Reducing oxygen from dry hopping- add hops early or suspend above beer?

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josephort

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As I've continued to experiment with NEIPAs, it's become clear to me that minimizing oxidation is key to brewing excellent examples of the style. I'm not yet at the point where I'm worried about hot side aeration, but I'm trying to do everything I can do get cold side oxygen exposure as close to zero as possible. I've switched to fully closed transfers for packaging, but now I want to address the risk of oxygen from dry hopping.

The typical advice for minimizing O2 during dry hopping is to dry hop while fermentation is still active, so that O2 in the headspace is pushed out the airlock and O2 introduced into the beer as scavenged by the yeast. The downside of this is that you lose hop flavor and aroma as CO2 bubbles away, and you have to do fairly long dry hop which many people seem to think is not ideal.

An alternative raised in this thread is to hang your dry hops in the head space of your fermenter, let them sit there during active fermentation, and then drop them into the beer at the appropriate time. I have successfully done a trial run of this in my big mouth bubbler by having a hop bag suspended on a piece of thread running through an S airlock. This is sort of a PITA to set up but I can confirm it works fine; the bag will happily hang out indefinitely at the top of the fermenter, and I can drop it into the beer whenever I want without opening the lid.

I am considering doing this for my next NEIPA. The question I have is, is it actually better than just dry hopping during active fermentation? The hops will be in contact with the beer for less time, and won't be in contact at all while it's bubbling, but they will be hanging right under the airlock for a week or more with CO2 slowly pushing around and through them into the atmosphere. Is this going to strip off flavor and aroma just as much as early dry hopping would? Or are the hops less susceptible to the loss of aromatic compounds while they're dry and still in pellet form?

I'm not sure if anyone's actually done the experiment to demonstrate conclusively whether or not this works, but I know everyone has a lot of opinions about oxygen, hops, and NEIPA brewing, and I'd love to hear them applied to this particular idea!
 
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I can't answer for sure but I would "THINK" that the passing of CO2 through the hops for this time would drive off the aromas. Like I said I would just be speculating but that would be my thought. Obviously to combat this you would likely just need to add more hops in your suspended bag.

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McMullan

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As long as the hop pellets remain dry and intact I can't see much aroma being stripped from them. Do they have to be in place at the beginning or can they be placed some time later, before CO2 production stops? I haven't tried it myself yet, but I wonder if adding a little ascorbic acid/vitamin C just before dry hopping helps to reduce the oxidant level from the hops. An interesting experiment for someone more familiar with NEIPAs. Another strategy is to use a secondary vessel containing the hops and purged using CO2 from fermentation in the primary. With good transfer technique, and maybe a little vitamin C added, I think that is going to work well.
 

RyPA

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In my most recent NEIPA, I fermented and served from the same keg. When pitching yeast, I stuck the dry hop back to the inner wall of the keg using magnets, and slid them down into the beer on day 5. The keg was closed from yeast pitch until the keg was kicked. The beer turned out awesome and looked like OJ until the final glass. No off flavors from sitting on the yeast.

Here's the thread Upcoming single-hop NEIPA brew day
 
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josephort

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Appreciate the input so far!

I would "THINK" that the passing of CO2 through the hops for this time would drive off the aromas.
As long as the hop pellets remain dry and intact I can't see much aroma being stripped from them.
Both of these arguments make intuitive sense to me, which is why I feel uncertain! Hoping to hear more from people with either a lot of experience with different dry hopping strategies or else very detailed knowledge of hop biochemistry. Or maybe someday the Brulosophy guys will do this experiment and give us definitive answer...

In my most recent NEIPA, I fermented and served from the same keg. When pitching yeast, I stuck the dry hop back to the inner wall of the keg using magnets, and slid them down into the beer on day 5. The keg was closed from yeast pitch until the keg was kicked. The beer turned out awesome and looked like OJ until the final glass. No off flavors from sitting on the yeast.

Here's the thread Upcoming single-hop NEIPA brew day
This is useful info, and suggests to me that my strategy will be able to produce a good beer. Still, the scientist in me can't help but nag that there's no control group, so we can't really say whether your magnet strategy or my string strategy would work any better than just doing the dry hop charge during active fermentation.

Do they have to be in place at the beginning or can they be placed some time later, before CO2 production stops?
I had been considering this, and I think I will try to hang the bag as fermentation is winding down. Hopefully this will allow enough CO2 to pass through the hops to purge them of any O2, but not enough to significantly strip volatile compounds. Maybe I will do one early dry hop charge at the same time that I suspend the bag- that way I can at least call it DDH!
 

RyPA

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@josephort Yes, string or magnets, its the same concept. But IMO, with magnets you are 100% sealed where as with a string, though probably negligible, there has to be a small gap for the string to come through your airlock?
 
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josephort

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there has to be a small gap for the string to come through your airlock?
Just to be clear, the way I'm doing this has the string running through the regular chambers of the S airlock, passing through the sanitizer. There's no additional hole.
 

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I've been hanging cheap loose woven muslin (I think) bags with magnets. Certainly works well as a process.

Hop flavors are crazy, so if any are lost it's hard to imagine. I think most of it's buried inside the pellets anyhow, they aren't hanging there as exposed powder. On the chance that's the case I suppose I'd just add more next time to compensate but sort of doubt it.

Even a brief fermenter open time will introduce oxygen, but I'd expect that with a purge or two of CO2, especially if it's combined with active fermentation would tend to mitigate anything detrimental being noticed.

I expect there are several, fairly equivalent ways to go about it. The best one is really whatever works for you.
 

BongoYodeler

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As I've continued to experiment with NEIPAs, it's become clear to me that minimizing oxidation is key to brewing excellent examples of the style. I'm not yet at the point where I'm worried about hot side aeration, but I'm trying to do everything I can do get cold side oxygen exposure as close to zero as possible. I've switched to fully closed transfers for packaging, but now I want to address the risk of oxygen from dry hopping.

The typical advice for minimizing O2 during dry hopping is to dry hop while fermentation is still active, so that O2 in the headspace is pushed out the airlock and O2 introduced into the beer as scavenged by the yeast. The downside of this is that you lose hop flavor and aroma as CO2 bubbles away, and you have to do fairly long dry hop which many people seem to think is not ideal.

An alternative raised in this thread is to hang your dry hops in the head space of your fermenter, let them sit there during active fermentation, and then drop them into the beer at the appropriate time. I have successfully done a trial run of this in my big mouth bubbler by having a hop bag suspended on a piece of thread running through an S airlock. This is sort of a PITA to set up but I can confirm it works fine; the bag will happily hang out indefinitely at the top of the fermenter, and I can drop it into the beer whenever I want without opening the lid.
As long as the hop pellets remain dry and intact I can't see much aroma being stripped from them.

I also do the magnet method when fermenting a neipa in my 30 liter Speidel. I use rare earth magnets, one outside, one inside (in vacuum-sealed bag). When it's time I slide the hops, (inside a hop sack), down into the beer, and can either leave them or slide them back up after x days if desired. It seems to work fine, and is probably the best solution for me given my setup. One thing I have not yet resolved is the bolded text from @McMullan about the hops remaining dry. My procedure is to use a pre-washed hop sack that I then soak in SS solution just prior to adding the hops inside. They do get a little damp this way. I thought if I SS the sack earlier, and then let it dry, wouldn't it then negate the benefit of sanitizing it? Or am I overthinking it?
 

RyPA

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Just to be clear, the way I'm doing this has the string running through the regular chambers of the S airlock, passing through the sanitizer. There's no additional hole.
Gotcha, I missed that part

@BongoYodeler That's pretty much exactly what I did, except I bought 6 rare earth magnets and vacuum sealed groups of 3, to give it more strength. The magnets held up enough to hold them outside of the beer for the first few days and to slide them into the beer at day 4 or so, but I was unable to get the hops back out of the beer. It was either the weight of the saturated hops + muslin bag, or maybe a little krausen was still there. I decided for my next batch to run CO2 from a floating dip tube, pop the lid and throw the hops in commando, seal it up, and then purge 10 or so times. Not ideal, but I have a feeling I am not getting good utilization when I pull out the hop bag after the keg is done, it's a bloated sack of sand, there's no way I am getting everything out of the hops this way.

I also considered getting some nylon bags or some nut milk bags, which are not as stretchy as muslin bags. When I was setting up the hop bag inside the keg before sealing it up, I had to retie the bag a few times to reduce the sag, it was really annoying.

The beer came out great until the final glass, but I feel like I should have had a little more hop character out of 12 oz of citra.

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McMullan

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I like the magnet in a vacuum sealed bag idea. Genius 👍 For sanitizing the hop bag why not microwave it for a few minutes?
 

RyPA

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IMO, soaking it in some sanitizer and then wringing it out good is fine, the bag being slightly damp isn't going to cause any issues.
 

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I stuff the muslin bag into an espresso coffee cup and pour about a 1/2 oz of vodka on it, just enough to get it thoroughly wet but not exactly dripping. So far that seems to have worked...

I should vacuum seal the magnets or do something similar, so far haven't bothered. It'd be safer if I did.

I have stuff suspended until about 2 - 3 days before I keg, that's when I drop them in. But I'm doing pale ales, if it was NEIPA's I might think differently. I'm using the same "tricks" right now for some nibs waiting to drop into a fermenting stout.
 

RyPA

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I stuff the muslin bag into an espresso coffee cup and pour about a 1/2 oz of vodka on it, just enough to get it thoroughly wet but not exactly dripping. So far that seems to have worked...

I should vacuum seal the magnets or do something similar, so far haven't bothered. It'd be safer if I did.

I have stuff suspended until about 2 - 3 days before I keg, that's when I drop them in. But I'm doing pale ales, if it was NEIPA's I might think differently. I'm using the same "tricks" right now for some nibs waiting to drop into a fermenting stout.
I'm going to condition an oatmeal stout on 3 lbs of coconut, 3oz cacao nibs, and 2 vanilla beans in a few days. I have a floating dip tube with a screen in my fermenter, planning to drop all 3 additions in commando, and then transfer to a keg a few days later. I'm thinking the floating dip tube screen will catch everything on the transfer to keg.

I'm popping the lid on the stout while running CO2 through the floating dip tube, and will purge a few times with CO2 before sealing it. Hoping I do not get oxidation issues. With CO2 being more dense, and the CO2 coming from the bottom up, this should push all of the O2 out from the bottom up.
 
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With CO2 being more dense, and the CO2 coming from the bottom up, this should push all of the O2 out from the bottom up.

It doesn't really work that way. O2 just mixes in, and very quickly. Otherwise we'd be walking around in a CO2 blanket on earth and have to climb mountains to find O2. Think of it more like dirty water / clean water mixing together.
 

McMullan

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Wind kind of helps mix things up in the atmosphere. Neither O2 nor CO2 are at fixed proportions in ambient air. It actually varies. The proportions noted in textbooks are just averaged. CO2 evolving from below is going to promote pressure and mass movement out.
 

kevin58

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I use one of these... a stainless hop tube that fits in a corny keg.
 

CascadesBrewer

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and vacuum sealed groups of 3, to give it more strength

Looks good! This is on my list of things to try. I tried the bare magnets, and was a little worried about the bare metal. I tried some stir bar magnets (with the rare earth magnets on the outside), but they do not grip very well. I probably need a little smaller that does not droop so much. Some people are using sous vide magnets, but I am not sure I want to throw another $20 toward this.

@josephort: Are you bottling or kegging? If bottling, there are probably bigger sources of oxidation there. Overall I like the approach you discuss. It seems like it should work as good as using magnets, and you don't have to spend the money on magnets.

I am at the point where adding dry hops is the only time I need to open my fermenter. I have had good luck just pulling off the stopper, quickly dumping in the hops, and putting the stopper back in place. Part of me wants a better setup where I can use CO2 to keep some positive flow as I add the hops.
 
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josephort

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@josephort: Are you bottling or kegging?
Kegging, and doing a fully closed transfer to boot. So the only oxidation risk comes from late dry hop additions, hence my convoluted string-and-bag strategy.

I just picked up yeast, grain, and 10 oz of Cashmere from my local Northern Brewer store. Will brew tomorrow and probably hang the bag once the Krausen starts to fall... will post a couple of pics when I do!
 

CascadesBrewer

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I just picked up yeast, grain, and 10 oz of Cashmere from my local Northern Brewer store. Will brew tomorrow and probably hang the bag once the Krausen starts to fall... will post a couple of pics when I do!

Good luck! I watched an NEIPA brew day from The Apartment Brewer (from Feb 23, 2020). The second dry hop addition would make a lot of people cringe. He opened the lid of a bucket, add a bag of hops, and then pushed it down into the beer with a long spoon. I am not sure what he did for keg transfers at that time. At least at the tasting, that beer seemed to have survived. Stuff like that make me wonder exactly how far we need to go to avoid oxidation.

I have tried a few times to add some crushed campden tablet with the dry hops. I don't have any thing conclusive to report, but I also have not had any negative issues. Some people report sulfur. I also picked up some ascorbic acid to play with as well.
 

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DarrellQ

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Looks good! This is on my list of things to try. I tried the bare magnets, and was a little worried about the bare metal. I tried some stir bar magnets (with the rare earth magnets on the outside), but they do not grip very well. I probably need a little smaller that does not droop so much. Some people are using sous vide magnets, but I am not sure I want to throw another $20 toward this.
I put a large washer in a small zip lock bag with the hops in a muslin bag and put the strong magnet on the outside of the Fermonster. Works great.
 

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I just received a set of Silicone Coated Sous Vide Magnets that I had ordered. They have a good strength and work with the hard drive computer magnets I plan to maybe use on the outside of my SS bucket. So I'll see how they work on an APA that's on deck next. As far as sanitizing them I'm not sure about acid or iodine but I did read silicone is micro-wave safe if not used on high. I'll report back on a followup.
Scratch the microwave thought, duh, not sure what type material the magnets are made of. I'll just use star-san.
 
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josephort

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Stuff like that make me wonder exactly how far we need to go to avoid oxidation.
Yeah, I definitely think a lot of this might be overkill. That said, when I have been less careful in the past I have noticed NEIPAs and other dry hopped beers significantly degrade due to O2 exposure, and I think I might be at greater risk than some others because I typically take several months to finish a keg. Suspending a hop bag is a little annoying and may or may not actually make a difference, but it's a pretty low-effort step to take for a bit of insurance. I'm not (yet) considering any of the more dramatic process changes that some people pursue in the name of LODO.
 

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It doesn't really work that way. O2 just mixes in, and very quickly. Otherwise we'd be walking around in a CO2 blanket on earth and have to climb mountains to find O2. Think of it more like dirty water / clean water mixing together.
Valid point. Maybe with letting out a decent force of CO2 from a floating dip tube, you will have an exerting force coming out of the fermenter, reducing the amount of o2 that can make its way in.
 

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Valid point. Maybe with letting out a decent force of CO2 from a floating dip tube, you will have an exerting force coming out of the fermenter, reducing the amount of o2 that can make its way in.

You can certainly flush the area with some CO2 and get the O2 out rather quickly. The water analogy - you have a bucket of dirty water, and add some clean water into it. The dirty water mix flows over the edges. After a while you end up with a bucket full of clean water, or of course very close enough to it.

That's not exactly how it works but is probably closer as a way to think of it.
 

RyPA

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The way I was thinking of it is suppose you have a garden hose with CO2 coming out of it, with a slight force. It would be difficult/impossible for any other gas to get in.

Similar thought process for having a decent CO2 load in the fermenter, it would come out of the top like smoke coming out of a chimney.
 

RyPA

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@josephort I'd say yes you want them fully submerged. This will improve the contact area of the hops/beer. If they are not weighted down, the bag will float, and the top of the hop sack will not be contacting beer.

I am considering throwing hops in commando for my next NEIPA, just trying to figure out the logistics to avoid o2 exposure
 
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josephort

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As promised, here's a photo of the setup I used:

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The sour cream container was necessary to keep the hop bag from dangling into the top of the beer. I cut a bunch of big holes in the bottom and weighted it down so it would sink quickly. Even with this little innovation, the whole thing was hanging closer to the krausen than I planned, and the hops at the bottom may have gotten slightly damp. This was partly because I wasn't able to keep the thread as tight as I wanted, so it's dangline a few inches below the top of the fermenter, and partly because I had slightly less trub loss than I expected so the beer line was a bit higher up than normal. I think having more headspace would've made this a lot easier- if I do this again I'll brew a slightly smaller batch.

I set this up as the krausen was falling and let it sit for several days, then lowered it yesterday. No problems there, the hop bag went straight into the beer.

I'll report back when I start drinking the beer. Overall though I'd say this is a totally viable strategy for anyone who wants to do late dry hops but is concerned about O2. Whether it's really necessary or actually improves the beer quality, IDK.

I do think using magnets could be less finicky than doing the string thing, but it would require pretty strong magnets and some way to seal them off from the beer, neither of which I have on hand. (rare earth magnets can corrode and leach toxins, apparently). If this beer turns out especially good, maybe I'll look into that for the next one.
 

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@scrap iron

I have used the magnets vac sealed and in a hop bag very successfully. They held very well with hard drive magnets ( rare earth ) on the outside, I have just got some sous vide magnets and plan to use these next time instead of the vac sealed magnets. Starsan for the bags and sousvide magnets for me.
If you didn't think that starsan would do the job you should be able to at least pasteurise in 80 C water or boil them as they are for sous vide cooking.

The great benefit I find as well as the closed aspect is you can drag the hops below the beer / wort level and also swish them about to stir up the wort and ensure it all mixes well, then remove them when you think they are done and let them drip into the beer.

@josephort I do pressure ferment my NEIPA after a few days, there's no way to hold the aroma in the beer when so much CO2 is produced I think about 400 litres for a 20 litre batch if memory serves me.
IMG_20201108_170431.jpg


Not a picture of an NEIPA by the way.
 

scrap iron

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@DuncB
I just brewed my APA Tuesday and used the sous vide magnets. Just put one inside the bag and soaked in a bucket with star-san. I tested them with another one on the outside and it seemed to hold well with my SS bucket. I'll see how they do with the hard drive magnets next time. I might try two sous vide next time in the hop bag and see if holds it out of the beer better. cheers.
 
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