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I did a little bit of a fermentation experiment by adding water to a large jar half full of fruit (nectarines). I did not add any sugar or yeast. The final product is very sour, which I'm assuming is acetic acid but I'm quite sure there is some ethanol in there as well. My 'burping' process may have added too much oxygen which is why I'm assuming vinegar.

Seeing as ethanol has an SG of <1.00 and acetic acid has an SG of >1.00, a hydrometer reading will not be an accurate way to measure the alcohol content - I also did not take an initial reading of the 'mash/wort' (sorry, I'm usually a beer guy).

Are there methods I can use to measure both acid content and ethanol content?

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Acid content is generally measured by titration - a pH meter or test papers do not measure content only "acidity".

The sourness is IMHO likely to be lactic acid as lactobacillius are generally present on fruit and will work directly on the sugars present. Acetobacter need alcohol (and oxygen) to produce the acetic acid (vinegar) so will generally only work in later stages of fermentation.

If the drink is a little sour it is sometimes possible to reduce the acidity with calcium carbonate (best) or sodium bicarbonate (second best). This does not work usefully with VERY sour solutions and be aware it may foam for a while.

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