White Wine Vinegar

White wine vinegar has never enjoyed the cachet of its red-hued brethren—at least in this country. American cooks tend to relegate it to backstage tasks: quietly punching up pickle brine, brightening butter-based sauces, providing unobtrusive (and untinted) foundation for delicate citrus vinaigrettes.

Of course, that's when we use it at all: According to the Vinegar Institute, an industry trade group, Americans buy a much higher percentage of distilled white vinegar (46 percent) than any other variety, including cider vinegar (22 percent), red wine vinegar (12 percent), balsamic (10 percent), and rice vinegar (5 percent). White wine vinegar? Lumped together with malt vinegar and obscure fruit vinegar it is in a category comprising just 5 percent of total sales.

Does brand even matter? To find out, we purchased 7 national supermarket white wine vinegars, which tasters sampled straight (sucking the liquid through sugar cubes, a trick experts use to minimize palate fatigue); whisked into a simple vinaigrette (with mild canola oil); and reduced in a beurre blanc. They also tasted 7 batches of pickled green beans, jarred for a month to give our acidic contenders time to work their magic.

Fermented Wisdom

After weeks of diligent puckering, one thing was clear: The vinegars differed dramatically. Some were quite aggressive in taste; some boasted floral or fruity notes; others had fermented, malty qualities. The notion of white wine vinegar as a brandless, faceless commodity was duly put to rest.

Less clear was how to interpret the testing data. There seemed to be no discernible pattern, as the winning vinegars from one tasting ended up in the lower ranks of the next one. To figure it out, we first needed a better grasp on the basics of vinegar making.

All vinegar is the product of double fermentation. In the first round, yeast transforms a sugary or starchy substance (apples, grains, grapes) into alcohol (cider, malt, wine). In the second, the bacteria Acetobacter aceti transform the alcohol into acetic acid, and vinegar (cider vinegar, malt vinegar, wine vinegar) is born. Nowadays, yeast and Acetobacterare strategically introduced, but once upon a time the organisms arrived naturally from the air. After the second fermentation, the liquid's acidity level has reached 10 to 12 percent, a bit too harsh for consumption. So the vinegar is diluted with water almost by half. European wine vinegars are legally obligated to have 6 percent acidity or higher; in the United States, the minimum is just 4 percent.

White wine vinegar manufacturers today generally handle only the second fermentation first-hand, purchasing pre-made "wine stock" (wine blends of slightly lesser quality than drinking wine) from local vineyards. Which varietals? All kinds. Manufacturers maintain flavor-profile consistency from batch to batch by adjusting the proportions of wine stock of differing characters, just the way a winemaker would. Some stocks may be chosen for color, some for fruitiness, others for depth.

Clue Sniffing

Back to the results, we first zeroed in on acid levels, which ranged from 5 percent to 7.5 percent. Any hopes that such an obvious clue would bring order to the proceedings were quickly dashed: In every test, the high-acid and low-acid brands were evenly distributed from the top of the ranks to the bottom. Likewise, attempts to divine a pattern based on national origin proved a dead end.

It wasn't until we took a closer look at tasters' comments that we found our first important clue. In the plain tasting, the losing vinegars were indicted consistently for artificial fruit flavors and harsh, chemical off-notes. Especially interesting were the repeated references to "nail-polish remover." (Ethyl acetate, the solvent that gives nail-polish remover its characteristic smell, is often used in confectionery to manufacture artificial fruit flavors.)

Were some manufacturers adding ethyl acetate to their vinegars to ramp up the fruity notes? Not quite. A white wine vinegar's flavor profile can be adjusted through wine-stock blending alone, but vinegar makers have another trick up their sleeves: adjusting fermentation times. If you stop fermentation before all the alcohol gets converted to acetic acid, you end up with a more pungent solvent-y flavor. Why? The excess alcohol reacts with the newly formed acetic acid to create a new compound: ethyl acetate. Vinegar makers weren't adding it to their brews; they were letting it occur naturally.

The Raw and the Cooked

For further analysis, we poured the samples into vials and sent them off to a Boston-area laboratory. A week later, the results came back. Sure enough, ethyl acetate levels varied markedly -- from trace amounts (less than 10 milligrams per liter) to a whopping 713 milligrams per liter!

Suddenly, the pieces were falling into place. The vinegars with the highest concentrations of ethyl acetate made up the lower ranks of the plain and vinaigrette tastings. Tasters liked the bright, fruity notes of these samples but decried their artificial off-tastes. The top-ranked vinegars in these two rounds had low concentrations of ethyl acetate and were generally described as fermented, "malty," and rich.

For the cooked applications, the results were almost the reverse: The vinegars with more ethyl acetate carried the day in the pickle and beurre blanc tasting. And it didn't take much research to figure out why. Both recipes call for bringing the vinegar to a boil--at which point ethyl acetate would evaporate, leaving behind only the bright, clean notes that tasters liked in these vinegars. By contrast, the malty, fermented, darker notes of the vinegars with less ethyl acetate--which had proved such an advantage in the uncooked tests--lacked the brightness to cut the richness of the beurre blanc or to complement the pickle brine.

Given the fact that most Americans don't keep even one brand of white wine vinegar in the pantry, a bipartite recommendation may be overkill. We did find a well-made brand that contains only a trace amount of ethyl acetate but still has enough fruity brightness to stand up convincingly to even the most buttery beurre blanc.