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When I've read kombucha recipes a last recommended step was to bottle the liquid, allow some gas buildup to carbonate it, and then refrigerate it to stop the bacteria from continuing to produce gas. My understanding is that if you just left the kombucha at room temperature in a sealed bottle the bottle would eventually break or explode.

I'm now making vinegar instead of kombucha, and based on the few recipes I can find it seems to me that it is safe to seal the vinegar in a bottle but that's only because the recipes haven't told me specifically not to.

Is homemade vinegar safe to store in a sealed bottle at room temperature? With both kombucha and vinegar I start with a sweet mixture which I leave out for some time, and I understand that both should have some amount of both lactic and acetic acid producing bacteria to different degrees. I believe the answer should be yes because the vinegar contains primarily acetic acid bacteria but I would appreciate a confirmation and a bit of an explanation on the process. It seems to me that in bottling it I'm just gambling that I have one type of bacteria and not the other. I'd think the store bought unpasteurized stuff could be tested before being bottled to check this.

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  • Just a personal update: the vinegar I'd made was definitely not finished fermenting and definitely not safe to store sealed long term. After one night there was some pressure build up in the bottle and it bubbled quite a lot after I opened it. To any other vinegar newcomers, be more patient than me! What I've got tastes great already though.
    – qfwfq
    Sep 4, 2021 at 20:18

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If you are sure, that there is no sugar left in your vinegar, then the answer is yes. https://www.urbanfermentation.com/how-to-store-homemade-vinegar/

Acetic acid bacteria use O2 to convert alcohol. If the bottle is closed and they used up the O2, the fermentation stops. Even if there is some air in the bottle when you seal it, the pressure build-up caused by AAB should be negligible. It is recommended to put the vinegar into smaller bottles when there is too much airspace, but only because the AAB starts to break down the acetic acid into water when there is no alcohol left(again using the O2).

The yeast however can work anaerobically (for reproduction it needs O2, but to produce alcohol, no oxygen is required). So if there is some sugar left, the yeast can build up some pressure by producing CO2. Also the lactic acid bacteria. This means, you have to make sure that there is no sugar left in your vinegar:

  • either by fermenting for a long time
  • or by checking the sugar content

I start the AAB fermentation only when the alcoholic fermentation has quasi stopped. At this point the simple sugars are consumed, only some complex sugar are left - these take a long time to be converted to alcohol, but there is not enough of them to cause real trouble.

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  • That link is extremely helpful, I hadn't found that page. One question: "I start the AAB fermentation only when the alcoholic fermentation has quasi stopped" how do you personally know that it has stopped? Saw a couple methods in the urban fermentation page, just curious how you do it
    – qfwfq
    Sep 4, 2021 at 20:15
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    I always use a bottle for the alcoholic fermentation with a water filled stopper. When the bubbling stops/slows down enough that I don't notice it, I consider the fermentation finished.
    – G. B.
    Sep 5, 2021 at 6:12

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