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Cold Crashing and Oxygen

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BolgBeorach

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I realise that this question has been asked before, but I'm none the wiser from reading the older threads. Does cold crashing actually increase the risk of oxidation in a substantial way? I have seen posts stating that the suckback from the contracting liquid/air inside the fermentor would introduce oxygen via the airlock and thus probably cause oxidation of the beer; but doesn't oxygen enter anyway when we open it to take a hydrometer reading or to dry hop? And the amount that might enter the vessel through the airlock due to temperature change must surely be far less than that introduced when taking the whole lid off and putting something into the beer. Has anyone here experienced significant oxidation attributable to cold crashing?
 

eric19312

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Yes all of those things let oxygen into the fermentor. Oxygen on cold side is additive. A little bit from here plus a little bit from there and you have enough to cause a problem. The threshold where a problem develops is surprisingly low. The problem appears to be really noticeable in modern light colored fruity juicy IPAs. Commercial brewers target dissolved oxygen concentration in finished beer (Total Package Oxygen) below about 100 parts per billion.
 
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BolgBeorach

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Yes all of those things let oxygen into the fermentor. Oxygen on cold side is additive. A little bit from here plus a little bit from there and you have enough to cause a problem. The threshold where a problem develops is surprisingly low. The problem appears to be really noticeable in modern light colored fruity juicy IPAs. Commercial brewers target dissolved oxygen concentration in finished beer (Total Package Oxygen) below about 100 parts per billion.
Interesting. Would the headspace in the fermentor make a difference to oxygen exposure, do you reckon? Right now, I have 11 litres of pale ale in a 22 litre fermentor, and the only time that it will have had oxygen possibly enter is while I cold crash. I dry hopped by dropping the pellets in through the airlock aperture. I imagine if there is a large headspace of CO2, the the O2 that diffuses in through the airlock might have minimal contact with the beer
 

VikeMan

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I imagine if there is a large headspace of CO2, the the O2 that diffuses in through the airlock might have minimal contact with the beer
That's the "CO2 Blanket" theory, which doesn't stand up to scrutiny.
Here's why:
The video shows Bromine, which is even heavier than CO2.
 

eric19312

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That is a huge headspace. When you open the fermentor the oxygen in the air will diffuse into that headspace due to the difference in concentration of Oxygen in the headspace vs the atmosphere. The greater the concentration difference the greater the force compelling the oxygen molecules to move into the headspace to try to equalize the concentration gradient.
 

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I've drilled a 1" access hole (to hold a 1" rubber carboy stopper) in my bucket lids, opposite from the airlock hole. I blow CO2 in at around 10-15 psi through the (3-piece) airlock stem (or through a hose stuck inside the airlock hole), while adding dry hops or stirring them through the 1" access hole.

When cold crashing I use a mylar balloon filled with CO2 attached to the airlock stem to prevent air from entering during contraction. It's not just the liquid that contracts when lowering temps, gases do too, and more so.
 
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BolgBeorach

BolgBeorach

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That's the "CO2 Blanket" theory, which doesn't stand up to scrutiny.
Here's why:
The video shows Bromine, which is even heavier than CO2.
I was more thinking that the large amount of CO2 in a bigger headspace might mean that the oxygen that did manage to enter via suckback would be more diluted, compared to a case in which the headspace was smaller and the O2 that entered would thus constitute a higher percentage of the gas in the headspace.
 

VikeMan

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I was more thinking that the large amount of CO2 in a bigger headspace might mean that the oxygen that did manage to enter via suckback would be more diluted, compared to a case in which the headspace was smaller and the O2 that entered would thus constitute a higher percentage of the gas in the headspace.
At the end of the day, the concentration of CO2 doesn't matter vis a vis O2. They each seek equilibrium between the headspace and the beer independently, i.e. according to their own partial pressures. (See Henry's law.)

It's true that if "X" mass of O2 gets into a small headspace and "X" O2 also gets into a large headspace, its concentration will be lower in the larger headspace, and so the equilibrium state in that fermenter will result in less O2 in the beer. But any O2 getting to the beer is not a good thing. A large headspace won't eliminate the problem.
 

renstyle

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Does cold crashing actually increase the risk of oxidation in a substantial way? I have seen posts stating that the suckback from the contracting liquid/air inside the fermentor would introduce oxygen via the airlock and thus probably cause oxidation of the beer; but doesn't oxygen enter anyway when we open it to take a hydrometer reading or to dry hop? And the amount that might enter the vessel through the airlock due to temperature change must surely be far less than that introduced when taking the whole lid off and putting something into the beer. Has anyone here experienced significant oxidation attributable to cold crashing?
Cold crashing in and of itself does nothing for O2 ingress...

Cold crashing while utilizing the standard airlock/blowoff is where you run into problems. The idea is to accept that Boyle's law is going to act upon free-flowing gasses as temps fluctuate, so mitigate that effect...

@IslandLizard mentioned using a mylar balloon filled with CO2 to supplant the airlock and let Boyle's law suck CO2 back into the fermenter while crashing.

For mitigation during dry hopping, in addition to the suggestions above, you could time your DH addition while primary fermentation is still ongoing, even if you pump additional CO2 into the fermenter while it's open.

If the yeast are still active, they will chew thru most (all?) of the O2 still in the fermenter that entered during the addition. (Wiser folks, feel free to correct me on this point if needed).
 

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I've used the mylar balloon rig, and I was surprised how much air got sucked back into the fermenter, more than a quart. Will your beer be exposed to oxygen? Yes. Will it make a difference or will you notice? Hard to say, depends on the beer, time and temperature I suppose. I now transfer to a keg with a spunding valve before it is finished and no longer have to worry about suckback.
 

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I've used the mylar balloon rig, and I was surprised how much air got sucked back into the fermenter, more than a quart. Will your beer be exposed to oxygen? Yes. Will it make a difference or will you notice? Hard to say, depends on the beer, time and temperature I suppose. I now transfer to a keg with a spunding valve before it is finished and no longer have to worry about suckback.
In your experience, is there a minimum threshold of positive pressure the spunding valve needs to maintain such that during cold crashing the pressure is high enough in the keg to not break the lid seal due to excess negative pressure?
 

VikeMan

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If the yeast are still active, they will chew thru most (all?) of the O2 still in the fermenter that entered during the addition. (Wiser folks, feel free to correct me on this point if needed).
I think the yeast will use some O2, but not much. The main use for O2 is to build sterols for cell walls prior to budding. Toward the end of fermentation, the yeast aren't gearing up for cell division.

I believe this is also the reason why bottle carbonating doesn't get rid of all the O2 in the headspace as it diffuses into the beer, and breweries like Bells (who bottle prime) go to great lengths to purge the O2 from their bottles.
 

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In your experience, is there a minimum threshold of positive pressure the spunding valve needs to maintain such that during cold crashing the pressure is high enough in the keg to not break the lid seal due to excess negative pressure?
Probably, but I've never set the pressure low enough to see it happen. When I put the valve on I'll charge the keg with about 10 psi to make sure the lid is seated tight, with the valve tightened up about all the way. After the pressure builds I'll loosen it to set the valve for 30 psi at 66F. When I cold crash the pressure drops to about 10-12.
 
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BolgBeorach

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At the end of the day, the concentration of CO2 doesn't matter vis a vis O2. They each seek equilibrium between the headspace and the beer independently, i.e. according to their own partial pressures. (See Henry's law.)

It's true that if "X" mass of O2 gets into a small headspace and "X" O2 also gets into a large headspace, its concentration will be lower in the larger headspace, and so the equilibrium state in that fermenter will result in less O2 in the beer. But any O2 getting to the beer is not a good thing. A large headspace won't eliminate the problem.
I get what you mean. Thanks for the detailed replies! Does it make a difference if the O2 exposure is over a very limited time frame? I'm only planning on cold crashing 24 hours before bottling, so I guess it won't be sitting there for a long time with a potentially O2-laced headspace. I'm guessing the process of transferring it to the bottling bucket will probably cause way more oxygen exposure even without splashing
 

renstyle

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I get what you mean. Thanks for the detailed replies! Does it make a difference if the O2 exposure is over a very limited time frame? I'm only planning on cold crashing 24 hours before bottling, so I guess it won't be sitting there for a long time with a potentially O2-laced headspace. I'm guessing the process of transferring it to the bottling bucket will probably cause way more oxygen exposure even without splashing
The priming sugar you add to either the bottling bucket, or to the individual bottles would clear much of the O2 that gets trapped in the bottles during packaging.

I'm unsure how the previous 24hr period of cold crashing would affect the priming sugar's ability to clear the O2 tho.
 

VikeMan

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Does it make a difference if the O2 exposure is over a very limited time frame? I'm only planning on cold crashing 24 hours before bottling, so I guess it won't be sitting there for a long time with a potentially O2-laced headspace. I'm guessing the process of transferring it to the bottling bucket will probably cause way more oxygen exposure even without splashing
I don't have solid numbers on which will result in more dissolved O2.

I'm unsure how the previous 24hr period of cold crashing would affect the priming sugar's ability to clear the O2 tho.
"A lot" (a little O2 is a lot when talking about oxidation) of that O2 from cold crash suck back will have already oxidized compounds in the beer and wouldn't be available to the yeast even if the yeast wanted all of it.
 

renstyle

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I've seen others utilize a "double blowoff" during cold crashing to eliminate O2 ingress as well.

Daisy-chain two closed vessels. Blow off tube into vessel #1 which is filled with sanitizer (tho technically any airlock-friendly fluid would be OK here).

Use fermentation gas to push this sanitizer into a 2nd holding vessel and maintain the airlock. the 2nd vessel isn't sealed so it does the bubbling....

When you cold crash, the fermentation gas, which is nearly pure CO2, gets sucked back into the fermenter. The airlock is maintained by the sanitizer migrating back into the initial vessel it started in.

It's basically a convoluted system that gets you to the same place as replacing the airlock with the CO2-filled mylar balloon.

It has the advantage of setting it up at the beginning (or mid-way) of fermentation and letting it roll until you hit FG (provided you have a holding vessel large enough to keep the StarSan foam at bay) LOL

Basically this:


1603147867167.png
 

day_trippr

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I ferment 5.5 gallons in 6.5 gallon carboys. I doubt those jars would hold enough CO2 from fermentation to supply the "suck-back" volume without O2 entering the equation (that entire rig will flow in reverse pulling in outside air)...

Cheers!
 

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I've used the mylar balloon rig, and I was surprised how much air got sucked back into the fermenter, more than a quart.
Why did you have the balloon filled with air?
It should be filled with CO2, to prevent sucking in air instead.

Now the fermenter needs to have a decent seal, or air may get sucked in along any leaks in the closure.
 

Qhrumphf

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A) initial oxidation reactions happen quite quickly (though not necessarily the entire chain of reactions). With a sensitive enough meter (not affordable at home) you can essentially watch this happen. 24 hrs later the dissolved oxygen is for the most part taken up and the damage is done.

B) unless initial fermentation is still active, from what I can garner the limited activity of yeast consuming priming sugar is marginally effective at best at scrubbing out DO.
 

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Why did you have the balloon filled with air?
It should be filled with CO2, to prevent sucking in air instead.

Now the fermenter needs to have a decent seal, or air may get sucked in along any leaks in the closure.
By 'air' I meant CO2 from fermentation. Here is a picture of the setup. I used one of the tube clips to keep the balloon closed until fermentation was well underway.
003 (2).JPG
 

EDF713

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Yeah, I hoped that's what you meant. :D

That's a good setup you got there. ^ Simple and efficient!
That balloon, as long as it's not empty, should also prevent suck back from that blow-off jug.
Since I've started spunding I don't use it anymore, but it was a fun little project. I bought a cheap T at Home Depot and the ballon at the dollar store, and had everything else like the tubing already. It worked marvelously to keep O2 out, except for when I would open the whole thing up to siphon into the keg...
 

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@IslandLizard and @EDF713 Did you ever get any funky flavors from the mylar balloon post coldcrash? I’m going to do something like this with my next batch but was planning on using a liquid catch bag from a medical supply company. However mylar balloons are much easier and cheaper to source.
 

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Another way to look at it is that I've already ruined a few batches while having my own DIY fun. For example, finding out that medical catch bags have one way valves in them that prevented the CO2 from going back in as intended..
 

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Those carboy caps allow you to easily do a pressure/closed transfer with a racking cane and some CO2. I'm surprised you didn't use it to your advantage.
I am too, I didn't think of it until I switched to spunding and taking cold side oxidation more seriously. I've thought of it since, I have an old racking cane I don't use any more. Now I'm either spunding early or using a tall pinlock to ferment in if it's a lager. I may try it, sometimes I wonder if siphoning to my spunding keg is still introducing too much O2.
 

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Both kits are good deals, it's worth it just not having to round up the parts if you don't have them.
 

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@IslandLizard and @EDF713 Did you ever get any funky flavors from the mylar balloon post coldcrash? I’m going to do something like this with my next batch but was planning on using a liquid catch bag from a medical supply company. However mylar balloons are much easier and cheaper to source.
I never noticed a problem. If you get a normal sized balloon it doesn't such back the whole volume.
 

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@IslandLizard and @EDF713 Did you ever get any funky flavors from the mylar balloon post coldcrash? I’m going to do something like this with my next batch but was planning on using a liquid catch bag from a medical supply company. However mylar balloons are much easier and cheaper to source.
I've read about wicked aromas inside those balloons. Maybe from the printing inks?
Can it be flushed out with fermentation CO2?

I'm using a mylar bag that contained hops. ;)
 

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I ferment 5.5 gallons in 6.5 gallon carboys. I doubt those jars would hold enough CO2 from fermentation to supply the "suck-back" volume without O2 entering the equation (that entire rig will flow in reverse pulling in outside air)...

Cheers!
I agree, the jars in the pic/link are on the small side. I was just trying to include a visual to accompany my text to illustrate the idea I was positing 😉
 

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I have the cold crash guardian. Only used it once so far, seems to work as advertised.
 

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I've read about wicked aromas inside those balloons. Maybe from the printing inks?
Can it be flushed out with fermentation CO2?

I'm using a mylar bag that contained hops. ;)
Hop aroma CO2 bags for *extra* aroma. This sounds like a product waiting to happen.
I’ve read the same comments which makes me wonder if its a wise thing to do. Seems as though plenty of people have done it with no ill effects though. Crash guardian sounds like a safer bet.
 

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I use a blow off tube with a syphon tap halfway along. When i crash i turn off the tap and it will suck the lid in a little. Obviously i am using buckets.
 

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I use a blow off tube with a syphon tap halfway along. When i crash i turn off the tap and it will suck the lid in a little. Obviously i am using buckets.
Buckets are notorious for leaking at the huge lid seal. If the lid only sucks in a little, you are very likely getting some gas sucked in.
 

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Buckets are notorious for leaking at the huge lid seal. If the lid only sucks in a little, you are very likely getting some gas sucked in.
Hi Bobby, My buckets are fairly robust but i know what you mean. Would like to buy one of your guardians if you ship to the UK?
 
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