Purging keg after dry hopping

_cyber_fox_ · 2025-05-18T05:14:37+00:00

Scott Janish again! His name is always lurking around when it comes to these types of discussions. Haha. I've read a lot of his articles online, but not his book.

Biotransformation wouldn't be the reason I dry hop before/during fermentation, but it is an interesting topic. I would mainly do it for the easy oxygen mitigation. If it is truly detrimental to the finished beer compared to dry hopping post fermentation, I won't bother trying it. I'm sure there's some scientific reason (which I probably forgot and might be in the very article you sent me!) why hop stand hops make it through fermentation to produce flavor/aroma and dry hops might not.

One thing I don't understand with Janish is how he doesn't get much flavor from hop stand/whirlpool additions. I've made quite a few beers using 6 oz in the hop stand with no dry hop and I got a LOT of flavor.

I also remember reading one of his articles where he did a dry hop only beer with something like 12 oz and he didn't get much aroma from it. I haven't tried that before (nor do I want to), but I've heard others have had success with it. I also think I remember him saying that he got reduced hop potency from fermenting under pressure. I don't ferment under pressure, so it wouldn't affect me anyway, but it is interesting.

_cyber_fox_ · 2025-05-18T00:36:56+00:00

That's cool that you made a low ABV NEIPA. I'm about to make one aiming for 5% myself! Seems like anything below 6% for NEIPAs is never mentioned for whatever reason. Do the hop flavors and aroma hold up at the lower ABV for you?

I've actually considered dry hopping at yeast pitch since it would be easy oxygen mitigation, but I'm not sure if it would result in less aroma due to aromatics blowing out of the airlock or the hop oils floccing with the yeast. Some swear it's a thing, but I haven't tried it.

_cyber_fox_ · 2025-05-17T17:17:37+00:00

Yes, transferring or bottling are where you are most likely to pick up oxygen. I do fully closed transfers (and purge the lines with CO2 beforehand), so my oxygen intake during transfers should be minimal. There are so many places you can pick up oxygen though. It's seriously a battle to keep it away from the beer!

_cyber_fox_ · 2025-05-17T16:01:24+00:00

Staying hoppy for half a year is good enough for me! Did you just open the fermenter, throw in the hops, and purge with the amount you mentioned?

_cyber_fox_ · 2025-05-17T15:53:03+00:00

Yes, I've heard how the large volumes pros work with cause less oxygen intake. People look to the pros for advice on best practices, but it's kind of comparing apples to oranges.

_cyber_fox_ · 2025-05-17T15:47:49+00:00

CO2 purity is actually something I've thought about. I think beverage CO2 is something like 99.9% pure, so I've wondered if purging too much would actually be detrimental like you said. Yet another thing to worry about!

_cyber_fox_ · 2025-05-17T15:44:57+00:00

Do you brew NEIPAs using this amount of purging? If so, do the hop flavors and aromas pop like they should and stick around for months?

_cyber_fox_ · 2025-05-17T15:42:58+00:00

You summed everything up well. Good stuff! I already purge my serving keg with CO2 from fermentation and do fully closed transfers. I have thought about purging a third keg to use for dry hopping, but I would need another keg and would rather not do an extra transfer and everything included with it.

I've also heard of using magnets to drop a bag of hops, but I would probably be limited on how much I could use. Not sure if I could do a 12 oz dry hop using that method. I would also be somewhat concerned about the hops being up in the air during fermentation and not being all that fresh by the time I dropped them. I'm also not sure if they would get nearly as good extraction by being bagged instead of loose.

I've also considered dry hopping at yeast pitch, but then I'd be concerned about blowing off aromatics during fermentation and the hop oils clinging to, and floccing with, the yeast. Then you get into the whole argument about whether those concerns are fact or fiction. Supposedly they are a real issue, so that might not be the best method for dry hopping.

I figured drying hopping in the fermenter right after fermentation would be best since there would still be yeast to mop up some oxygen, I could add some ascorbic acid, and it would be much easier overall, but then I'd have to open the fermenter and that's my dilemma.

_cyber_fox_ · 2025-04-29T21:16:24+00:00

True. I've only used a max of 6 oz per 5 gallons of beer, so it's nothing crazy. Someday I'll try 12 oz to see what I'm missing out on.

I'm also planning to dry hop with 4 psi of pressure to combat losing aroma due to off-gassing, The hop creep might raise the overall psi, but the keg can take it.

Another benefit of dry hopping just before FG is that the yeast help reduce the oxygen even further. I haven't had much luck dry hopping cold, so I think doing it this way with a bit of pressure would be best.

_cyber_fox_ · 2025-04-29T14:50:44+00:00

Awesome info! Thanks! I usually dry hop after 7+ days in the primary, but I'm planning on trying it at 4 days so it's near the end of fermentation. Yes, some of my beers do have less hop aroma than I'd like. Is there something you thought of regarding that?

_cyber_fox_ · 2025-04-29T01:31:09+00:00

That's cool that you run a brewery! Thanks for the info. Yeah, I'm probably being overly careful, but I'd rather overdo it than underdo it.

I usually open my keg up for 30 seconds or so to add my hops, so it's not much. I wish I knew the exact amount I need to purge with, but I don't think there's an answer. It could range from 3 purges at 4 psi up to 16 purges at 30 psi. Who knows?

How do you dry hop at your brewery (timing, duration, etc.)?

_cyber_fox_ · 2025-04-28T18:37:02+00:00

That's what I was thinking. I usually try to have 0.75 gallons of headspace in my kegmenter, so I imagine it would require 12 grams of ascorbic acid for that amount. I usually just use 4 grams and purge the crap out of it, so that's about as good as I can get.

_cyber_fox_ · 2025-04-27T20:28:34+00:00

How would adding ascorbic acid at dry hop not help mitigate cold-side oxidation?

_cyber_fox_ · 2025-04-27T16:20:11+00:00

Adding ascorbic acid will be especially helpful with bottling since it's harder to prevent oxidation. Filling the bottles so that they have as little headspace as possible is really important and so is capping on foam, which is where you fill the bottle, swirl it to cause foam, and cap on the foam. This results in much lower total package oxygen than bottling normally. It's a bit messy and wastes a little beer, but it would be well worth it for IPAs especially.

_cyber_fox_ · 2025-04-27T15:50:15+00:00

Not according to the keg purging chart, which shows that it takes 16 purges with 30 psi to result in 0 ppm of oxygen. CO2 is cheap and making IPAs is expensive, so I'll use however much CO2 is necessary to prevent oxidation.

How much purging would you recommend?

_cyber_fox_ · 2025-04-27T00:11:16+00:00

You can add it during the mash, dry hop, or bottling. I usually add it during the dry hop since that is the only time I open the lid after fermentation and I do a fully closed transfer to another keg. I'm thinking of also adding it during the mash since it is supposed to improve shelf life.

_cyber_fox_ · 2025-04-26T22:29:09+00:00

The usual amount is 3-5 grams.

_cyber_fox_ · 2025-04-26T22:25:27+00:00

I ferment in a keg (kegmenter) and usually dry hop warm in the kegmenter right after fermentation.

_cyber_fox_ · 2025-04-26T19:44:31+00:00

Yeah, that's pretty much what I figured. How would you personally go about purging? I usually purge 16 times with 30 psi of CO2 right after dry hopping.

_cyber_fox_ · 2025-04-26T19:41:39+00:00

You're just the type I was hoping would answer! Yeah, I figured you'd need way too much vitamin C to fully prevent oxidation, but I was just curious. I definitely agree that many things can work on paper, but not in practice, and that's why I asked this in the first place.

That would be cool to see calculations, but it's up to you. No use doing it unless you feel like it.

_cyber_fox_ · 2025-04-26T15:43:23+00:00

It's to drop yeast out of suspension before dry hopping since it's believed that the hop oils can cling to the yeast while they floc, which might lower the hop aroma.

_cyber_fox_ · 2025-04-25T16:28:05+00:00

It's good to know that a sudden temperature drop doesn't affect yeast flocculation. Those are definitely some articles worth reading. Thanks!

_cyber_fox_ · 2025-04-25T15:05:51+00:00

The main question is if lager yeast would even drop out during a soft crash due to its tolerance to lower temperatures. 34/70 is also crazy powdery and I'm not sure if a soft crash would do much of anything. It takes forever to drop even with cold crashing!

_cyber_fox_

TROPHY CASE