1/4cup of apple cider vinegar with a mother (see notes)
Mix the wine and the vinegar mother in a glass jar. I don’t recommend using plastic or metal because they may react to the acidity in the vinegar. Shake the vinegar bottle before measuring to ensure that the vinegar is well mixed.
Cover the jar with a cloth or coffee filter held in place with a rubber band or jar ring.
Place the jar somewhere dark and at room temperature to ferment. I usually stash all my vinegar in a closet.
Leave the wine to ferment for 2 months.
At some point, the wine may smell bad, like nail polish remover. That is part of the process as ethanol is converted to acetaldehyde before turning into acetic acid.
The vinegar is ready when it is sour. You can either use a kit to test the pH or taste it. If it’s sour then it’s ready to be bottled.
Store finished vinegar in an air-tight bottle. I recommend letting it age for another month or two. While it won’t become more acidic, aging will help to develop the flavor.
Homemade vinegar will last for years in a dark location. The flavor will likely continue to improve as it ages. (True balsamic vinegar is aged for over 12 years!)
Wine may naturally ferment into vinegar, but adding a bit of acetic acid bacteria is definitely recommended.
Make sure that the apple cider vinegar contains a mother. Look for brands labeled raw, unpasteurized, or with mother.
Often a thick rubbery disk will form on top of the vinegar. It’s called a vinegar pellicle, and it is perfect for culturing future batches of vinegar. Save it and use it instead of the ACV.
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