Recirculating Dry Hops for More Aroma Oil Extraction

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Recirculating Dry Hops for More Aroma Oil Extraction

Postby ocluke on Thu Feb 14, 2013 3:44 pm

I recently posted a blog write-up on my dry hopping setup, and I thought I would post it here for the Brewcommune crew as well. I welcome any thoughts, questions, criticisms, etc.
http://www.metabrewing.com/2013/02/recirculating-dry-hops-extract-more.html
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Re: Recirculating Dry Hops for More Aroma Oil Extraction

Postby bwarbiany on Thu Feb 14, 2013 4:04 pm

Great stuff!

One thing is missing -- tasting notes! Do you have any beers ready that used this method?

Something I do see that I can take away from this is that typically I've dry-hopped for 7-14 days. I've been told that maximum flavor/aroma extraction tends to occur more quickly than that, but I've just relied on tradition rather than science. It seems based on the graphics that you posted from the thesis (which I need to fully read) that the science is clear -- Using non-agitated pellets (my current method) will fully extract in 24-48 hours, and likely less.

So I can turn my beers faster :-)
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Re: Recirculating Dry Hops for More Aroma Oil Extraction

Postby BrewMasterBrad on Thu Feb 14, 2013 4:41 pm

Interesting read for sure. I did not take time to read the 92 page thesis. I have For the Love of Hops book, but have not had a chance to read it yet.

My one concern using any sort of post-fermentation agitation is the introduction of oxygen into the finished beer. I don't dry hop that often, but I am brewing an IPA on Monday that I will be dry hopping just letting the beer rest on loose pellet hops for 5 to 7 days at room temperature. I am sure it is probably mentioned in the thesis, but another factor of hop aroma extraction would be the temperature of the beer during dry hopping. I seem to remember reading somewhere about a sliding scale based on contact time and temperature.

I have been using the whirlpool addition method of adding hop character to my Pale Ales. Right after the boil, I add a significant amount of hops to the whirlpool before I start chilling. I allow the hops to whirlpool hot for about 30 minutes before I start chilling. This extracts a large amount of aroma and flavor from the hops since the wort is still hot, but since it is not boiling, those flavors and aromas do not flash off. There are three main advantages to using this technique. First, I don't have the additional time needed for dry hopping, so my beer is ready to drink sooner. Second, I don't have issues with additional transfers that may introduce oxygen or bacteria into the beer. Third, any oxygen that is introduced to the wort during this extended whirlpool will be scavenged by the yeast. On the downside, it takes a large amount of hops to accomplish the best results. Also, some of the hop character will be scrubbed out by CO2 during fermentation, so it takes some experimentation to the get the recipe dialed in.

I do have one question. You mentioned boiling your tubing to sanitize, but how do you sanitize your pump?
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Re: Recirculating Dry Hops for More Aroma Oil Extraction

Postby ocluke on Thu Feb 14, 2013 5:08 pm

My one concern using any sort of post-fermentation agitation is the introduction of oxygen into the finished beer.

Yes, that is a major concern. If you read the thesis, the steps they used to avoid this is well outlined. You need to be using a closed system when agitating. I open the blowoff bung on the top of my fermentor, add the hops, purge the hole with more CO2 (just in case any O2 got in when adding the dry hops), then quickly replace the blowoff bung. For the pump and hoses, I purge the pump and hoses with CO2, connect them, then let the beer bleed out of the racking arm through the pump until it is primed. Any remaining air in the line that might go into the beer is CO2.

I am sure it is probably mentioned in the thesis, but another factor of hop aroma extraction would be the temperature of the beer during dry hopping. I seem to remember reading somewhere about a sliding scale based on contact time and temperature.

All dry hopping in the thesis was at 73.76°F. Dry hopping temperature wasn't part of the experiment, so that's a whole different subject.

I have been using the whirlpool addition method of adding hop character to my Pale Ales.

I do this for all of my hoppy beers as well, but it doesn't replace dry-hopping, in my opinion.

I do have one question. You mentioned boiling your tubing to sanitize, but how do you sanitize your pump?

You can sanitize your pump by recirculating boiling water through it for a period of time. However, I actually don't do that with this pump very often. After disconnecting it from the conical, I rinse it very well with hot water, let it soak in hot PBW solution, rinse it, sanitize it, and then cap it and store it for the next use.
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Re: Recirculating Dry Hops for More Aroma Oil Extraction

Postby ocluke on Thu Feb 14, 2013 5:25 pm

One thing is missing -- tasting notes! Do you have any beers ready that used this method?

Good point. I have 2 beers on tap and one fermenting that use this new process. The results are excellent. I typically recirculate for 10 minutes on/15 minutes off, for 24-48 hours, then I dump the hops, cold crash, and rack.

I haven't done a controlled experiment with a beer that's dry hopped conventionally, but I hope to at some point in the near future.

Something I do see that I can take away from this is that typically I've dry-hopped for 7-14 days. I've been told that maximum flavor/aroma extraction tends to occur more quickly than that, but I've just relied on tradition rather than science. It seems based on the graphics that you posted from the thesis (which I need to fully read) that the science is clear -- Using non-agitated pellets (my current method) will fully extract in 24-48 hours, and likely less.

I guess the only way to know would be to do a sensory test for yourself. I recommend reading the thesis. It's not light reading, but it's informative. I was going back and forth with Peter Wolfe over email when I was designing my system, and he gave me the poster below that he created for a conference. It's a summary of the paper.
https://docs.google.com/file/d/0BwbtWo2etnesZzNDVFRpVGhrUU0/edit?usp=sharing
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