This is a reprint of a file I wrote for the group Vinegar Makers on Facebook. Come join us if dropping acid is your thing!
While pH is one measure of how acidic your vinegar is, there is another value that can tell you if your vinegar is safe to use for home canning. If you intend to use homemade vinegar for canning purposes, you need to know how strong your vinegar is, by measuring its total acidity. This requires a readily available kit called an acid titration kit, but because those are borrowed from the wine making industry, some special math is needed to make their results appropriate for our much-higher-acid vinegars. Vinegars with an acidity of 5% or higher are considered safe to make a canned product shelf stable.
This text is borrowed from Harry Rosenblum’s Vinegar Revival:
To test for acid content, you will need an acid titration kit like the ones sold for wine making; they cost about $20. You will need to adjust your method, as the instructions contained will be for testing a much smaller percentage of acid in wine (usually 0.3 to 0.7 percent). Your titration kit should include the following:
- 20-milliliter syringe
- 150-milliliter testing cup
- 15-milliliter dropper bottle of indicator solution
- 100 milliliters of base liquid
Follow these instructions for testing the acid level in your vinegar:
- Use the syringe to place 2 milliliters of vinegar in the testing cup. Add 20 milliliters of water and 3 drops of the indicator solution, and stir to combine.
- Fill the syringe with 10 milliliters of the base liquid. Add the base, 1 milliliter at a time, until the liquid turns pink. Once the liquid has turned pink, note how much of the base you added to get the reaction (for example, if you have 4 milliliters left in the syringe, then you used 6 milliliters of base).
- Multiply the number of milliliters of base you added by 0.6; the result is the percentage of acid in your vinegar. So in this example, you would multiply 6 by 0.6 to get 3.6, or 3.6 percent acetic acid, which would taste tart like vinegar and be great for drinking or cooking with, but not acidic enough for canning.