Hop stability- Bottling vs kegging

[BamaPhil]

So I brewed a hoppy amber that has previously won a medal with a 41, all judges agreed the hop flavor and aroma were on point. The bottles I entered were a few months old at least, although stored in the fridge.

Flash forward a year and half, and I've graduated to kegging. Since that beer was so well received, I brewed it to supply my 3rd and final tap. After a week and a half or so in the keg, it was shaping up nicely.

A week or two later though, and all the hops are GONE. It honestly tastes just like my ESB that seems to have gone through the same problem.

I know, it's probably oxygen. BUT, is oxygen that much more of a threat to a kegged beer than a bottled one? I know the yeast theoretically take in the O2 during bottle conditioning, but dang this was a dramatic difference.

Has anyone else ever had this problem? I purged the keg with CO2 before transferring, which is something I obviously couldn't do when bottle conditioning. It just seems to me the oxidation shouldn't be THAT much worse when kegging, especially since the temperature has been no greater than 40F since fermentation.

 

[beskone]

How did you purge?

You have to purge at least 10 - 12 times @ 30psi to eliminate most of the O2 in the headspace of a keg.

I have an IPA that the hops faded pretty quickly (3-4 weeks) I wasn't paying attention and purged the keg 10 times at 10psi, likely leaving enough O2 to cause the loss of the hop aromas / flavor. I'll be re-dry hopping this one in the keg this weekend to freshen it up.

When you bottle condition headspace O2 is less of a concern as the yeast will use up the O2 and replace with CO2.

 

[BamaPhil]

I filled the keg with CO2 under serving pressure (11 psi). I basically just verified this by sticking a lighter into the keg to make sure it went out at the opening, haha.

By "purge 10 times" what process are you talking about? Apply gas, shut it off, vent, repeat? After 10 times you remove the lid and rack the beer?

 

[beskone]

Once you've gotten the beer into the keg, seal it up and turn pressure up to 30psi, vent, repeat 10-15 times.

If you pre-pruge the keg, that's not really getting rid of all the O2. that's just mixing a bunch of CO2 into the keg, then letting O2 mix back in from the air.

Here's a chart showing CO2 levels in the headspace with different pressures and number of purges.

My normal process is, Fill keg with 5 gallons of Star San. When it's time to keg I push all the starsan out of the keg with CO2 into a clean empty keg.

I then force transfer from my carboy to the liquid out post on the keg with the pressure relief valve open. Once full, close PRV, pressure to 30psi, vent, repeat.

 

[fun4stuff]

Once you've gotten the beer into the keg, seal it up and turn pressure up to 30psi, vent, repeat 10-15 times.

If you pre-pruge the keg, that's not really getting rid of all the O2. that's just mixing a bunch of CO2 into the keg, then letting O2 mix back in from the air.

Here's a chart showing CO2 levels in the headspace with different pressures and number of purges.

My normal process is, Fill keg with 5 gallons of Star San. When it's time to keg I push all the starsan out of the keg with CO2 into a clean empty keg.

I then force transfer from my carboy to the liquid out post on the keg with the pressure relief valve open. Once full, close PRV, pressure to 30psi, vent, repeat.

Is this really needed? How many people do this? I've just been using a sterile siphon to transfer from carboy to keg out post. Then will purge with CO2 3-4 seconds, 3-4 times. Haven't noticed any oxidation, even after months in keg.

 

[day_trippr]

Is this really needed? How many people do this? [...]

Yo! [hand raised]

Or close enough: I always have 5 gallons of Star San on hand and I'd been doing CO2-push FV-keg transfers anyway, so it was no big deal to fill the keg with Star San, seal it up, do a CO2-push back to the Star San reservoir, then do the CO2-push from the fermenter (which was cold-crashed under CO2 as well).

Yes, that's called "obsession"

But I maintain a pipeline towards six faucets and typically have six kegs cold-carbing/conditioning as they await their turn in the keezer, and I don't want to lose all the volatile characters before they even get tapped...

Cheers!

 

[BamaPhil]

Once you've gotten the beer into the keg, seal it up and turn pressure up to 30psi, vent, repeat 10-15 times.

If you pre-pruge the keg, that's not really getting rid of all the O2. that's just mixing a bunch of CO2 into the keg, then letting O2 mix back in from the air.

Here's a chart showing CO2 levels in the headspace with different pressures and number of purges.

[...]

I then force transfer from my carboy to the liquid out post on the keg with the pressure relief valve open. Once full, close PRV, pressure to 30psi, vent, repeat.

That's good info, thanks!

Is this really needed? How many people do this? I've just been using a sterile siphon to transfer from carboy to keg out post. Then will purge with CO2 3-4 seconds, 3-4 times. Haven't noticed any oxidation, even after months in keg.

I suspect that this, like SO many other things, isn't really needed. Its just a matter of how obsessive you want to be and over what particular details.

Yo! [hand raised]

Or close enough: I always have 5 gallons of Star San on hand and I'd been doing CO2-push FV-keg transfers anyway, so it was no big deal to fill the keg with Star San, seal it up, do a CO2-push back to the Star San reservoir, then do the CO2-push from the fermenter (which was cold-crashed under CO2 as well).

Yes, that's called "obsession"

But I maintain a pipeline towards six faucets and typically have six kegs cold-carbing/conditioning as they await their turn in the keezer, and I don't want to lose all the volatile characters before they even get tapped...

Cheers!

I've read about pushing star-san out with CO2 but that seems like it would use up your CO2 really fast. Do you guys find that to be the case?

What are you using to push the beer from the carboy? I'm guessing some kind of cap with a ball lock post on it?

 

[day_trippr]

[...]
I've read about pushing star-san out with CO2 but that seems like it would use up your CO2 really fast. Do you guys find that to be the case?

What are you using to push the beer from the carboy? I'm guessing some kind of cap with a ball lock post on it?

Exactly. It's quite handy to have...









Cheers!

 

[303Dan]

Is this really needed? How many people do this? I've just been using a sterile siphon to transfer from carboy to keg out post. Then will purge with CO2 3-4 seconds, 3-4 times. Haven't noticed any oxidation, even after months in keg.

I'm doing the purging part (13 purges @ 30 psi). I actually have noticed a difference from when I was doing just a few purges @ 10 psi. Once I can, I'll be adding the ability to do closed transfers. And yes, I am obsessive.

 

[doug293cz]

Is this really needed? How many people do this? I've just been using a sterile siphon to transfer from carboy to keg out post. Then will purge with CO2 3-4 seconds, 3-4 times. Haven't noticed any oxidation, even after months in keg.

To protect an oxidation sensitive beer like an IPA, yes it is required. Look at page 21 of this presentation: http://www.craftbrewersconference.com/wp-content/uploads/2015_presentations/F1540_Darron_Welch.pdf. 0.15 ppm of total packaged oxygen (TPO) was enough to affect the flavor of an IPA in a few weeks. To calculate the contribution to TPO from the headspace O2, use the following formula:

TPO Contribution = Headspace Vol * Headspace O2 ppm / (Headspace Vol + Beer Vol)​

To get the beer's contribution to TPO, you need to get a dissolved oxygen (DO) meter, and these are not cheap.

Your practice of letting the CO2 flow during the vent part of the keg purge cycle will get out more O2 per cycle than shutting off the supply during venting. The problem is that it's not possible (in the general case) to calculate how much more effective the "flowing vent" will be vs. the static vent. I am the creator of the residual O2 chart posted above, and doing "flowing vent" calculations for even an over simplified set of conditions is beyond my ability,

With your method, you have no clue what your residual O2 level is after you purge. Do you want to bet the longevity of your beer on an unknown O2 level?

Brew on

 

[fun4stuff]

To protect an oxidation sensitive beer like an IPA, yes it is required. Look at page 21 of this presentation: http://www.craftbrewersconference.com/wp-content/uploads/2015_presentations/F1540_Darron_Welch.pdf. 0.15 ppm of total packaged oxygen (TPO) was enough to affect the flavor of an IPA in a few weeks. To calculate the contribution to TPO from the headspace O2, use the following formula:

TPO Contribution = Headspace Vol * Headspace O2 ppm / (Headspace Vol + Beer Vol)​

To get the beer's contribution to TPO, you need to get a dissolved oxygen (DO) meter, and these are not cheap.

Your practice of letting the CO2 flow during the vent part of the keg purge cycle will get out more O2 per cycle than shutting off the supply during venting. The problem is that it's not possible (in the general case) to calculate how much more effective the "flowing vent" will be vs. the static vent. I am the creator of the residual O2 chart posted above, and doing "flowing vent" calculations for even an over simplified set of conditions is beyond my ability,

With your method, you have no clue what your residual O2 level is after you purge. Do you want to bet the longevity of your beer on an unknown O2 level?

Brew on

It mentions 4 months with "cold" storage. Probably why the taste difference isn't really noticable at homebrew scale. Anyways, doesn't sound like one can really estimate TPO without a DO meter. So any number of purges is more of a guesstimate. Of course closed transfers would be optimal.... Assuming you have some way checking sg and dry hopping without opening fermentor. That's a lot of co2 though....at least 30% of a 5 lb tank just to transfer? Might as well buy a dedicated 10+ lb tank just for transfers. I don't know if there's a point if you can't tell a difference in taste though, assuming beer will be drank within a couple months and kept cold. I'm just trying to separate homebrew myth from good practice: so many of these recommendations from the commercial industry don't lead to significant difference in taste at homebrew scale.

 

[khillian]

I was going by the math in this post, https://www.homebrewersassociation.org/forum/index.php?topic=15079.msg191470#msg191470

I normally vent the head space after filling with beer 5x at 30psi. It has been working well for me, my hoppy beer rarely lasts over a month. Ones that I have bottled off the keg sitting for a month got 41s recently in World Cup of Beer. Is doing another 5 purges that big of a difference? Are you a c02 supplier ?

 

[beskone]

Hmmm, you're setup looks familiar! Guess we're both members of the minimal O2 exposure crew.

Exactly. It's quite handy to have...

View attachment 353763

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Cheers!

 

[fun4stuff]

Hmmm, you're setup looks familiar! Guess we're both members of the minimal O2 exposure crew.

At what point do you put the balloon on? How do you prevent air from getting in when you dry hop?

 

[beskone]

At what point do you put the balloon on? How do you prevent air from getting in when you dry hop?

You can't completely avoid exposing it to the air. We're trying to *minimize* O2 contact, not eliminate it completely as that would be very difficult and probably way over kill.

When I dry hop I just pull the orange cap off, pour in my hops, then blow CO2 into the neck for a few seconds then re-attach cap, inflate balloon and pop on. It's obviously easier with the cap that has the gas post on it.

I need to get a 5lb tank for inside my camber so I can just attach the gas at .5lbs all the time. Using just the balloons you have to re-fill them at least 2x a day during the cold crash.

Once I have that I can do 2x brews with just the orange caps and some hose. Like this: (I realized I couldn't get the gas in without drilling a hole in the fridge so I went with the balloons right after this picture)

 

[fun4stuff]

You can't completely avoid exposing it to the air. We're trying to *minimize* O2 contact, not eliminate it completely as that would be very difficult and probably way over kill.

When I dry hop I just pull the orange cap off, pour in my hops, then blow CO2 into the neck for a few seconds then re-attach cap, inflate balloon and pop on. It's obviously easier with the cap that has the gas post on it.

I need to get a 5lb tank for inside my camber so I can just attach the gas at .5lbs all the time. Using just the balloons you have to re-fill them at least 2x a day during the cold crash.

Once I have that I can do 2x brews with just the orange caps and some hose. Like this: (I realized I couldn't get the gas in without drilling a hole in the fridge so I went with the balloons right after this picture)

What about just putting a bung/cap on the carboy when cold crashing? Do you think air still gets in?

 

[beskone]

What about just putting a bung/cap on the carboy when cold crashing? Do you think air still gets in?

The problem is the negative pressure that would occur if you sealed up the top has the potential to shatter a glass carboy, or crack a plastic one.

You need some positive pressure to reduce / eliminate this.

Lots of people just use an S type airlock and accept the fact they are introducing air into the vessel. Some people use an extra long blow off tube so they don't suck liquid back (although when you remove the tube there will still be a bit of negative pressure and you'll still get air in the vessel)

 

[doug293cz]

I was going by the math in this post, https://www.homebrewersassociation.org/forum/index.php?topic=15079.msg191470#msg191470

I normally vent the head space after filling with beer 5x at 30psi. It has been working well for me, my hoppy beer rarely lasts over a month. Ones that I have bottled off the keg sitting for a month got 41s recently in World Cup of Beer. Is doing another 5 purges that big of a difference? Are you a c02 supplier ?

The math in that post is wrong. It gets corrected further down in the thread.

Oxidation will take longer at lower temperatures, and a month is probably not long enough for much to happen, with your O2 levels and your ability to perceive flavor degradation.

No, I am not a CO2 supplier.

If you are happy with how your beer holds up in storage, then there is no need to change your practices. The advice is offered for those who say the hops really pop in their freshly kegged IPA's, but after a week or two the hops become muted and muddled. It's a fairly common complaint around here.

Brew on

 

[JasonG]

Exactly. It's quite handy to have...

Cheers!

I've actualy thought before about attaching a CO2 balloon to my fermenter caps before, especially during cold crashing, but never actually put something like this together (and frankly thought myself a little crazy for considering it). I really like your set up!

How much pressure are you fermenting under? The blue balloons look less filled than the black ones, but I imaging the PSI is quite low in either case.

Do either of you have a DO meter? I would be very interested to see what this approach does to your DO level. It would be great to ferment two IPAs under the same conditions, but one with this minimal O2 set up, and the other with a more conventional set up, and then measure DO and do a triangle taste to see how much of a difference it makes.

Thanks for the inspiration!

JG

 

[doug293cz]

It mentions 4 months with "cold" storage. Probably why the taste difference isn't really noticable at homebrew scale.

That's 4 mos. of cold storage at 0.1 - 0.2 ppm TPO. Oxidation will occur faster at higher O2 levels.

Anyways, doesn't sound like one can really estimate TPO without a DO meter. So any number of purges is more of a guesstimate. Of course closed transfers would be optimal.... Assuming you have some way checking sg and dry hopping without opening fermentor.

Yes, to actually measure TPO you need a DO meter. But, the TPO contribution of headspace O2 can be calculated, and the TPO cannot be less than the headspace contribution to TPO. If the TPO contribution from the headspace is 100 ppm, you're in trouble no matter how low the DO in the beer. And purges won't affect the DO in the beer (initially). DO needs to be addressed separately. Freshly fermented beer has extremely low DO. The DO builds up with O2 exposure between fermentation and packaging. Sampling SG just requires a spigot on the fermenter. Dry hopping presents a more significant challenge.

That's a lot of co2 though....at least 30% of a 5 lb tank just to transfer? Might as well buy a dedicated 10+ lb tank just for transfers.

I think the 30% estimate is high. It takes ~6 gal of CO2 to push StarSan out of a keg. It takes 5 gal * 1.7 volumes = 8.5 gal to add 1.7 volumes to beer starting with 0.8 volumes after fermentation. It takes another 5 gal * (10 psi + 14.7 psi) / 14.7 psi = 8.4 gal to serve 5 gal of beer @ 10 psi. So each keg takes 6 + 8.5 + 8.4 = 22.9 gal of CO2 at 14.7 psi. The liquid purge take 6 gal / 22.9 gal = ~26% of total CO2 usage, assuming you don't consume CO2 in places other than what's outlined above. Any additional keg venting during storage/serving will reduce the percentage of total CO2 used to push StarSan.

I don't know if there's a point if you can't tell a difference in taste though, assuming beer will be drank within a couple months and kept cold. I'm just trying to separate homebrew myth from good practice: so many of these recommendations from the commercial industry don't lead to significant difference in taste at homebrew scale.

If you're not tasting degradation of your beers between kegging and kicking the keg, then there is no reason to change your ways. Many brewers claim to notice significant degradation, and I have no reason to doubt them. Advice on how to lower O2 exposure is aimed at them.

Brew on

 

[beskone]

I don't have the ability to attach gas directly to the caps when the chamber is closed so I fill the balloons as full as possible knowing I'm going to have to re-fill them 2x a day. He's got gas running at positive pressure all the time so it's just enough to slightly fill the balloons up as an indication of pressure.

As soon as I get a 5lb tank I'll set it up directly to the gas as well.

I've actualy thought before about attaching a CO2 balloon to my fermenter caps before, especially during cold crashing, but never actually put something like this together (and frankly thought myself a little crazy for considering it). I really like your set up!

How much pressure are you fermenting under? The blue balloons look less filled than the black ones, but I imaging the PSI is quite low in either case.

Do either of you have a DO meter? I would be very interested to see what this approach does to your DO level. It would be great to ferment two IPAs under the same conditions, but one with this minimal O2 set up, and the other with a more conventional set up, and then measure DO and do a triangle taste to see how much of a difference it makes.

Thanks for the inspiration!

JG

 

[day_trippr]

[...]How much pressure are you fermenting under? The blue balloons look less filled than the black ones, but I imaging the PSI is quite low in either case. [...]

The regulator is open just enough to lift the low pressure gauge needle off its stop.
I've never measured the actual pressure as I don't have another gauge any more accurate than what's on the regulator.

But it's low enough that the balloons don't actually inflate - they just stand at attention
(I'm guessing the apparent difference in the pic is just variation in the balloons themselves).
It takes a couple more PSI to get the balloons to grow.

I did a cold-crash experiment recently where I filled the balloons then shut off the CO2.
As related by another member, you end up having to refill the balloons a couple times a day (at least) as the temperature drops, first to account for contraction effects, and then because the CO2 is dissolving into the very cold beer (33-34°F).

Certainly doable, my setup just conveys convenience.

All the carbing gear in that fridge was there for the occasional over-flow of kegs from my actual cold-carbing fridge, and the rest of the bits I was already using for CO2-push transfers, so really my extra investment was a bag of balloons

Cheers!

[edit]ps: the original intent (and continued use) of the balloon was for a "gas fuse" to blow up instead of the carboy in case anything went terribly wrong...