How is vinegar made?
Have you ever tasted wine that has soured after being opened? That’s vinegar! In fact, vinegar derives its modern name from the Old French, vinaigre, which means “sour wine.”
Vinegar is a sour-tasting liquid comprised mainly of acetic acid and water. Acetic acid, which gives vinegar its pungent smell and flavor, is produced by the fermentation of ethanol by acetic acid bacteria. Vinegar is approximately 3% to 9% acetic acid by volume.
Once oxygen comes into contact with wine, a process called oxidation begins. When the acetobacter (acetic acid bacteria) found in wine is exposed to oxygen, it turns alcohol into acetic acid. As a result, the wine “sours” because it has been converted into acetic acid.
Vinegar can be made from any alcohol-containing liquid, including wine, beer and fermented fruit juices and nectars, or, any other liquids containing sugar (which naturally ferments).
How is vinegar made?
There are two main processes by which vinegar is made: the fast and the slow process.
In the fast process, vinegar can be produced in as little as 20 hours to 3 days.
In the slow process, which is how vinegar is traditionally made, fermentation takes several months to a year.
Both processes require the presence of a non-toxic slime called “mother of vinegar,” which is made of acetic acid bacteria and cellulose.
In the slow process, sometimes called the Orleans Process, mother of vinegar naturally accumulates over time as the chosen liquid ferments in wooden barrels. Holes are drilled at the ends of the barrels a few inches above the surface of the liquid and left open, but covered with a fine screen to prevent contamination. Next, fresh vinegar making up 20% to 25% of the volume of the barrel is added in order to acidify the liquid and promote growth of acetic bacteria. As the newly added vinegar bacteria mixes with the liquid, and oxygen enters through the screened holes in the barrel, a thick slime of mother of vinegar develops. The mixture is fermented for several months, and the gelatinous slime removed before the vinegar is finally bottled.
The fast process of vinegar production is similar to the slow process, except that machines are used to promote oxygenation to speed up the fermentation process, allowing vinegar to be produced in a matter of days or even hours.