balsamic vinegar in/on olive oil
My raving over how much I liked both the oil and vinegar earned me more bottles this past Christmas:
Oil - roasted garlic, basil, sun-dried tomato
Vinegar - black current, honey balsamic, raspberry
(1) Vinegar can be made from any fruit, or any material that contains sugar.
(2)Two processes are involved: (a)alcoholic fermentation which happens when yeasts change natural sugars to alcohol (controlled conditions required) - and (b) the conversion of the alcohol portion to acid, specifically acetic acid.
Apart from water, this acid is the primary constituent of vinegar, yet acetic acid is not vinegar. Vinegar has a lot of vitamins and other compounds not found in acetic acid like Vitamin B-1, riboflavin and mineral salts that all give
vinegar its distinct flavor.
Those two biological processes that turn sugar into acetic acid have to be carefully controlled. You're dealing with bacteria here, the ones that convert the alcohol portion to acid which ferments and forms the vinegar. Controlling how and for how long this happens is super important and should be carefully monitored.