About 10 days after transferring a cider to secondary, it developed a faint diacetyl aroma. I moved it to a warmer location (~70degF) for a few days for a diacetyl rest, but the smell is now more pronounced.

I am considering the following next steps:

  1. If it is from bacteria, I am considering shocking it with campden and adding fresh yeast and a little sugar to allow the yeast to metabolize the diacetyl.

  2. If it is from the yeast, I will give it more time unless there are other recommendations.

  3. Toss it if it is beyond repair. Diacetyl is the dominant aroma.


Yeast: Lalvin D 47

OG: 1.045

Cider: Pasteurized

Temp: 60 to 65degF

Two other batches started at the same time and temperatures but with different yeast (Nottingham Ale and Mangrove Jack M02) have not developed the issue.

  • 3
    I don't have a great answer- but don't dump a cider unless it's truly bad after like...a year. D47/Montrachet aren't my favorite for cider, they take a while to clean up and have an odd profile. Sit & forget and try it in another month or two (if you have the space to do so). Sometimes they clean up and leave a really neat complex cider... and sometimes they're better ran through a still.
    – rob
    Nov 22, 2021 at 21:33

1 Answer 1


Diacetyl is a normal part of most fermentations. Nice thing is that yeast will eat it. The yeast just needs time. Give it 3-4 weeks of age, and the diacetyl should be cleaned up. No fancy actions are needed, just patience. If 4 weeks doesn't do it, wait a couple more weeks. Keep the cider at a reasonable temperature, upper 50s to 70 F will work just fine. When the diacetyl disappears, enjoy.

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