Pressurized Closed Loop Corny Keg Fermenting

[chieftain]

So you’re tossing pellet hops in loose into an empty keg that hasn’t been purged and just relying on fermentation CO2 to purge the O2 from the keg? I’ve never tried this, so I don’t have any data to say this would be a problem, but intuitively, exposing hops to a keg full of ambient air at fermentation temps would seem like it might oxidize the hops before the fermentation can purge all the O2 from the keg. If you haven’t noticed any negative effects, maybe it’s not as much of a concern as I would have guessed. Good to know and maybe gives me a few more options to consider, thanks!

I've done this a few times, and I am a little leery of the oxidation factor, but the beers have turned out decent. Last one I did had 4 or 5 oz of Denali and it had a distinct pineapple nose for the duration of the keg (3 weeks or so).

 

[BeerFst]

I think there was a post in this thread but maybe I saw it somewhere else. It was all about the math of gas dilution but the summary is that you can’t really push out o2 using the heavier c02. Rather you just create a gas mixture that becomes more and more o2 dilute as you increase the amount of c02. So the total amount of o2 remains the same in the keg. The only way to remove it would be to burp the keg then replace against with co2. Rinse and repeat. Now we already know that just purging and venting isn’t an effective way to do a keg however I’d you reduce the volume of air possible, aka by transferring the beer to the water purged keg before dry hop, then opening to add dry hop and lastly venting and purging the smaller volume, you might actually reduce o2 exposure to the bulk of the Beer.

On a completely random note, for those that use fermcap, has yours ever “frozen” in the bottle? This was my first time using it and mine was completely frozen. I was able to warm it up enough to get some gel into the keg last week. I had stuck it in the back of the fridge when I got it from NB per the instructions on the bottle, so I had assumed I got it too close to the condenser and it got way to cold. Howver now it’s in the front of the fridge and it’s still solid.

 

[Hannabrew]

I've done this a few times, and I am a little leery of the oxidation factor, but the beers have turned out decent. Last one I did had 4 or 5 oz of Denali and it had a distinct pineapple nose for the duration of the keg (3 weeks or so).

Nomally I don't water purge anymore but when I want to DDH in the keg my method is to water purge the keg, make sure it is done dry, add the hops, and then immediately hook up fermentation gas to purge what I introduced while adding the hops.

 

[Veets]

So you’re tossing pellet hops in loose into an empty keg that hasn’t been purged and just relying on fermentation CO2 to purge the O2 from the keg? I’ve never tried this, so I don’t have any data to say this would be a problem, but intuitively, exposing hops to a keg full of ambient air at fermentation temps would seem like it might oxidize the hops before the fermentation can purge all the O2 from the keg. If you haven’t noticed any negative effects, maybe it’s not as much of a concern as I would have guessed. Good to know and maybe gives me a few more options to consider, thanks!

This is my first time trying it, based on reading about it from others. If it goes badly I'll report back!

 

[TimmyWit]

for those that use fermcap, has yours ever “frozen” in the bottle?

Never, and I have been using it for years

 

[cheesebach]

Nomally I don't water purge anymore but when I want to DDH in the keg my method is to water purge the keg, make sure it is done dry, add the hops, and then immediately hook up fermentation gas to purge what I introduced while adding the hops.

How do you make sure the keg is totally dry after water purging? Or do you just mean draining as much of the liquid out as possible through either the liquid or gas post?

 

[cheesebach]

I think there was a post in this thread but maybe I saw it somewhere else. It was all about the math of gas dilution but the summary is that you can’t really push out o2 using the heavier c02. Rather you just create a gas mixture that becomes more and more o2 dilute as you increase the amount of c02. So the total amount of o2 remains the same in the keg. The only way to remove it would be to burp the keg then replace against with co2. Rinse and repeat. Now we already know that just purging and venting isn’t an effective way to do a keg however I’d you reduce the volume of air possible, aka by transferring the beer to the water purged keg before dry hop, then opening to add dry hop and lastly venting and purging the smaller volume, you might actually reduce o2 exposure to the bulk of the Beer.

I'm not sure I'm following what you're trying to get at here - what you're saying about the total O2 remaining the same in the keg only applies if the gas inside the keg isn't allowed to escape. The fermentation purge methods suggested in this thread rely on allowing gas to escape through the gas in post as fresh fermentation CO2 is pushed in through the liquid out post. Basically, a continuous "burping". So the total amount of O2 remaining in the keg steadily decreases throughout the fermentation, reaching negligible levels by the time fermentation completes.

Theoretically, the lowest overall O2 exposure method for adding dry hops to the secondary/serving keg is what Hannabrew suggested above - water purge the keg, open to add dry hops quickly while flushing with CO2, then hook up to an active fermentation to flush out any O2 that got in while adding the dry hops. However, this method requires leaving hops in an empty keg at near-room temps in a moist environment for a number of days. It may be relatively safe since the keg should be pretty well flushed of O2, but you may be letting some of the aroma escape this way as well as possibly introducing other risks by having warm hops sitting out inside a damp keg for a period of time. My guess is that those risks are probably minimal, but I'm also not sure how much better it is O2-wise than waiting until dry hop time to open the keg to add the dry hops while flushing with CO2.

 

[BeerFst]

I agree with what you mentioned above, but the way the first post read was that the user was NOT doing the water purge to get all c02 in there. so i was just suggesting that there would be substantial O2 for a while as the keg purges from being filled with plain air.

I was also making the argument that the max amount of O2 is limited by the available volume of air. Basically if you open the water purged, and empty SV to add the dry hops you could displace the C02 100% and end up with ~20% O2 (found in normal air). I realize that is the absolute worst case and not likely. But in this example you are relying on the fermentation gases to displace "1 gallon" of O2. Then at that point as you transfer to SV you are exposing the beer to O2 the whole time during transfer.

Instead if you transferred the beer to water purged keg, then opened the lid, your max o2 content would only be 20% of the headspace, which could be very small, but lets say its 1 gallon. so you have cut the actual o2 present by one fifth. In this case you would have to rely tank gas to purge that keg, but i would argue it easier to remove/reduce the .2gallons o2 than the one gallon in the other example.

I think either way you will end up about the same, though in the latter the dry hops would be "fresher."

at what rates do hop creep start? a 3oz dry hop is ~1lb/bbl, will the hop creep eat up that remaining o2 anyway?

I'm also curious about how what we are doing compares to what pros do? like even if they have a hop back, torpedo or similar to fill with beer then push back into the main FV, they would still just be flushing that vessel with C02, similar to how we would flush a keg without the water purge. So what are they doing that is all that different? I saw a video from founders when they were dry hopping All Day and it looked like they had just opened up the FV then dumped 100s of pounds of hops in

 

[Hannabrew]

How do you make sure the keg is totally dry after water purging? Or do you just mean draining as much of the liquid out as possible through either the liquid or gas post?

yeah I let the keg sit for a few hours after initially draining it to let all the water settle and then drain it one last time. It doesn't get every last drop out I'm sure but I can live with that. BTW when I do this method of keg hopping I suspend the hops in a SS hop filter so there's no issue with moisture and also so that they're not in the beer the entire time the keg is tapped.

 

[cheesebach]

I agree with what you mentioned above, but the way the first post read was that the user was NOT doing the water purge to get all c02 in there. so i was just suggesting that there would be substantial O2 for a while as the keg purges from being filled with plain air.

I think we're both in agreement here - adding hops to an un-purged keg at room temps is likely asking for trouble. It may work fine, but I doubt anyone will argue that it is the "best" way.

I was also making the argument that the max amount of O2 is limited by the available volume of air. Basically if you open the water purged, and empty SV to add the dry hops you could displace the C02 100% and end up with ~20% O2 (found in normal air). I realize that is the absolute worst case and not likely. But in this example you are relying on the fermentation gases to displace "1 gallon" of O2. Then at that point as you transfer to SV you are exposing the beer to O2 the whole time during transfer.

This is definitely being overly pessimistic. With 3-5 psi of CO2 pressure coming in from the bottom, there's not going to be much O2 ingress during the 15s it takes to pop the lid, dump in hops, and put the lid back. You can always purge the headspace after you fill the keg, and foaming will be minimized since you won't need to release the pressure on the beer at any point in time.

Instead if you transferred the beer to water purged keg, then opened the lid, your max o2 content would only be 20% of the headspace, which could be very small, but lets say its 1 gallon. so you have cut the actual o2 present by one fifth. In this case you would have to rely tank gas to purge that keg, but i would argue it easier to remove/reduce the .2gallons o2 than the one gallon in the other example.

This post-fermentation/carbonation dry hopping became a hot topic this week after I shared my experience of being unable to open the keg to add hops after the beer was carbonated without creating a foam volcano. If you are even able to open the lid to add dry hops when the beer has been transferred to the serving keg, adding the dry hops will for sure start a foam surge that you'd only have a couple seconds to react to. Assuming you manage to get the lid back on, any O2 introduced would have a much larger surface area to get to work on from all the foam that was just created, and you may have a hard time purging the headspace as well if it's filled with foam.

I don't mean to come across as being argumentative here, but based on my recent experience, I won't be releasing the pressure on carbonated beer (either in primary or the serving keg) for the purposes of adding dry hops again. If you have ideas for managing the foaming aspect of this, please do share, as I was originally hoping I could do all my dry hopping in the primary.

 

[TimmyWit]

I don't mean to come across as being argumentative here, but based on my recent experience, I won't be releasing the pressure on carbonated beer (either in primary or the serving keg) for the purposes of adding dry hops again. If you have ideas for managing the foaming aspect of this, please do share, as I was originally hoping I could do all my dry hopping in the primary.

I haven't had any issues so long as the pressure is reasonable. I also use Fermcap S in the boil and that may help. I keep it around 10-15 psi until I get the dry hops in. If you get much past 20 psi, I don't think there's any way around the volcano. If you want to add it after fermentation is complete, you might have to crash it first to drop the pressure.

 

[cheesebach]

I think the first time I tried it on this batch pressure was around 20psi and temp was 65F. I tried again a day later at 16psi and 60F - same story. I don’t use fermcap anywhere, so that might account for some of the difference. Also, I used WLP066 this time which is a top cropper like WY1318. Both seem to leave a thick krausen that seems like it can’t wait to rise up again at the first chance it gets.

 

[BeerFst]

Assuming you manage to get the lid back on, any O2 introduced would have a much larger surface area to get to work on from all the foam that was just created, and you may have a hard time purging the headspace as well if it's filled with foam.

But the you can cap on foam!! Jk. I know you just wrote that post but I still forgot about it. You have convinced me there’s no way to do it and use the spund to carb with the original extract.

Honestly I’m not a huge ddh guy when it comes to neipa. I’m def one to define ddh as dryhopping twice as opposed to dry hopping double the normal amount but in homebrew land maybe this is the simple way to go. And if you want it to be keg hopped then just do the bio transform hop in the sk and leave them in. Again not that I have one, but sounds like it would work pretty easily with the cbds.

The only other half solution I think would be to rely on priming sugar and just give the whole process and extra week. Next two Hoppy beers planned will be NE, but after that I want to do the MACC ipa from brulosophy. I really don’t want to do a high Krausen hop for that so I’ll probably just consider force carbing like I have for years or maybe try the priming sugar.

 

[TimmyWit]

I think the first time I tried it on this batch pressure was around 20psi and temp was 65F. I tried again a day later at 16psi and 60F - same story. I don’t use fermcap anywhere, so that might account for some of the difference. Also, I used WLP066 this time which is a top cropper like WY1318. Both seem to leave a thick krausen that seems like it can’t wait to rise up again at the first chance it gets.

Why not keep the pressure at or even under 10 psi until you get the dry hop in? I do think the fermcap will help as well.

The higher the pressure, the more difficult it is to open that top without having problems. Try setting your spund valve to 5 psi. You can tighten it after you add the dry hops and you will have plenty left to naturally carbonate assuming you catch it with 5 points or so remaining. It might even be less than that but I don't think it takes much.

I honestly haven't had any issues dry-hopping in a fermenting keg aside from the one time I tried to open it at 20ish psi. I can relate to exactly what you're talking about with that volcano but I don't see any need to have it that high until the last few points when you want to tighten it for natural carbonation.

 

[cheesebach]

Why not keep the pressure at or even under 10 psi until you get the dry hop in? I do think the fermcap will help as well.

My goal was to find a way to dry hop post-fermentation without having to resort to adding priming sugar (which would then wake the yeast up, possibly resulting in bio-transformation, defeating the purpose of waiting for active fermentation to finish). I know that what the differences are of an active fermentation vs. post-fermentation dry hop is debatable, but it’s something I’d like to test myself before going to active-fermentation only dry hopping for all my beers.

I think you’re right that fermcap (or another foam-inhibitor meant for fermentation) is probably the right way to go if I decide to attempt this again in the primary. For adding the hops to the secondary/serving keg, the method of adding hops to the empty/purged secondary and then transferring in under pressure worked great this time around.

 

[crane]

Also, I have one CBDS but also made a few of these:

http://think.gusius.com/diy-keg-floating-dip-tube

The DIY-type has a large filter at the inlet -

I just ordered enough supplies to make 3 of these. At under $10 a piece with a filter you can't go wrong compared to the $50+ you have to pay to get a CBDS with the filter. Thanks for sharing the link.

If these work out for me I can add this to all of my kegs for under $200 compared to over $1k for 20 CBDS with filters.

 

[BeerFst]

My goal was to find a way to dry hop post-fermentation without having to resort to adding priming sugar (which would then wake the yeast up, possibly resulting in bio-transformation, defeating the purpose of waiting for active fermentation to finish).

So why not abandon the spund on primary, dry hop in primary after active ferm. Then rack to sv and add priming sugar there? It’s pretty much the same as if you were bottling right? I mean I guess this isn’t really low o2. But you’d leave the dry hop behind in the primary limiting what biotranformation might happen. At least that’s my guess.

Also have we discussed hop creep on this thread? Hops have some diastatic power to break down some sugars to germentable and kick off again. I found a pretty neat presentation from alagash on the topic. they had bottles their first batch of hoppy table beer but didn’t leave enough time on the dry hops. Ferm kicked off again but after it was bottled and ended up with 4+ volumes in all the bottles.

 

[gnor]

I just ordered enough supplies to make 3 of these. At under $10 a piece with a filter you can't go wrong compared to the $50+ you have to pay to get a CBDS with the filter. Thanks for sharing the link.

If these work out for me I can add this to all of my kegs for under $200 compared to over $1k for 20 CBDS with filters.

Where did you order the stainless floating "ball"?

 

[stickyfinger]

So why not abandon the spund on primary, dry hop in primary after active ferm. Then rack to sv and add priming sugar there? It’s pretty much the same as if you were bottling right? I mean I guess this isn’t really low o2. But you’d leave the dry hop behind in the primary limiting what biotranformation might happen. At least that’s my guess.

Also have we discussed hop creep on this thread? Hops have some diastatic power to break down some sugars to germentable and kick off again. I found a pretty neat presentation from alagash on the topic. they had bottles their first batch of hoppy table beer but didn’t leave enough time on the dry hops. Ferm kicked off again but after it was bottled and ended up with 4+ volumes in all the bottles.

hop creep lives. i had a few ipas in cornys that pressurized for days. only explanation is hop creep

 

[crane]

Where did you order the stainless floating "ball"?

https://www.aliexpress.com/item/MK-...&terminal_id=e2c02df0ae5b45c3b18fa1cd15658151

 

[Andre3000]

I've been dry hopping at yeast pitch to avoid having to open the fermenting keg. There is some talk of off gassing the hop aroma during fermentation but it seems to work well enough for me to convince myself it's worth doing.

What pressure are you guys fermenting at? Lately I've been doing primary at around 10 psi then around day 4 I ramp it up before transferring usually hitting 20 no problem. Wondering if 10 is maybe a bit too high for primary.

I've also done away with the whole water filling co2 thing. It's just too time consuming for me, though it is effective, no doubt. I basically sanitize with starsan, purge it with co2 through gas post and purge it out the beverage post with a picnic tap and let the co2 run for a minute or so with the intent of getting a good portion of the o2 out. I rely on fermentation to push the remaining out during spunding. I have no idea how much o2 I'm exposing my beer to with this method.

 

[Veets]

I just ordered enough supplies to make 3 of these. At under $10 a piece with a filter you can't go wrong compared to the $50+ you have to pay to get a CBDS with the filter. Thanks for sharing the link.

If these work out for me I can add this to all of my kegs for under $200 compared to over $1k for 20 CBDS with filters.

Damn, that's a lot of kegs.
What does your pipeline look like? I mean what styles, and how long do they sit before tapping?

 

[crane]

Damn, that's a lot of kegs.
What does your pipeline look like? I mean what styles, and how long do they sit before tapping?

I keep 5 beers on tap all the time. I usually have 1 or 2 hoppy beers that I brew in 5 gallon batches, grain to glass in 2 weeks and consumed within a 4-6 weeks after tapping. I will brew non hoppy beers in 10 gallon batches and save the second keg such that I don't serve both kegs back to back. This means that some kegs sit for a few months in cold storage before being tapped.

I understand that if I'm letting kegs lager for a few months that I don't need these modifications to the keg to get clear beer from the get go, but I want all my kegs to be the same. I will use every last keg up before I clean any of them. This way I can clean and sanitize as many kegs at once on keg cleaning day. This method only works if all my kegs are the same.

 

[Hannabrew]

I like the clean em at once concept but doesn't that mean you have gaps in your beer availability? I would think I'd go nuts when there is one keg left and I have 4 empty taps. Plus I would think that makes you brewing schedule a feast or famine approach.

 

[BeerFst]

Voss blonde is in the SV. It was so freaking easy compared to the old ways of autosiphon, not to mention a breeze to clean up. Thank you thread! I hadn’t seen it mentioned or at least I don’t recall, and I certainly don’t think it novel but I transferred with the spund on the SK to reduce foam if there even was any. I was transferring at 33 but figured that’s how I fill bottles off kegs why not do my transfer the same way.

Yeast has definitely dropped far more but the beer is still quite hazy, pretty much the same as my recent neipa but no oats or wheat this time. I’m thinking my crush might have something to do with it though. It was my first time using my mill so I set it at .028 verified by a set of gauges. The result was near flour and in turn I had crazy efficiency(85%) beating my last moreBeer crush batch by 26%. I was pretty stoked. I also didnt use finings so that hasn’t helped clarity.

Taste is still yeast dominant but there are hints of orange occasionally. Basically no hop aroma though, I was surprised with that, I wonder if the high ferm temp messed with it at all. Similarly I’m thinking I did put the spund on too early and reduced ester output. So basically I have a pretty neutral tasting beer...haven’t given up all hope yet and will def be using this yeast again but I’ll leave the spund off to the very end.

On a slightly different topic I reached out to r/thebrewery for some pro insights on post ferm dry hopping. One response was do just as we are doing by dumping into purged keg and another to flow co2 thru the dip tube to keep flow going out. The only new pro specific mention was to use a torpedo or similar but they just simply flushed with co2, which must leave some o2 behind since it would be similar to not water purging. It didn’t sound like anyone was spunding either, though I didn’t ask specifically about hopping something post carb.

 

[Veets]

Voss blonde is in the SV. It was so freaking easy compared to the old ways of autosiphon, not to mention a breeze to clean up. Thank you thread! I hadn’t seen it mentioned or at least I don’t recall, and I certainly don’t think it novel but I transferred with the spund on the SK to reduce foam if there even was any. I was transferring at 33 but figured that’s how I fill bottles off kegs why not do my transfer the same way.

Yeast has definitely dropped far more but the beer is still quite hazy, pretty much the same as my recent neipa but no oats or wheat this time. I’m thinking my crush might have something to do with it though. It was my first time using my mill so I set it at .028 verified by a set of gauges. The result was near flour and in turn I had crazy efficiency(85%) beating my last moreBeer crush batch by 26%. I was pretty stoked. I also didnt use finings so that hasn’t helped clarity.

Taste is still yeast dominant but there are hints of orange occasionally. Basically no hop aroma though, I was surprised with that, I wonder if the high ferm temp messed with it at all. Similarly I’m thinking I did put the spund on too early and reduced ester output. So basically I have a pretty neutral tasting beer...haven’t given up all hope yet and will def be using this yeast again but I’ll leave the spund off to the very end.

On a slightly different topic I reached out to r/thebrewery for some pro insights on post ferm dry hopping. One response was do just as we are doing by dumping into purged keg and another to flow co2 thru the dip tube to keep flow going out. The only new pro specific mention was to use a torpedo or similar but they just simply flushed with co2, which must leave some o2 behind since it would be similar to not water purging. It didn’t sound like anyone was spunding either, though I didn’t ask specifically about hopping something post carb.

How can you tell if foam was reduced? I thought that a benefit of "closed loop" transfer was that foam was reduced because you're basically pouring beer from one vessel to another at the same pressure - equalized because the gas ports are connected. It sounds like you might have had the same effect if you left the spunding value on, but you vented some aromatics maybe.

By the way, be very careful in hooking up your lines for a closed loop transfer. It's been said before but maybe can't be emphasized enough. I accidentally crossed them (gas-out to liquid in, like during fermentation) last time, and when I removed the connector from the liquid line on the fermenter keg to fix it, there must have been a small hop particle or something in the QD. It was open just enough to spray beer on the ceiling and adjacent walls.
(Although it gives me another argument for a dedicated brew room)

 

[BeerFst]

How can you tell if foam was reduced? I thought that a benefit of "closed loop" transfer was that foam was reduced because you're basically pouring beer from one vessel to another at the same pressure - equalized because the gas ports are connected. It sounds like you might have had the same effect if you left the spunding value on, but you vented some aromatics maybe.

By the way, be very careful in hooking up your lines for a closed loop transfer. It's been said before but maybe can't be emphasized enough. I accidentally crossed them (gas-out to liquid in, like during fermentation) last time, and when I removed the connector from the liquid line on the fermenter keg to fix it, there must have been a small hop particle or something in the QD. It was open just enough to spray beer on the ceiling and adjacent walls.
(Although it gives me another argument for a dedicated brew room)

Haha I’ve been there...when we moved apartments my now wife found some that had sprayed on the wall that I missed and she was very very not happy. My keezer and stuff is in our unfinished basement now so that gives me at least a Few minutes to clean it up before she finds it haha. Though then again one tap was leaking a bit ago...she found it.

As for the foam, I can’t actually tell. And if you followed OPs method to the T I think you are correct. But I don’t have spare gas QDs to link them like that, only a liquid jumper to push it over or gravity it over (I pushed this time). So for me it was either open the poppet and vent pressure build up that way(actually more similar to how I would fill bottles and I can confirm those fill way easier and with less foam with back pressure), or do what I did. I didn’t daisy chain the kegs this time during ferm, just did water purge on my SK and had my FV cold crashing with gas on it at around 8psi. In a previous post I mentioned that I had set it for 30psi with Beer temp of 90 so that only netted me 2 volumes. The 8psi was the right number for 2.5 at 33F. So is OPs method better, I think yes, but I didn’t end up following it all the way. I was more looking for the o2 prevention than anything else. Honestly I’ve never really bought into the keep aroma in the keg, if you open the poppet you are losing it theory. I certainly lost no more aroma doing this tonight than I would have with the spund on during peak ferm, so I doubt this is the cause of my lack of aroma now. Like to an extreme i would agree that leaving it at atmospheric pressure for an excessively long time would lose considerable aroma though I’m not convinced this wouldn’t be partially from oxidation. I don’t think the small amount that might volatize by venting during a transfer or a handful of poppet pulls would be detectable (paging brulosopher, brulosopher to the thread please).

Also I definitely didn’t fill my basement with beautiful orange smells during the transfer. Funny thing is, though I haven’t tasted that much orange on the way down...my burps are wonderfully complex with spicy orange.

 

[crane]

I like the clean em at once concept but doesn't that mean you have gaps in your beer availability? I would think I'd go nuts when there is one keg left and I have 4 empty taps. Plus I would think that makes you brewing schedule a feast or famine approach.

You took that too literally. I do keep all 5 taps flowing all the time. I don't wait until every keg I own is dirty to clean them, but I usually try to avoid cleaning less than 8 kegs at a time.

 

[schematix]

Here’s pics of actual fermentation purge.

 

[duelerx]

Here’s pics of actual fermentation purge.

View attachment 577369View attachment 577370

What PSI do you use on your spunding valve?, thanks for the pics.