym said:
If you have a gas space above the beer in the FV of about 3 litres and it starts at 20*C and no more CO2 is being generated by fermentation and that is allowed to cool to 4*C two things can happen. A vacuum is drawn or gas is drawn in to maintain the pressure. If it is the latter the theoretical volume shrinkage from the original 3 litres is 3000 x 277/293 = 150ml approx. So there is a a potential to suck in 150 ml air. Since the oxygen concentration in air is about 21%v/v this equates to about 31ml of pure oxygen gas which is about 32 x 31.5/22400 = 45mg (milligrammes). Assuming this 45mg can reach the surface of the beer by Brownian motion or small convection currents, it will struggle to venture deep into the beer, since it is more likely to set up a concentration gradient that works against it. And oxygen itself does not dissolve very well in aqueous solutions unlike CO2 which dissolves by forming carbonic acid in a reversible reaction.
If anyone disagrees with any of this please let us know. I have been known to get things wrong
Otherwise draw your own conclusions as to how real this problem actually is.

Aren't you omitting brownian motion due to leaving the blow off tube open to the air during the whole time? I don't think the OP can leave the end dipped in starsan the whole time unless he has a tube long enough to not draw it back into the beer (my original suggestion of a long tube)

Bigcol49 · Jan 18, 2019

Tunabeast said:
quite like the idea of creating a positive pressure using CO2 but fear it would end up consuming quite a bit and running down my cylinder.

Hi!
One idea is to harvest the CO2 released during fermentation in a large balloon-type container which will be pulled back into the FV during cold crashing.
I wonder whether you could rig up a heavy-duty refuse bag to collect CO2?

Ajhutch · Jan 18, 2019

terrym said:
If you have a gas space above the beer in the FV of about 3 litres and it starts at 20*C and no more CO2 is being generated by fermentation and that is allowed to cool to 4*C two things can happen. A vacuum is drawn or gas is drawn in to maintain the pressure. If it is the latter the theoretical volume shrinkage from the original 3 litres is 3000 x 277/293 = 150ml approx. So there is a a potential to suck in 150 ml air. Since the oxygen concentration in air is about 21%v/v this equates to about 31ml of pure oxygen gas which is about 32 x 31.5/22400 = 45mg (milligrammes). Assuming this 45mg can reach the surface of the beer by Brownian motion or small convection currents, it will struggle to venture deep into the beer, since it is more likely to set up a concentration gradient that works against it. And oxygen itself does not dissolve very well in aqueous solutions unlike CO2 which dissolves by forming carbonic acid in a reversible reaction.
If anyone disagrees with any of this please let us know. I have been known to get things wrong
Otherwise draw your own conclusions as to how real this problem actually is.

Bravo for flipping the science versus anecdote argument around!

I can’t talk chemistry because frankly
I don’t knownit. I think it’s fair however to comment that chemically all beers are not equal. A brown ale or a stout or a Pilsner derives it’s flavour from different compounds than an IPA. And the compounds desirable in an IPA that’s had 25g/l of dry hops are both heavily concentrated (‘easy for oxygen to find’) and very volatile (‘easy for oxygen to destroy’). So it follows that what might be a perfectly acceptable risk in terms of oxygen contact for some beers isn’t for others.

Oxygen suckback during cold-crashing

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