Cold crash and oxidation

[archthered]

My 2 cents. You will definitely get some oxidation, if you are careful then the amounts will be low and likely make little immediate difference. However oxidization results in premature staling and the beer will not age as well as it could. I personally cold crash alot and have yet to notice any real issues with oxidization flavors, however I have not done any sensory panel stuff with oxidization and may not notice it at low levels, additionally I typically go through my beer fairly quickly so I usually don't have to worry about how well it ages, unless I'm doing a beer that needs to age. In short you are not wrong but they aren't wrong either, you will certainly get some oxygen in and it will alter the beer, but will it be enough that you personally should worry? Only you can tell, I'd try your beer and see what you think, think about the potential for oxidization flavors as you taste it and decide what you want to do in the future. Until then RDWHAHB

 

[yoop89]

With all due respect you are completely wrong on this one. Gasses mix

So, for you, "you are completely wrong" it's a normal explanation in a constructive conversation. Then okay

If you are referring to that post then yes, I believe that is constructive conversation. When someone says something that is blatantly incorrect I believe it is important to correct. This is a public forum that many people come to for information and if someone posts something that is wrong its important that it is corrected so others don't take it for truth.

 

[marchio-93]

If you are referring to that post then yes, I believe that is constructive conversation. When someone says something that is blatantly incorrect I believe it is important to correct. This is a public forum that many people come to for information and if someone posts something that is wrong its important that it is corrected so others don't take it for truth.

This sentence has been repeated a lot of time, and referring to something that is not incorrect at all. As someone said I pick up several litres of O2 but can not answer to the question "why not a single bubble in the airlock". So because it is a forum, maybe someone can read it and hear different opinion, and maybe DISCUSS, and don't put sentence as the truth. But if you want we can call this forum "ask to God the answer" and then just wait for your sentences.

Ps: I took a Belgian IPA to a competition, which was transfered and cold crashed for a week. It arrived on the podium, over counter-pressure beers. Maybe today send an email to the judges explaining why they are completely wrong

Pps: the beer was 4 months

 

[marchio-93]

My 2 cents. You will definitely get some oxidation, if you are careful then the amounts will be low and likely make little immediate difference. However oxidization results in premature staling and the beer will not age as well as it could. I personally cold crash alot and have yet to notice any real issues with oxidization flavors, however I have not done any sensory panel stuff with oxidization and may not notice it at low levels, additionally I typically go through my beer fairly quickly so I usually don't have to worry about how well it ages, unless I'm doing a beer that needs to age. In short you are not wrong but they aren't wrong either, you will certainly get some oxygen in and it will alter the beer, but will it be enough that you personally should worry? Only you can tell, I'd try your beer and see what you think, think about the potential for oxidization flavors as you taste it and decide what you want to do in the future. Until then RDWHAHB

Of course I will use the measures for the next cold crashes, thanks to the people who responded and gave me advice. I am very sorry for those who shoot sentences convinced that they have the truth in hand and have no intention of confronting each other

 

[yoop89]

Not sure what you're meaning by "not a single bubble in the airlock" but in your picture you can see all the liquid on the fermenter side of the airlock showing a vacuum has formed. Therefore, you possible got some air inside your fermenter. Whether or not you saw it happen is what it is. Congrats on the podium finish! Not a lot of people are dedicated enough to enter competitions.

Like others have said some people are super sensitive to oxidation flavors and some are not, some beers are more sensitive to O2 exposure, some less. Just take the last posters advice. RDWHAHB, we are all here for the same reason. Beer, right?

 

[marchio-93]

Not sure what you're meaning by "not a single bubble in the airlock" but in your picture you can see all the liquid on the fermenter side of the airlock showing a vacuum has formed. Therefore, you possible got some air inside your fermenter. Whether or not you saw it happen is what it is. Congrats on the podium finish! Not a lot of people are dedicated enough to enter competitions.

Like others have said some people are super sensitive to oxidation flavors and some are not, some beers are more sensitive to O2 exposure, some less. Just take the last posters advice. RDWHAHB

But when you ask to describe "oxidation", except for the heavily oxidated, thay can't! They give this name to anything is wrong with the beer as literally said by someone in this post. Excluding all the factors that come in brewing. That's incredible

 

[mkopec1]

Here is a link to anyone who wants to see for themself how gases mix.

Thanks for this. This basically proves that weve been sold a bunch of bullcrap about blankets of Co2 gently massaging our beer at all times, like I and im sure many of us have been taught by other homebrewers and even books and magazines.

 

[yoop89]

 

[lump42]

Thanks for this. This basically proves that weve been sold a bunch of bullcrap about blankets of Co2 gently massaging our beer at all times, like I and im sure many of us have been taught by other homebrewers and even books and magazines.

Yes, the 'co2 blanket' is an old brewer's tale. If it was true, we'd all be sitting in a sea of nitrogen since it is heavier than oxygen.

The counter point to the oxidation issue is that if you enjoy your beer the way you are brewing it now than it's the amount of oxidation isn't a flaw. I would still try and split a batch, half closed transfer and the other open, to see if there is a preference. That preference may change depending on style too.

 

[mediant]

This sentence has been repeated a lot of time, and referring to something that is not incorrect at all. As someone said I pick up several litres of O2 but can not answer to the question "why not a single bubble in the airlock".

Most likely you don't see the bubbles going back because it happens slowly behind the chiller's closed door.
I connect a urine bladder between the fermenter and the airlock to harvest CO2 for cold crash, and it decreases by 1-1.5 liters approximately while cold crashing, so I guess that's roughly the volume being sucked in.

 

[mkopec1]

Yes, the 'co2 blanket' is an old brewer's tale. If it was true, we'd all be sitting in a sea of nitrogen since it is heavier than oxygen.

The counter point to the oxidation issue is that if you enjoy your beer the way you are brewing it now than it's the amount of oxidation isn't a flaw. I would still try and split a batch, half closed transfer and the other open, to see if there is a preference. That preference may change depending on style too.

Problem with this is I dont have a sealed fermentor. Still using old school carboys I purchased in like the 90s. But even if I got one of those fermzillas or whatever how would you purge the O2 from the headspace on the fermentor? Even when the yeast is doing its thing and making Co2, there is still going to be O2 in the head space of the fermentor. Some of it will be pushed out by the spunding valve, but there will still be O2 in there, right? Or does the yeast eat up all the available O2, even in the head space?

 

[bob1852]

I think that's a bit exaggerated and simplistic, and of course not "the best way to discribe oxidation" but.. Okay

Why are you so defensive?

 

[lump42]

Problem with this is I dont have a sealed fermentor. Still using old school carboys I purchased in like the 90s. But even if I got one of those fermzillas or whatever how would you purge the O2 from the headspace on the fermentor? Even when the yeast is doing its thing and making Co2, there is still going to be O2 in the head space of the fermentor. Some of it will be pushed out by the spunding valve, but there will still be O2 in there, right? Or does the yeast eat up all the available O2, even in the head space?

You don't need a new fermentor. One of the orange carboy caps would be a cheap solution. The racking cane goes through one hole, co2 into the other.

The headspace almost entirely co2 at the tail-end of fermentation. The yeast will scavenge oxygen during their active phase. O2 in the lag phase is usually not an issue. The amount of co2 given off during the active fermentation will expel most of the rest. If you are using a stopper and airlock on a glass carboy that will keep o2 ingress into the headspace.

 

[lump42]

Problem with this is I dont have a sealed fermentor. Still using old school carboys I purchased in like the 90s. But even if I got one of those fermzillas or whatever how would you purge the O2 from the headspace on the fermentor? Even when the yeast is doing its thing and making Co2, there is still going to be O2 in the head space of the fermentor. Some of it will be pushed out by the spunding valve, but there will still be O2 in there, right? Or does the yeast eat up all the available O2, even in the head space?

Here's a video that lays out the steps. If you have a draft system, there wouldn't be much investment.

 

[marchio-93]

You don't need a new fermentor. One of the orange carboy caps would be a cheap solution. The racking cane goes through one hole, co2 into the other.

.

Okay thanks I've seen the video now. But what about a plastic bucket?

 

[mkopec1]

Hmm, this is giving me some ideas, guys, thanks. I wonder if I could make something like this to fit inside the carboy, maybe a ping pong ball? This would make the system even better by siphoning off the beer from the top not to disturb the trub and yeast on the bottom..

https://kegfactory.com/products/torpedo-keg-buoy™-floating-dip-tube

Or maybe its just time to retire the old tired glass carboys, lol.

 

[McKnuckle]

""why not a single bubble in the airlock"

During fermentation, CO2 inside the bucket is pushing outward through the airlock under pressure, venting to a practically infinite space at atmospheric pressure. The force from within the bucket causes visible and obvious bubbles in the airlock as the CO2 escapes. When the pressure equalizes between the bucket and the surrounding air, bubbling ceases.

During cold crash, an infinite volume of air at atmospheric pressure is drawn into a small volume of space (inside the bucket) by a vacuum, which it rapidly fills, causing only a few quick bubbles and then no more. Perhaps you just weren't watching when it happened?

 

[marchio-93]

During cold crash, an infinite volume of air at atmospheric pressure is drawn into a small volume of space (inside the bucket) by a vacuum, which it rapidly fills, causing only a few quick bubbles and then no more. Perhaps you just weren't watching when it happened?

Well I've followed all the fermentation, and I could clearly hear the bubbles of the Co2. As you say that the space is rapidly filled, so while I chill the fermenter I should hear or see this clear bubbling. This make me think that the only reason I don't hear or see any bubble is because the amount of O2 gone through the airlock is very little, and so I can not hear it. The amount of Co2 that get out during fermentation is not very huge, but you hear that sound for days.

 

[yoop89]

Most likely you don't see the bubbles going back because it happens slowly behind the chiller's closed door.
I connect a urine bladder between the fermenter and the airlock to harvest CO2 for cold crash, and it decreases by 1-1.5 liters approximately while cold crashing, so I guess that's roughly the volume being sucked in.

Well I've followed all the fermentation, and I could clearly hear the bubbles of the Co2. As you say that the space is rapidly filled, so while I chill the fermenter I should hear or see this clear bubbling. This make me think that the only reason I don't hear or see any bubble is because the amount of O2 gone through the airlock is very little, and so I can not hear it. The amount of Co2 that get out during fermentation is not very huge, but you hear that sound for days.

mediant says his fermenter draws back up to 1.5 litres? That seems like quite a bit when on average headspace is normally 4-5 litres. Also, cold crashing is a slow event, like others have said the "bubbles" of sucking back air happen slowly while the beer is cooling from your ferm temp to whatever you are crashing to.

 

[marchio-93]

mediant says his fermenter draws back up to 1.5 litres? That seems like quite a bit when on average headspace is normally 4-5 litres.

I've got 10 litres of headspace, that were full of Co2, before this stupid cold crashing

 

[marchio-93]

mediant says his fermenter draws back up to 1.5 litres? That seems like quite a bit when on average headspace is normally 4-5 litres. Also, cold crashing is a slow event, like others have said the "bubbles" of sucking back air happen slowly while the beer is cooling from your ferm temp to whatever you are crashing to.

And I add, I think it would be difficult to not hear 1.5 litres trough a 30 cc airlock

 

[yoop89]

If you would like to visually monitor how much suckback you get during cold crash you could buy or build something like this. Hook it up for fermentation and watch how much sanitizer/co2 is pulled back.

https://www.norcalbrewingsolutions.com/store/CO2-Carbon-Dioxide-Harvester-Kit.html

I was considering something like this but just stopped cold crashing.

 

[McKnuckle]

...the only reason I don't hear or see any bubble is because the amount of O2 gone through the airlock is very little, and so I can not hear it. The amount of Co2 that get out during fermentation is not very huge, but you hear that sound for days.

Actually the amount of CO2 leaving during fermentation is pretty large (gallons worth), and it's pressurized with respect to the atmosphere around it. So the force of leaving the bucket through the airlock causes obvious bubbling.

In contrast, the amount of air entering during cold crash is only enough to fill the head space at atmospheric pressure, and it is probably drawn in slowly (I'll correct my post above), which is why it's not as easy to see.

I haven't cold crashed with an airlock in a long time, but when I did, I never saw the ingress of air, BUT I could tell that it happened, because the airlock liquid became visibly depleted.

 

[marchio-93]

If you would like to visually monitor how much suckback you get during cold crash you could buy or build something like this. Hook it up for fermentation and watch how much sanitizer/co2 is pulled back.

https://www.norcalbrewingsolutions.com/store/CO2-Carbon-Dioxide-Harvester-Kit.html

I was considering something like this but just stopped cold crashing.

Thanks! I think I'll start with a balloon and watch what happen

 

[yoop89]

And I add, I think it would be difficult to not hear 1.5 litres trough a 30 cc airlock

Are you inside the fermenter? The noise of a bubble is caused on the surface of the liquid it is breaking. When drawing air back in that surface is now inside a bucket insulating it ever so slightly. I guarantee it bubbled albeit very slowly so possible you just didnt "catch" one?

 

[RPh_Guy]

Sorry double post

 

[RPh_Guy]

Here is a link to anyone who wants to see for themself how gases mix.

It says exactly that if a gas it's heavier than another it takes a lot of time to mix

In the clip, the Br2 and "air" is fully mixed after just half an hour. Br2 is about 4 times as heavy as C02.

It was implied here that CO2 diffusion is faster because Graham's Law states that the diffusion rate is inversely proportional to the square root of the mass of the molecule. Also notice that the mixing starts immediately and the initial rate of mixing near the interface is (exponentially) higher because of the higher concentration gradient.
The physics of gas movement is well understood.

Of further interest, during a cold crash two processes are occurring:
1. Thermal contraction of the liquid and gas in the headspace. This is more than enough to pull in too much oxygen in its own right, and the amount of air pulled in can be easily calculated using the ideal gas law.
2. The solubility of carbon dioxide increases, so a lot of the gas in the headspace gets absorbed into the beer. This process pulls in the majority of the outside air.

It's a scientific fact that air is being pulled into a fermenter when the temperature drops significantly, when there is only a fluid-filled airlock.

I can not hear people say "you completely wrong" or things like that, to other people, as they have the truth in their hand, when their is nothing more approximate than our hobby. Maybe to justify thousands of dollars' worth of equipment, and then repeat the same sentence without giving a real scientific answer

I know you're not referring to me because the first thing I suggested was spunding instead of cold crashing.
Spunding is the ultimate way to reduce cold side oxidation.

Please be respectful when people are putting out information to help answer your questions. We are all trying to help.

 

[mkopec1]

What do you mean by spunding instead of cold crashing? Dont do cold crashing? Im not sure I understand.

 

[marchio-93]

In the video there is a small amount of gas, I had 10 litres of Co2 in my fermenter, so cold crashing in some days, not in one minute, I think my headspace is not full of 02 in few seconds as you said.

The only one who did not respect other people opinions was you, because you did not just put some notions in those posts, but you said other people were completely wrong and saying cold crash 02 would STRONGLY affect the beer, so I repeat to you maybe email the judges of the Belgian IPA, heavely hopped, and say them to change their hobby/job

 

[RPh_Guy]

What do you mean by spunding instead of cold crashing? Dont do cold crashing? Im not sure I understand.

Yes, that is what I'm recommending.
Actively fermenting yeast protect beer from oxidation by rapidly absorbing any dissolved oxygen.
The longer the beer sits after fermentation ends, the more oxygen exposure occurs.

In the video there is a small amount of gas, I had 10 litres of Co2 in my fermenter, so cold crashing in some days, not in one minute, I think my headspace is not full of 02 in few seconds as you said.

Mixing of gases occurs fast enough that there is no such thing as a CO2 blanket, even during active fermentation. This is based on the science of gas physics.

Air is drawn into your fermenter over a period of hours-days. The headspace mixes relatively rapidly. Oxygen in the headspace forms an equilibrium with some of it dissolving in the beer. Oxygen radical species from dissolved oxygen are what causes the "oxidation" changes in flavors. Since the dissolved oxygen is consumed by these reactions, Le Chatelier's principle dictates that even more oxygen will dissolve into the beer to maintain equilibrium.

The only one who did not respect other people opinions was you, because you did not just put some notions in those posts, but you said other people were completely wrong and saying cold crash 02 would STRONGLY affect the beer, so I repeat to you maybe email the judges of the Belgian IPA, heavely hopped, and say them to change their hobby/job

This is what I said:

To my taste, yes, strongly.

I chose my words carefully since everyone has different tastes.

 

[Robert65]

It seems to me that the exact amount of oxygen drawn into the headspace (and ultimately dissolved in the beer) during a conventional cold crash is unimportant. Whatever the amount, it will be measured in percent, parts per hundred. Meanwhile, the maximum tolerable amount of oxygen exposure for beer after active fermentation has abated, to avoid noticeable, damaging oxidation, is measured in parts per billion. So it is advisable to do whatever we can to avoid oxygen ingress.

Spunding really is the ultimate solution for homebrewers. This means transferring the beer from the fermenter to the keg -- a closed transfer to avoid as much risk as possible -- when there is still just enough fermentation left to go to naturally carbonate the beer. The benefits include that active fermentation will scavenge the small amount of oxygen inevitably picked up even in a closed transfer, and you will have fully carbonated beer by the time it reaches FG without the need for force carbonation with gas that costs good money (and is not nearly as pure as fermentation generated CO2.) Then you can cold crash the keg to clear the beer for serving. This also obviously greatly reduces turnaround time for the batch.

 

[marchio-93]

This is what I said:

I chose my words carefully since everyone has different tastes.

You don't know the kind of beer, how long I've cold crashed but you know it will strongly affected by oxidation. Okay. When, apart from the long-term loss of characteristics (and my beers are mostly finished in two months) you cannot describe it in any other way. Great

 

[marchio-93]

, and you will have fully carbonated beer by the time it reaches FG without the need for force carbonation with gas that costs good money (and is not nearly as pure as fermentation generated CO2.)

Thanks! But I don't get this part. Do you calculate the carbonation you get in your beer by the eaten point of gravity?

And do you dry hop directly in your keg?

 

[Robert65]

Thanks! But I don't get this part. Do you calculate the carbonation you get in your beer by the eaten point of gravity?

There are other threads on the forum going into much more detail on spunding. But in short:

You will want to have an idea of what the final gravity of your beer will be. The best way to determine this is a forced fermentation test (FFT,) but experience may be a guide.

Then you may want to account for the amount of CO2 dissolved in beer depending on temperature: a cold fermented lager will have more than a warm fermented ale.

You will then transfer the beer at 0.5-1°P or 0.002-0.004 specific gravity above final.

Finally, most people use a spunding valve, a variable pressure relief valve with a pressure gauge to monitor pressure, to make sure any excess is vented, setting the pressure based on the usual charts showing volumes of CO2 against temperature and pressure.

It is also possible to apply the principle in bottling, but that requires greater precision since you'll have no relief valve, and it's not something I have done myself.

 

[RPh_Guy]

Oxidation affects all beers because all beers contain compounds that will react with dissolved oxygen.
These reactions occur over days to weeks at typical temperatures at which beer is stored.

While different styles of beer can respond differently, oxidation generally results in the muting of desirable hop and malt characteristics, creates a more harsh bitterness, caramel notes, catty and grassy notes from hops, and at some point papery/cardboard flavors. It's a complex process, so any answer in a forum post is going to be an over-simplification. I personally don't like the effects of oxidation and taste them quite readily.

Ultimately what matters is whether you're happy with your beer.
The science of these chemical reactions and physical processes is factual and unbiased. However what you choose to do with the information is up to you and your tastes and brewing goals.

Cheers

 

[marchio-93]

Ultimately what matters is whether you're happy with your beer.

Of course.
And if you can taste too caramel or harshness and say it comes from O2 and not from ph, dry hopping, and other billions of reasons then congrats!

 

[mkopec1]

There are other threads on the forum going into much more detail on spunding. But in short:

You will want to have an idea of what the final gravity of your beer will be. The best way to determine this is a forced fermentation test (FFT,) but experience may be a guide.

Then you may want to account for the amount of CO2 dissolved in beer depending on temperature: a cold fermented lager will have more than a warm fermented ale.

You will then transfer the beer at 0.5-1°P or 0.002-0.004 specific gravity above final.

Finally, most people use a spunding valve, a variable pressure relief valve with a pressure gauge to monitor pressure, to make sure any excess is vented, setting the pressure based on the usual charts showing volumes of CO2 against temperature and pressure.

It is also possible to apply the principle in bottling, but that requires greater precision since you'll have no relief valve, and it's not something I have done myself.

I see now, but with a fully closed system like you propose, how do you test gravity before you rack into keg? It would seem that any test like this would inevitably introduce O2.

 

[lump42]

Okay thanks I've seen the video now. But what about a plastic bucket?

The easiest procedure would be to install a spigot on the bottom and attach the keg gas post back to the airlock. While the keg fills with beer, the CO2 from the keg is pushed out the gas post, which has tubing connected to the airlock stem on the bucket lid. The bucket headspace fills with CO2 from the keg as the beer level drops. The beer fermentor and the co2 in the keg swap places.

It would be similar to this video but with a plastic bucket and a spigot.

 

[Robert65]

I see now, but with a fully closed system like you propose, how do you test gravity before you rack into keg? It would seem that any test like this would inevitably introduce O2.

I ferment in a pressure capable fermenter (a modified 10 gallon corny.) So I just put gas on the in port and use a picnic tap to take a sample from my floating dip tube. (I also have a spear tube for pulling slurry, but that's another story...) Something like this can be improvised with most fermenters, as long as you can put gas in to replace the volume coming out. You obviously have to be able to do this to do a closed transfer anyway, so it should already be arranged.

 

[RPh_Guy]

I see now, but with a fully closed system like you propose, how do you test gravity before you rack into keg?

In any fermentation vessel with a spigot you can drain out beer slowly while keeping an eye on the airlock. CO2 production from active fermentation continually replaces the beer being drained, so no air will be pulled in if you're careful. Make sure the airlock is full so there's some leeway.
Same goes if using a blow-off tube; keep an eye on the solution in the blow-off container (or tubing if you're using something see-though).

Using a refractometer instead of a hydrometer to compare it to the FFT reduces the amount of beer you need to sample for monitoring purposes.