The discovery of the winemaking process apparently coin­cided with that of the vinegar-making process, which is hardly surprising.

One of the most important steps in wine­making is limiting exposure of the develop­ing wine to air. Although air is essential to the process while yeast molecules ferment the sugar in grapes, after this step (called alcoho­lic fermentation), exposure to air must be controlled, to prevent the fermented juice from turning sour through the development of acetic acid. Microbes in the air metabolise alcohol in the fermented juice, leaving behind just the acids and producing what the French named vin aigre, or “sour wine”.

Vinegar is a natural preservative. There are records of the Babylonians making it as early as 4000BC, using wine made from dates or raisins that they flavoured with herbs and spices. They used vinegar to pickle vegetables and flavour meat.

The Romans made a drink called poscafrom vinegar and water. In the Roman cookbook Apicius, a version of posca with added honey is recommended. And, if you are a regular reader of this column, you might recognise that a more modern version of this is shrubs, a sweetened vinegar syrup mixed with water or soda, which is refresh­ing on its own or used as a base for cocktails.

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Until the 17th century, making vinegar was a lengthy process. Partially filled con­tainers of wine or other alcoholic drinks of inferior quality were left open, exposing the contents to air and turning the liquid sour.

The first innovation in vinegar-making was developed by the French, the vinegar-to-be periodically poured over grapevine twigs to increase aeration. In the 18th century, a Dutch scientist came up with the idea of continuously trickling wine to speed up the process. Then came Louis Pasteur, who discovered which microbes worked best to make vinegar – they were dubbed Acetobacter pasteurianus (after the man himself), Acetobacter aceti and Gluconobacter.

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What’s known as the Orleans process was developed to speed things up, with partially filled barrels of wine being inocu­lated with the “mother” from a previous batch of wine that has already been turned into vinegar. This shortens the process to about two months.

What exactly is the mother made of and what does it look like? In natural, unpasteur­ised vinegar, it floats and is slightly cloudy. A good mother is a semi-coagulated mass (think of a jellyfish) that sits either at the surface (active) or on the bottom (not so active). It is the purest form of acetic acid and cellulose bacteria (a good bacteria; not the sort that will make you sick).

In commercial vinegar, it is filtered out so that the liquid is clear, but behind the scenes, it is used to start another batch.

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Those who have leftover wine can try making their own wine vinegars. In addition to leftover wine, you need an impeccably clean wide glass container (sterilise it with boiling water), a clean cloth (no fabric softener) and some mother from a natural vinegar. I use unfiltered apple cider vinegar, such as Braggs. Assuming that you have about 500ml of leftover wine, add 50ml of the mother, cover the jar with the clean cloth (tie string around the jar) and leave it in a warm place. If you like, add flavouring agents such as peppercorns and dried botanicals (bay leaf, etc) but don’t use anything fresh as it will make your vinegar go off. In two or three months, you will have your own bespoke vinegar. As you use up the vinegar, you can periodically add more wine to the container, making sure you don’t add too much at one time.

Nellie Ming Lee is a food stylist and part-time sommelier studying with the Court of Master Sommeliers