Dry Hopping Science

[joenearboston]

According to this paper, hop aroma peaks around 24 hours with agitation:

http://ir.library.oregonstate.edu/xmlui/bitstream/handle/1957/34093/Wolfe_thesis.pdf?sequence=1

 

[mot]

If I have enough time I love dry hopping when fermentation is just barely going so you have some agitation but it sonething you have to monitor close, works great. i usually do short dry hops 2 or 3 days max and maybe twice.

 

[Heine81]

I read that paper as well. I'm interested to see how it works. I've got my stir bar set up for a stirred secondary dry hopping. I'll probably let some fermentation occur to fill up the headspace with CO2, and then stir for a few days, and then let everything settle for a couple of days. I'll let you know how it goes.

 

[BBL_Brewer]

Interesting read. Thanks for posting.

 

[mabrungard]

Unfortunately, the conditions modeled in that paper are not remotely representative of beer in a fermenter or bright tank. But one thing I take away from the paper is that the effect of dry hopping is likely to only require a short time. Matt Brynildson of Firestone Walker long ago recommended a short dry hopping time of 3 to 4 days. It looks like that recommendation is indirectly supported by the paper.

The bottom line...don't dry hop for long periods.

 

[mot]

Unfortunately, the conditions modeled in that paper are not remotely representative of beer in a fermenter or bright tank. But one thing I take away from the paper is that the effect of dry hopping is likely to only require a short time. Matt Brynildson of Firestone Walker long ago recommended a short dry hopping time of 3 to 4 days. It looks like that recommendation is indirectly supported by the paper.

The bottom line...don't dry hop for long periods.

Iusually do dry hop for 2-5 days but there is nothing wrong going longer than that. Sometimes I leave them in the keg as I serve it

 

[Randy_Bugger]

Table 6. Overall aroma intensity
Sample Overall Intensity
(panelist mean value)

Groups
Stirred, 4 days 9.432 A
Stirred, 12 days 9.227 A
Stirred, 24 hours 8.591 A B
Stirred, 6 hours 7.614 B

Passive, 4 days 5.750 C
Passive, 6 hours 5.545 C
Passive, 12 days 5.205 C
Passive, 24 hours 5.023 C

Interesting how a 6 hour passive dry hop provides a higher intensity than 12 days or 24 hours and a 6 hour stirred dry hop is more effective than anything passive.

 

[Heine81]

Randy - I agree, agitation seems to be key. I'm rigging up a stir bar in my dry hopping that i'm doing this week.

I'll report back the findings - here is my plan:

Rack to secondary with Dry hops in muslin bag (2oz, whole leaf chinook)
Wait 48 hours (let CO2 blanket develop over beer)
Turn stir bar on for 96 hours
Let everything settle for 48 hours, and bottle.

 

[PDX_T]

Ah the master's thesis. full of nuggets of n=3 wisdom. It looks to me like anything between 1 day and 6 is likely to produce the desired effect in real whole hop fermentations without impact to astringency. I'm taking this one to work with me though. My brewery could use the info on pellet hops. Thanks for the post!

 

[suregork]

Slightly related, I stumbled upon the following paper titled 'The influence of dry hopping on three different beer styles' in a recent Brauwelt International issue:

http://www.baywa.eu/fileadmin/media/relaunch/Downloads/.DE/Ackerbau/Hop_Sales_Article_Kaltner.pdf

The results aren't that remarkable, but what I found interesting was that (contrary to the common belief) dry hopping does in fact increase the concentration of alpha and iso-alpha acids in the beer (and thus increases IBU). The increase is quite small of course. What I also found interesting was that dry hopping seems to increase beer pH. I've been struggling with some high beer pH values lately (especially in the heavily dry-hopped ones), and it seems that the dry hopping might have at least somewhat contributed to it.

 

[gandelf]

TORPEDO! Sierra Nevada incorporates this process. I modified a whole house filter to include ball lock fittings. I use a spare march pump to recirculate the wort in a freshly kegged beer. I have been doing this for the past year and can confirm one day is sufficient. I use a spare keg with ~one pint of Starsan and pressurized with co2 to sanitize and then purge the filter, pump and lines. I do this at ~60 to 65 degrees (cellar). I do this to ALL my hoppy ales. For me, no other process comes close in producing flavor and aroma. I do use 2 to 4 ounces whole hops. An added bonus is the recirculation with whole hops filters some of the yeast out, producing very clear hoppy ales. Try it, you will not be sorry!

 

[GotPushrods]

TORPEDO! Sierra Nevada incorporates this process. I modified a whole house filter to include ball lock fittings. I use a spare march pump to recirculate the wort in a freshly kegged beer. I have been doing this for the past year and can confirm one day is sufficient. I use a spare keg with ~one pint of Starsan and pressurized with co2 to sanitize and then purge the filter, pump and lines. I do this at ~60 to 65 degrees (cellar). I do this to ALL my hoppy ales. For me, no other process comes close in producing flavor and aroma. I do use 2 to 4 ounces whole hops. An added bonus is the recirculation with whole hops filters some of the yeast out, producing very clear hoppy ales. Try it, you will not be sorry!

How do you feed the pump from a keg? Do you have a picture of your setup?

It sounds like you recirculate for 24 hours? Is this correct or did I interpret that wrong?

 

[ryan_george]

TORPEDO! Sierra Nevada incorporates this process. I modified a whole house filter to include ball lock fittings. I use a spare march pump to recirculate the wort in a freshly kegged beer. I have been doing this for the past year and can confirm one day is sufficient. I use a spare keg with ~one pint of Starsan and pressurized with co2 to sanitize and then purge the filter, pump and lines. I do this at ~60 to 65 degrees (cellar). I do this to ALL my hoppy ales. For me, no other process comes close in producing flavor and aroma. I do use 2 to 4 ounces whole hops. An added bonus is the recirculation with whole hops filters some of the yeast out, producing very clear hoppy ales. Try it, you will not be sorry!

I'd also like to hear more about this process!