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Cider Vinegar
Put half a pound of sugar into a half-gallon jar. Fill it with cider. Shake it well, and let it ferment for three or four months; the result will be two quarts of good, nicely-flavoured vinegar. Probable cost, 5d. per pint.
A two-line method that assumes you already know what cider is and what vinegar-making requires. Both assumptions need unpacking before this will work in a modern kitchen.
- "Cider" means alcoholic ciderIn a British book of this period cider is fermented apple juice, roughly 5-7% alcohol. Vinegar bacteria convert alcohol into acetic acid, so sweet supermarket apple juice or pasteurised non-alcoholic cider will not turn to vinegar; it will simply spoil. Use a hard cider, ideally unpasteurised and free of preservatives such as potassium sorbate, which is specifically designed to stop this fermentation.
- Air is the missing instructionThe one thing the recipe omits is the hinge of the whole process. Acetobacter is aerobic and needs continuous oxygen. Cover the jar with a cloth or coffee filter secured with a band, never a sealed lid, and fill it only two-thirds rather than to the brim so there is surface area for the bacteria to work.
- Do not shake it after the first day"Shake it well" applies only to dissolving the sugar at the start. Once a mother forms on the surface, agitation sinks it and stalls the conversion. Leave the jar undisturbed.
- Vessel sizeAn imperial half-gallon is about 2.3 litres, so a 3-litre jar gives the headspace you actually want. The stated yield of two quarts is a little under 2.3 litres, or roughly nine to ten cups.
- The sugar is optional and generousHalf a pound is about 225 g, which is a heavy dose for two quarts. It was presumably there to raise the alcohol of thin, weak farm cider before the vinegar stage. With a modern cider of ordinary strength you can leave it out entirely, or add no more than 50 g.
- Getting it startedA working cider cellar would have carried resident acetic bacteria; a modern kitchen may not. Add a few tablespoons of raw, unpasteurised vinegar with visible sediment, or a purchased vinegar mother, to seed the culture.
- Temperature and timeThree or four months is realistic at cellar temperature. At a steady 20-29C it will often be done in six to eight weeks. Taste from month one onward; it is finished when the sharpness stops increasing and no alcohol flavour remains.
- Strength, and what you may safely use it forHomemade vinegar is of unknown acidity. It is fine for dressings, sauces and deglazing, but should not be used for pickles intended for shelf storage or for any canning recipe, which requires a commercial vinegar of guaranteed 5% acetic acid. Strain, bottle and refrigerate to halt further change.
Vinegar is what happens to any alcohol left open to the air, and cider vinegar was for centuries simply the by-product of a barrel that had gone over. In the English cider counties -- Herefordshire, Somerset, Devon -- the surplus and the failures of the autumn pressing were routinely converted rather than thrown out, which is why a book like Cassell's, aimed at a middle-class household with an eye on economy, prints the method alongside the costing of fivepence a pint. The word itself comes through Old French vin aigre, sour wine, and the two-stage biology behind it -- yeast turning sugar into alcohol, then Acetobacter turning alcohol into acetic acid -- was only properly explained by Pasteur's work on fermentation in the 1860s, a decade or so before this dictionary appeared. The recipe's silence about air and about a mother suggests a writer describing a process everyone's grandmother had seen happen in a cellar, rather than one anybody had to be taught from scratch.