Until recently, cider and distilled vinegar sold in the United States was dependably diluted to 5-percent acetic acid. All U.S. Department of Agriculture home-canning recipes that call for vinegar specify a strength of 5 percent, and in writing recipes myself I’ve assumed that cider or distilled vinegar will have this strength. When I’ve called for wine vinegar, I’ve assumed a strength of at least 5 percent, since wine vinegars on the market sometimes range in strength as high as 7 percent. Only when I’ve specified rice vinegar have I allowed for less acidity, because rice vinegars are typically sold at 4 to 4.3 percent acid.
At a class I recently taught at the Culinary Center in Lincoln City, a student told me she’d bought a bottle of Four Monks cider vinegar labeled as 4 percent acid. I was perplexed, especially because Four Monks is one of the country’s leading producers of vinegar for home canning, if not the leading producer. And then another student pointed out that the wine vinegar we’d just used for pickling plums was also labeled, by a company I’d never heard of, as 4 percent acid.
At home a few days later, I checked the Food and Drug Administration’s “standard of identity” for vinegar. This regulation requires a minimum acidity of only 4 percent, for vinegar of any sort. So Mizkan, the Japanese company that owns Four Monks, and other 4-percent producers are staying within the law, while hoping consumers won’t notice the change. Or maybe they’re hoping we’ll die quietly?
Actually, if you’ve accidentally pickled with 4-percent vinegar, your family is highly unlikely to die of botulism. USDA pickle recipes, and most of my own, produce pickles far lower in pH (and therefore higher in acid) than the 4.6 percent that’s considered the safe limit for avoiding botulism. If you’re worried, you can buy yourself a pH meter and check your pickles, after the jars have sat on the shelf for several weeks (grind up a jarful in a blender, add distilled water if the slurry is very thick, and calibrate your pH meter before taking the measurement).
If you’re using old family recipes, though, your pickles canned with 4-percent vinegar may possibly be dangerously low in acid. At the very least, you probably didn’t get what you thought you’d paid for.
If you have 4-percent vinegar sitting on your shelf right now, you can still use it for pickling if you follow the formula I published earlier this year for rice vinegar.
The next time you go shopping for vinegar, be sure to read the label carefully. Look for the percentage of acid, and while you’re at it make sure you don’t buy “apple cider flavored vinegar”—distilled vinegar with flavor chemicals added—in place of true cider vinegar. That ugly bit of marketing trickery has been going on for about fifteen years now.