I have been making pickled onions for years with no problems. I have recently bought pre peeled onions and find that in the pickle, these onions fizz in the jar.

Why is this - the onions look fresh and healthy?

  • 2
    How do you make your pickled onions? What do you mean by "fizz"?
    – logophobe
    Jul 7, 2018 at 4:58

2 Answers 2


The situation you describe sounds like natural Lacto-fermentation.

There are many airborne yeast around us all the time. Every culture on earth (no pun intended) has a some tradition of fermentation for storage purposes. It would seem that you have just the right conditions for that to occur.

This can be a good thing. It creates a product with properties than many find healthful. A few resources are here:

Red Onions

More Red Onions

Same principle for white onions. If you submerged the onion goodness you have going on with a clean disc of some sort you can finish the fermentation and have a yummy condiment !


What you describe is "fermentation" and what you have accidentally created is indeed onion cider. ;-)

It'll be very hard to deduce the exact root cause for this particular batch with the information we have but maybe:

  • you baked bread while pickling your onions and one speck of yeast was caught in your brine after it was boiled.
  • the onions were stored near a broken pack of dry yeast in the shop and not washed/sterilized thoroughly before being put in their jars
  • one speck of yeast landed in just one jar as the window was open while you were cooling down the jars with their lids off and all the others are fine.
  • ...

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