Diacetyl well after bottling and carbing

Discussion in 'Beginners Brewing Forum' started by Brewer #335694, Nov 3, 2020.

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  1. Brewer #335694

    Brewer #335694 New Member

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    I’ve made about 15 batches at this point...all have come out fine after bottle conditioning. Nothing amazing but well carbed and flavorful. But with a few of them there has emerged that buttery diacetyl off-flavor, BUT it has been several weeks down the line after bottle conditioning. In other words, for the first couple weeks after the beer has been carbed and ready for drinking, they tasted great. Then I would open one a week or two after that, and I sensed that buttery off-flavor. Why would it come on so late? Are the other flavors of the beer possibly dulling so now that is coming through? Does further bottle conditioning by the leftover yeast start to create that eventually? So odd.
     
  2. J A

    J A Well-Known Member

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    Diacetyl comes form two sources. Fermentation produces plenty of it but it's consumed as yeast "cleans up" metabolic compounds. The other source, usually responsible for "secondary" diacetyl production is bacteria. Somewhere in your system you've got a piece of equipment slightly infected or your bottles aren't being cleaned thoroughly. Usually secondary infections manifest in sour off flavors or bottle-bombing re-fermentation but diacetyl, is definitely a possiblity. Diacetyl as a bi-product of fermentation is usually palatable unless it's really intense. The diacetyl from infection is usually pretty offensive and noticeable.
    You haven't noted what sort beers you're brewing and yeast choice/ fermentation temp could be contributing, but I'd be inspecting equipment (buckets, spigots, tubes, bottles, etc and anything plastic or rubber) and cleaning or replacing everything that's a possible source.
     
  3. Brewer #335694

    Brewer #335694 New Member

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    thanks. Both times it was with the blondes that I made (one extract, one an all grain). The other styles, ipa, porter, Belgian triple it wasn’t noticeable. They ferment in my basement which had been maintaining around 69-70. And with 05 ale yeast.
     
  4. J A

    J A Well-Known Member

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    Makes sense that it would show up in the blondes and especially after they "lager" for a while and clear extra yeast flavor. US-05 isn't a suspect for diacetyl and your temps are high enough that any yeast will be fine. Acetaldehyde is a bigger problem at higher temps and diacetyl is rare.
    Definitely check your system for sanitation issues. It's a pretty common cause of funky diacetyl off flavor.
     
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