This story was originally published in July 2023.
As cucumbers are beginning to ripen around Maine, home canners are beginning to put up foods for the cold months. But food safety experts are warning them to check vinegar labels first.
Although many vinegars still clock in at 5 percent acidity or above — which is safe for canning — experts warn that a small but growing number of vinegars of lower acidity are becoming available and shouldn’t be used. They won’t preserve food safely.
“The issue now is the vinegar products you can find have different acidity levels,” said Kathy Savoie, University of Maine Cooperative Extension professor. “You cannot substitute any of those for 5 percent acidity.”
In 2023 the National Center for Home Food Preservation issued a statement recognizing an increasing concern and questions among home canners specifically about vinegar with four percent acidity level. All United States Department of Agriculture and the National Center for Home Food Preservation approved canning recipes for picking use vinegar with a 5 percent acidity level.
“It is strongly advised against using vinegar with lower acidity levels [less than 5 percent] as it may not be sufficiently strong enough to ensure the safety of the canned products,” according to the statement.
Although the white distilled and apple cider vinegars most commonly used for pickling are not easily found in greater Bangor with a lower than 5 percent acidity level, consumers should still use caution.
“People need to be careful where they source their vinegar,” Savoie said. “Read the label and make sure you find the one that says 5 percent.”
Some brands have the acidity level prominently noted on their labels while others include it in much smaller print with the list of ingredients. Some, however, don’t list the acidity at all. It’s best to avoid those for canning.
Vinegars with acidity of less than 5 percent won’t kill the dangerous bacteria that causes botulism, a potentially fatal disease. And though vinegars with higher acidity levels are available as well, they aren’t necessarily what you want for pickling either.
“There are some of the wine vinegars that get up to 6 percent acidity,” she said. “But those have not been food safety tested.”
If you happen to process pickles with the wrong vinegar — one with too low acidity — it’s not a total loss though, if you act quickly.
“If they were processed within 24 hours, you can refrigerate them for up to a month and they will be safe,” Savoie said. “If it’s been more than 24 hours since you processed them, dispose of them.”
