Hop aroma disappeared after closed transfer

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natesky

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Hi there! This is my first time posting here. I recently brewed a double IPA (my first in this style), which included a hefty dry hop dose (Simcoe, Centennial, and CTZ - about 7 oz in total).

I knew that oxidation could be an issue, so I went ahead and fermented in a 6 gallon keg (5.5 gallons of wort). It was completely closed to outside air except for the 20 seconds or so it took to add the dry hops (post fermentation) - this was done with the gas running at ~2 psi the whole time to keep as much oxygen out as possible. After the dry hops were in, I purged another several times to clear the headspace and raised the pressure to 10psi. After 2 days, the beer tasted and smelled great! I did a closed transfer to another keg (purged with CO2/starsan), and immediately (the transfer took ~30 minutes), all hop flavor and aroma was gone!

I don’t think oxygenation can take place in less than an hour (can it?). Is there something in the process of a closed transfer that could strip the flavor and aroma away? Both the fermenting keg and the serving keg had FLOTit 2.0 floating dip tubes with mesh filters. The serving keg had been well washed before being purged with starsan & CO2.

I’m truly at a loss here. Has anyone else ever experienced something like this?

I can give more information, but the key issue is that before the closed transfer to a purged keg, it smelled and tasted great. Afterwards (30 minutes later), all aroma was gone. Any help is appreciated!
 

Elric

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Did you do a true closed transfer or were you venting gas from the receiving keg to get the beer flowing in? If you were venting it than you were letting out any potential aromatics that were in the headspace of the initial keg from the dry hop. Your multiple head space purges after adding your dry hop would have also driven off any hop aromatics that were in the headspace from initial phase of fermentation as well which again would leave you with less to carry over to the new keg.
 

marc1

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Hi there! This is my first time posting here. I recently brewed a double IPA (my first in this style), which included a hefty dry hop dose (Simcoe, Centennial, and CTZ - about 7 oz in total).

I knew that oxidation could be an issue, so I went ahead and fermented in a 6 gallon keg (5.5 gallons of wort). It was completely closed to outside air except for the 20 seconds or so it took to add the dry hops (post fermentation) - this was done with the gas running at ~2 psi the whole time to keep as much oxygen out as possible. After the dry hops were in, I purged another several times to clear the headspace and raised the pressure to 10psi. After 2 days, the beer tasted and smelled great! I did a closed transfer to another keg (purged with CO2/starsan), and immediately (the transfer took ~30 minutes), all hop flavor and aroma was gone!

I don’t think oxygenation can take place in less than an hour (can it?). Is there something in the process of a closed transfer that could strip the flavor and aroma away? Both the fermenting keg and the serving keg had FLOTit 2.0 floating dip tubes with mesh filters. The serving keg had been well washed before being purged with starsan & CO2.

I’m truly at a loss here. Has anyone else ever experienced something like this?

I can give more information, but the key issue is that before the closed transfer to a purged keg, it smelled and tasted great. Afterwards (30 minutes later), all aroma was gone. Any help is appreciated!
How did you purge with starsan and co2?
 
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natesky

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Thanks for the replies! To answer (in reverse order):

How did you purge with starsan and co2?
I filled the serving keg completely with starsan, and then connected the liquid line to the liquid line of another (completely empty) keg. I then hooked up the gas line of the starsan-filled keg to the gas post of the fermenting keg (at high krausen). In all, it took about 2 hours to completely push the starsan out of the keg (and into the empty one) using the CO2 the yeast were putting out.

Did you do a true closed transfer or were you venting gas from the receiving keg to get the beer flowing in?
I connected the liquid lines of the fermenter-keg and the purged (empty) keg, and I hooked up the gas line of the purged keg to another starsan filled keg (I figured I'd use that CO2 to purge another keg, as well). I then hooked the gas line of the fermenter-keg to the CO2 tank and put about 2 psi of pressure on. It took about 20 minutes to transfer. I think that means I was venting, yes?

If you were venting it than you were letting out any potential aromatics that were in the headspace of the initial keg from the dry hop.
I hadn't thought of that. I'm not sure I understand 100% - if I only transfer the liquid from the fermenter-keg to the purged serving keg (I stopped the transfer as soon as gas started flowing through the lines), the only gas I would be venting would be the CO2 that was already in the purged keg, right? Not the gas in the headspace of the fermenter. Do people usually try to transfer some of the CO2 along with the beer in order to get the "headspace" gas in, as well? This is my first time doing a transfer like this, so forgive me for asking.

Your multiple head space purges after adding your dry hop would have also driven off any hop aromatics that were in the headspace from initial phase of fermentation as well which again would leave you with less to carry over to the new keg.
That's a good point - I can see how that could reduce some of the aromatics. Still, the sample I took just before I started the transfer tasted great - so I assume any loss of flavor from a few days before when I added the dry hops would have been apparent then, right?
 

Elric

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As you transfer from fermenter to keg aromatics will be coming out of the beer just as if you were pouring a glass, In a closed transfer you have close to equalized pressure and as it is under pressure and denser than atmospheric pressure, what is bleeding out is only a portion of the aromatics from the beer. What remains under pressure will stay in the keg and some may reequalize into the beer after you put keg under further pressure. When you are venting from the keg, you are at regular atmospheric pressure and you are effectively getting rid of everything aromatic that is coming out of solution as you fill the keg. If you smell the other keg in the line or the air coming out of it, any aromatics you are getting are aromatics that are no longer in your beer.

There could be other factors here as well, that's just one possible one that stuck out to me.
 

agentbud

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Did you do a true closed transfer or were you venting gas from the receiving keg to get the beer flowing in?
I'm not sure I follow this. If the receiving keg has been purged using starsan and CO2 and you are doing a closed transfer to it, wouldn't you have to vent? As the beer goes in, something has to go out, right? How do you do a "true closed transfer" without venting?
 

PCABrewing

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Still, the sample I took just before I started the transfer tasted great - so I assume any loss of flavor from a few days before when I added the dry hops would have been apparent then, right?
Is it possible that the hops happened to be located close to the floating pickup when you drew your sample and therefore you got a good bit of the oils.
If that happened and your hop bag didn't really allow much circulation through the hop mass, perhaps the majority of the hop flavor stayed in the bag.
Just a guess.
 

tracer bullet

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FWIW I am in the same boat. After kegging, doing my best (which I swear is quite good), I still lose flavor over the first few days. After that though, it's still pretty good and maintains a long time. And I'd say it's every bit as good as almost anything I've ever bought in a can or bottle. So I don't beat myself up too much.

I'd love to keep the taste from the first few days but it might be a dream. There might be some chemistry happening that simply can't be avoided? Maybe the yeast is falling out and that's part of what I taste?

I CAN say for sure that by doing thoughtful closed transfers, swapping to EVA barrier lines, and so on that the flavor I get after 2 - 3 days maintains quite steadily after that (it did not used to, it used to continue to decline until after about a month it was just bland bitter fizzy yellow water).

Anyhow, you're not alone. I'd love to keep that flavor form the first few days as well. This might be where you have to get into serving from a keg that was also fermented in? If the flavor doesn't stay with that method, it ain't ever going to happen.
 

Elric

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I'm not sure I follow this. If the receiving keg has been purged using starsan and CO2 and you are doing a closed transfer to it, wouldn't you have to vent? As the beer goes in, something has to go out, right? How do you do a "true closed transfer" without venting?
A true closed transfer (or perhaps it would be more appropriate to call it a closed-loop transfer) means nothing is lost between the two vessels.
you have a fermenter let's say it is at 15 psi. To do a closed-loop transfer, you would have your keg purged and pressurized to 13psi. You would place the fermenter in such a position where the bottom of the fermenter is higher than the top of the keg. You would have a gas line and a beer line. The beer line would connect from the beer out on the fermenter to the beer out on the keg. You may get a bit of transfer when they connect, but likely not. The gas line would connect from the gas in on the fermenter to the gas in on the keg. Once this is connected the 2psi pressure differential between the two would start a transfer, and the force of gravity should keep it flowing when the differential eventually equalizes.
With this procedure once the transfer starts, no additional outside co2 is being added to the process to dilute any volatile aromatics.
 

eric19312

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sounds like a pretty solid procedure to me. The venting the headspace and closed loop vs merely closed are not going to explain the loss you are describing. I used to do open transfers and got good beer with clear hop aroma. Heck even open transfers into bottling bucket and then into bottles can make beer with decent hop aromas. With far less dry hop than I use these days. Yes they could have been even better but the hops were there.

How long did you wait after dry hopping to keg? Perhaps when you took that sample there was a slick of hop oil sitting on the beer that you disproportionately grabbed with your floating dip tube. I'm also wondering if the beer post kegging was cold or carbonated. Cold reduces flavors, carbonation pushes the aroma into your face, so if your sample was cold but not yet carbonated...be curious how this comes across in another week.
 
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