Perfect for embalming a sprig of thyme, embracing a pool of extra virgin olive oil, but equally adept at removing even the toughest soap scum, vinegar is one of the most versatile—and one of the oldest—condiments. It delivers a sharp, bracing bite to the tongue and a heady, pungent aroma to the nose.
The same process that ruins wine (in French 'vin aigre' literally means 'sour wine') creates the prized sourness of vinegar. There's a long explanation about how, but in short, there's a family of acetobacter microbes that make their living by consuming alcohol (in the presence of air) and excreting acetic acid.
While this conversion process is a very bad thing for wine, and why so many of those gray rubber stoppers and white vacuum pumps make it to the kitchen tool drawer—it's a very good thing for salads. But acetic acid alone isn't enough to make vinegar delicious. Wonderful vinegars mainly come from wonderful pre-cursor products that have their own flavor profile, and that have been soured in a careful, controlled way, and then stopped just at the right point.
Balsamic, Cider, and White
The character of true balsamic vinegar from Modena, Italy, for example, starts with the boiled down, concentrated juice of Trebbiano, Lambrusco and other grape varieties, providing the sugar for fermentation. After inoculating the concentrate with a microbial stew by the maker, it takes years and years (we're talking up to 25) of additional fermentation in a progression of ever-smaller, wooden barrels of various kinds, each contributing unique character and flavor. The wood for these barrels can be exotic, and the progression is a highly guarded trade secret by the maker.
Apple cider vinegar, the current cash cow of predatory diet 'aid' shysters, benefits from the natural complexity of apples, one of whose components is malic acid. So what, you say? Malic acid is the fuel for another process called malolactic fermentation. This particularly yummy sort of 'going bad' changes the malic acid into milder lactic acid as well as producing, as a by product, the same chemical that's butters up the flavor of chardonnay, margarine, and 'I Can't Believe It's Not Butter'. Good apple cider vinegar, like balsamic, ages slowly, giving the vinegar time to undergo a whole series of reactions, including malolactic fermentation, that enrich and complexify the final product.
On the other end of the spectrum, white vinegar is literally just acetic acid and water. Some large commercial labs create acetic acid from, of all things, propane! Yes, the fuel you use to cook your chicken on in the back yard. While others ferment it from pure alcohol (who knows how they make that!...and while I'm in a parenthesis...note to self: Don't spend any money on 'organic' or 'brand name' white vinegar—it truly matters not!)
Chinese black vinegars made from toasted rice, millet and other grains can have as little as two percent of acetic acid, while red wine vinegars can have as much as seven percent or eight percent or even more. Most vinegars will tell you on the label, but as you can easily see, when you're buying vinegar, you're buying lots of other liquid: some of it delicious, some of it utterly without character.
What About Safeway?
In between the lush, teaming, complex true balsamic from Modena and the barren, stark and harsh white vinegar of Heinz, there lurks a shelf-load of concocted vinegars with leaves, sticks, fruit, coloring, and host of other gimmicks. Unless you explicitly buy vinegar made from apple cider, for example, you're likely just getting some acetic acid, caramel coloring, and maybe a few other additives--you can be sure, there's no malolactic fermentation happening there. So beware of what you buy. If you'll be eating the vinegar on a salad, check the label and weigh how much love went into the process. If no aging has taken place, for example, it's likely the vinegar lacks complexity which can be perfect for cooking, but maybe not naked from the bottle to adorn bread.