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Dry hopping: do I purge with CO2?


read 2698 times • 19 replies • posted 8/5/2012 12:18:13 PM

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sharpe1987 8:
I am dry hopping in my primary fermenter without racking to a secondary vessel. Primary has gone for seven days. When I add my dry hops should I purge with CO2 to keep from oxidizing, or will this addition of CO2 kill all the active yeast still cleaning up the beer?
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SpringsLicker 3169:132
No need to do anything. In my experience the fermentor should have a blanket of CO2 on top of the beer and youíll be pouring the hops through that layer down into the beer. What little possible loss of CO2 that occurs from the hop addition will be replaced by CO2 that is in solution and releases from the action of the hops being dropped in there. CO2 doesnít kill yeast.
8/5/2012 1:03:22 PM

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bitbucket 2159:63
Originally posted by sharpe1987
will this addition of CO2 kill all the active yeast still cleaning up the beer?

Nope. Yeast produce CO2, so theyíre used to it.

I guess you could flood the fermenter with a bit of CO2 after youíre added your hops if you believe youíve stirred up the existing CO2 blanket, but after seven days the yeast will probably still be working a bit so it should be replenished anyway.

This is a level of detail Iíve never worried about, and Iíve not had any noticeable oxidization in my dry-hopped beers.
8/5/2012 3:56:27 PM

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oteyj 2130:14
Donít worry about it. Just put them in expediently and close the fermenter back up. After primary, there should be primarily CO2 in the fermenter. CO2 is heavier than O2 so the O2 from the hops will rise to the top.
8/5/2012 3:58:46 PM

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SamGamgee 2452:182
I agree with the above posters. Part of the beauty of dry hopping in primary is that you donít need any extraneous CO2. If you were racking to a secondary vessel, then yes, you should purge it with CO2 before transfer.
8/5/2012 9:33:20 PM

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sharpe1987 8:
Awesome. I wonít waste a whole CO2 cylinder on the little CO2 it would refill.

Next question, has anyone experienced a difference in dry hopping while still on the yeast in the primary vs. racking to the secondary? Iíve heard the guys at Sierra Nevada prefer to dry hop on active yeast. Just not sure why.
8/6/2012 7:11:35 AM

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SpringsLicker 3169:132
Originally posted by sharpe1987
Awesome. I wonít waste a whole CO2 cylinder on the little CO2 it would refill.

Iíve heard the guys at Sierra Nevada prefer to dry hop on active yeast. Just not sure why.


Not sure why either, but I donít think it will matter much. How long you dry hop, whether you use pellets or whole leaf hops,the variety and freshness and the temperature that you fermenting are all more important as a home brewer. Keep in mind that a lot of the procedures that commercial breweries employ are profit based, not quality based.
8/6/2012 7:29:52 AM

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SamGamgee 2452:182
Originally posted by sharpe1987
Awesome. I wonít waste a whole CO2 cylinder on the little CO2 it would refill.

Next question, has anyone experienced a difference in dry hopping while still on the yeast in the primary vs. racking to the secondary? Iíve heard the guys at Sierra Nevada prefer to dry hop on active yeast. Just not sure why.


We like to dry hop while there is still active yeast in solution, which means adding hops before you finish fermentation, and doesnít really have anything to do with transfering to secondary or not. The yeast sitting on the bottom of the carboy is done working and isn;t what you want to worry about, itís the yeast still up in the beer that is going to have an effect.

Basically, if you want to dry hop while there is still activity, you have to do it early, like day 4-5, though it really depends and youíre probably only going to get it right with repeated fermentations of the same beer. Too early and you loose a good amount of your hop oils to the yeast, and too late and you miss out on that amount of hop/yeast interaction that is the whole point of dry hopping at this time.

What the yeast does is it takes some of the aromatic compounds in the hops and changes them into new compounds. You can get some different fruity notes from doing it this way that you donít get if you wait until fermentation is done and most of the yeast has dropped out.

Even if you time it right, you still do lose more aroma to yeast absorption than if you were to wait. THe best way around this is to add half your hops early to get some of this effect, and then add the other half in 2-3 days to get more of the punch from some of the oils that you are going to miss out on from the early addition. At this point it might be good to do it in a secondary carboy that you have added the second hop addition to and then purged with CO2, or you could just do it gain in primary. Never done it this way in carboys though, inly in conicals where its easy to dump the first addition off of the cone before adding the second.

Just always remember that oxygen is probably the biggest enemy of hop aroma at this point, so be careful.
8/6/2012 8:34:54 AM

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SamGamgee 2452:182
And as far as sierra nevada goes (donít know if what you said about them is true and have never heard that myself), they use whole hops and dry hop by recirculating beer through a small vessel called a "torpedo" which allows them to get good extraction of hop oils in a smaller amount of time via mechanical action.

On a large scale, itís very hard to steep with whole hops because it takes much longer and itís hard to get good contact with the beer if they are in hop bags, which is what they used to do. Thatís why the overwhelming majority of breweries use pellets for dry hopping. you just add them to the top of the tank and most settle in the cone within several days and can be dumped off the bottom. Since the lupulin glands have been mostly ruptured during the pelletizing process, maximum oil extraction can occur in under a day and you donít really get much from having them in for more that 3 or so days anyway (at ale fermentation temps anyway, colder temps means longer extraction times).
8/6/2012 8:41:03 AM

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sharpe1987 8:
Last question (maybe). As I said before, Iím dry hopping in the primary. Should I shake the carboy a bit to get the newly added hops into solution better and stir up the crud on the bottom? Or just drop them
In and let it go?
8/6/2012 8:48:02 PM

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Erlangernick 1:2
Originally posted by SamGamgee
And as far as sierra nevada goes (donít know if what you said about them is true and have never heard that myself), they use whole hops and dry hop by recirculating beer through a small vessel called a "torpedo" which allows them to get good extraction of hop oils in a smaller amount of time via mechanical action.

On a large scale, itís very hard to steep with whole hops because it takes much longer and itís hard to get good contact with the beer if they are in hop bags, which is what they used to do. Thatís why the overwhelming majority of breweries use pellets for dry hopping. you just add them to the top of the tank and most settle in the cone within several days and can be dumped off the bottom. Since the lupulin glands have been mostly ruptured during the pelletizing process, maximum oil extraction can occur in under a day and you donít really get much from having them in for more that 3 or so days anyway (at ale fermentation temps anyway, colder temps means longer extraction times).


Repeating an age-old question: But doesnít pelletising also destroy some aroma? Use more to compensate?
8/7/2012 12:37:04 AM

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