The strength ceiling of household vinegar

Household vinegar is often described as if its strength were a matter of patience: leave wine exposed to air long enough and it will become as strong as the maker wishes. Stoichiometry sets a firmer limit. This paper calculates, from the oxidation of ethanol to acetic acid, the theoretical and practical acetic-acid concentration obtainable from starting liquids containing 5–12% alcohol by volume, after allowing for evaporation, over-oxidation, and incomplete conversion. At a combined retention of 0.8035, a 5% cider yields a practical vinegar of 4.13% acetic acid by weight per volume, and a 12% wine yields 9.92%, against a theoretical 12.34% for the wine. A starting liquid of at least 6.05% alcohol is required for a practical 5.00% vinegar. A surface-area-to-volume rule for acetification time is derived, in which time is inversely proportional to specific surface; under the stated calibration a 20-litre barrel requires 42.0 days, a wide tray 14.8 days, and a trickle system over packing 2.7 days. Finally, a pickling bound is derived for the dilution that occurs when vinegar meets the water held in vegetables. For 1 kg of vegetables covered with only 0.5 L of vinegar, the starting vinegar must be at least 6.75% to leave an equilibrated pickle at 2.5%; a nominal 5% vinegar leaves only 1.85% in that case, and does not satisfy the stated bound. All results are model calculations. SIMULATED, NOT MEASURED.