Apologies if this is a duplicate - wasn't able to find anything similar.

Making a 3gal batch of strawberry wine. Poured sugar-water over fruit and set aside to cool. Been having problems with bugs so I put the lid tight on bucket. Anyway, life got ahead of me and forgot about the wine for two days. Ran back to my bucket, opened the lid and was very surprised to see that the fruit had started fermenting without me! Strawberries were clearly into primary fermentation already. Fearing I would lose the wine, I added my yeast. 2 days later and things seem to be okay; primary is still going strong and must seems to be happy.

In doing research, it appears I stumbled into "young country wine" making, but all of the directions say to leave the bucket uncovered. My lid was tightly-closed, creating a secondary-like environment.

I've read there are natural yeasts on the fruit and in the air, but I removed the air.

Question Can anyone explain what happened?

  • Even though your lid may be airtight, that only keeps more air out. There's already air inside the bucket, unless you purged with inert gas, and that air could contain wild yeast. Also as you mention, fruit could harbor microbes and you didn't remove that. It would be helpful to know more about the process (were the berries fresh or frozen? Were they ever boiled?), but it does sound like you've got some spontaneous fermentation going on. Apr 3, 2015 at 15:25
  • @FranklinPCombs The berries were fresh and washed before the stems were cut out. The fruit was not boiled; it was kept at room temperature. The bucket was not purged; I just put the lid on, so I must have trapped some air in the 1inch headway I had between the must and the lid. Apr 3, 2015 at 21:17
  • Makes sense. see @TobiasPatton 's answer, in that case. Apr 3, 2015 at 21:19

1 Answer 1


All fruit has naturally occurring yeast on the skin. This is almost certainly why your strawberry wine starting fermenting spontaneously. Some winemakers (but not me!) prefer to let the wild yeast on the grape skins ferment the juice.

More information here.

  • And it's possible with a small about of trapped air (say an 1inch between the must and the lid)? Apr 3, 2015 at 21:19
  • 2
    The air is not important. The yeast is on the fruit. Apr 3, 2015 at 23:10

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