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Thread: Warm dry hopping and diacetyl

  1. #1
    Join Date
    Apr 2014
    Location
    AUS
    Posts
    140

    Warm dry hopping and diacetyl

    Hi people,

    We have had first hand experience with warm dry hopping, 21C, and diacetyl problems in our heavy hopped beers. We would typically see a beer finishing at 1.014, day 7, and after the dry hop sit at 1.010, day 11. We would crash the beer at this point. We started dry hopping at 16C after a negative forced diacetyl test and reaching our forced fermentation target, day 6. We will then crash the beer at day 11. We would not see any significant drop in gravity and the diacetyl issue got resolved.

    We did find that our hop profile was a little different due to dry hopping at a slightly cooler temp. My questions are the following:

    1) What does other brewers do to successfully dry hop at a warmer temp?
    2) Would you still have some biotransformations happening at 16C?
    3) Would it help to mash at a low temp to favour Beta-amylase so that refermentation doesnt restart after a warm dry hop
    4) If you see a dry hop creep at a warm temp, do you just leave it until your gravity is stable and a negative forced diacetyl test (if that is possible due to a lack of yeast since most of it has flocced out?)

    Cheers
    Last edited by Gbbc; 05-29-2018 at 03:05 PM.

  2. #2
    Join Date
    Aug 2018
    Location
    Berlin, Germany
    Posts
    3
    Hi there.

    Is that still your standard process to deal with it? We see the same behavior. I would be worried you still have enzyme activity in your beer but you just don't see the fermentation because the temperature is too cold and you removed most of your yeast. Then you would package your beer with fermentables left and see the fermentation in cans / kegs.

    Cheers

    Lukasz

  3. #3
    Join Date
    Oct 2002
    Location
    Chesterfield, UK
    Posts
    1,786
    You are adding oxygen to the beer, entrained in the hops. You need to get rid of the bulk of the entrained air before adding to the beer. Lots of discussions about dry hopping methodology on this site
    dick

  4. #4
    Join Date
    Jun 2011
    Location
    Richmond, VA.
    Posts
    429
    if have had issues with ringwood throwing out diacetyl if dry hopped to early. I used it in an american ipa. 3 day fermenting under temp, turned off the glycol for 7 more day. I would crop as much yeast as possible then dry up for 7 day before cold crashing. some might say it is too long but i am ocd with it.

  5. #5
    Join Date
    Aug 2018
    Location
    Berlin, Germany
    Posts
    3
    Hey there.

    I think the 2nd fermentation here comes from "hop creep". We use wy1272 pitch at 17 C / 62 F, go up by 1 C next 2 days and let it free rise at 50 % attenuation. We do FFT to see which FG we can expect. When we are at FG we leave it for a couple days there till D is gone. We harvest and/or remove the yeast. Then we dry hop warm. We use a HopGun which should not introduce too much oxygen. After DH (15-25 g/L = 4-6 lbs/bbl) the beer starts fermenting again and attenuates way more then the FFT. We can see D in the beer then in our VDK test (heat+chill). It does not really seem to go away completely. I guess there is some acetolactate left and when we introduce some oxygen when we send it to our centrifuge and a BBT it can potentially turn into D.

    We think the 2nd fermentation happens when the hop enzymes chop starch and dextrins into glucose in the FV which the yeast starts fermenting again. It seems breweries that dry hop at 16 C / 60 F after dumping the yeast don't see that phenomenon. But I wonder if the enzymes are still active but you just don't see any fermentation in that short time at such a low temperature. I would be worried it starts fermenting in the cans on some warm shelve and produce D or even explode. We see gravity drops of like 1 P after DH in the FV.

  6. #6
    Join Date
    Jan 2013
    Location
    North Carolina
    Posts
    84
    When you see drop of 1p does it stop after? We see slow creep for awhile sometimes, often wonder if it is completely done or if it will continue at warm temps. We dry hop low 60s but i wonder about cans on warm shelves. Currently we just sell in the tap room.

  7. #7
    Join Date
    Aug 2018
    Location
    Berlin, Germany
    Posts
    3
    I can't tell if it really stops. Sometimes we see gravity drop one day after DH. Sometimes it starts 2 days later. It seems to finish in like 3 days. It seems to stay stable after that. Then we crash it. But to be honest I don't know if it wouldn't start fermenting again. We only keg our beer and ship it around europe. The beer seems stable. But I am still a bit worried how it would do in cans.

    Btw. Last week we chilled the cone for harvesting. We forgot to switch off the glycol and it chilled the beer to 16 C. So we dry hopped at that temperature and there was no fermentation the next few days. Then we did heat it up to 19 C and it started fermenting.

  8. #8
    Join Date
    Apr 2018
    Location
    Kentwood, MI, USA
    Posts
    5
    You are right that it is an enzyme that is converting after dry hopping. FPH (Freshening Power of Hops) is the phenomenon that you are seeing. Colleagues of mine at Bell's Brewery did some research into this and have recently published a paper on it. They believe that the enzyme in hops is a type of amylase that is causing the creep. We observe the same thing here but we centrifuge our dry-hopped products bright to extract the yeast so that fermentation doesn't restart in package. If you are just dumping yeast, dry-hopping, dumping hops, and packaging then you have to worry about bottle bombs or cans exploding.

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