white yeast/mold/what on surface of vinegar

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white yeast/mold/what on surface of vinegar

Postby lgarrett on Wed Sep 06, 2017 10:23 am

I have a couple of batches of fruit scrap vinegar going. One all tomato scraps, the other a mix of tomato plum nectarine maybe something else..

Both grew white yeast or mold or something on the top surface of the fruit during the first stage of fermentation into alcohol. I just stirred it in when I stirred it on a daily basis.

After straining the fruit out, the white stuff is back as a layer on top. What is it? Should I try to get rid of it?

Couple pix below.....

Any help much appreciated!
IMG_20170826_083817591.jpg
white stuff on fruit
IMG_20170826_083817591.jpg (180.71 KiB) Viewed 310 times

IMG_20170830_090440720.jpg
white stuff a few days after I strained out fruit
IMG_20170830_090440720.jpg (202.67 KiB) Viewed 310 times
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Re: white yeast/mold/what on surface of vinegar

Postby bjdmytro on Sun Feb 25, 2018 1:48 pm

You should read up on kombucha fermentation and the SCOBY, because kombucha fermentation is a form of vinegar fermentation. The item of concern in your picture looks like a SCOBY, which is normal for vinegar fermentation and should not be stirred into the ferment. It is a protective layer that the microbes (bacterial & yeast). In time, it will form a thick rubbery pancake. I make apple cider vinegar every fall, seeding fresh pressed apple cider with some of last year's vinegar, and when the vinegar is done in December, there is about a 2" thick SCOBY on the top of the bucket.

Vinegar is a two fold fermentation process. Seeding a fresh sugary liquid with the starter, has the yeast anaerobically (meaning it doesn't need air) metabolizing the sugar into alcohol and CO2. Then the bacteria aerobically (meaning it needs O2 from the air) metabolizes the alcohol into acetic acid.
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Re: white yeast/mold/what on surface of vinegar

Postby bjdmytro on Sun Feb 25, 2018 1:49 pm

It is also hard to tell, but with some fruit ferments, I have gotten a white film to form that was not related to any of the microbes. Sometimes tartaric acid will take on the form of a white film on the surface.
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