Botulism and Canning Safely

When I mention this blog, it rarely takes noncanners long to reveal they are afraid of making their family sick and to ask for the secret to canning safely. Their fear is of the big, scary B word: botulism. But what strikes me is their belief that they need to be let in on a secret to avoid it.

Honestly, there is no secret to safe canning. Everything you need to know is in every decent book and on every decent website that covers the topic. Canning is a process, but it’s not a mysterious one: If you can follow directions, you can get it right. Or, in the words of Kevin West, author of the fabulously informative Saving the Season, “If you can safely prepare chicken, a potential vector for food-borne pathogens such as salmonella, then you can handle home canning.”

Unfortunately, botulism has become a boogeyman, the arch villain of a cautionary tale who peers over the rim of a boiling water bath at many home canners. It doesn’t have to be that way.
Botulism has become a boogeyman who peers over the rim of a boiling water bath at many home canners. But there is no secret to safe canning. Read more about botulism and canning safely.

What Is Botulism?

The first step to overcoming a fear is to understand it. So let’s get somewhat scientific for a moment. According to the U.S. Department of Agriculture, Clostridium botulinum is a bacterium that is “found everywhere” and “generally harmless.” But when its spores grow and reproduce, they release a toxin that causes botulism. This illness can be deadly if not treated immediately. And the ideal environment for the bacteria’s growth is a jar of improperly processed food.

It sounds scary, right? The thing is, botulism is easy to avoid and extremely rare. The Centers for Disease Control and Prevention estimates that 1 in 5 people can food at home, yet its latest, 2014 report confirms only 15 cases of foodborne botulism. In comparison, the U.S. Food and Drug Administration reports an annual estimate of 48 million cases of foodborne illness in the country—or 1 in 6 people—from E. coli, Salmonella, and other cooties, few of which come from homegrown, home-canned foods. So botulism shouldn’t keep you from canning; it should simply remind you to do so safely.

How Do I Can Safely?

The opening paragraph of the USDA’s Complete Guide to Home Canning, 2015 revision, begins, “Caution: All home-canned foods should be canned according to the procedures in this Guide. Low-acid and tomato foods not canned according to the recommendations in this publication or according to other USDA-endorsed recommendations present a risk of botulism.” With all due respect to government public health officials, this sounds to me like the opening lines of 196 pages of fine-print legalese rather than encouragement and support to people about to process their first jars of homegrown raspberries. But read those sentences more closely, and the dementor becomes a boggart. All you need to finish it off is acid or heat. Here’s why.
Botulism has become a boogeyman who peers over the rim of a boiling water bath at many home canners. But there is no secret to safe canning. Read more about botulism and canning safely.

  1. Bacteria do not grow in high-acid foods. The acid kills them all—including the bacteria that cause botulism. High-acid foods have a pH of no more than 4.6. And guess what? Almost all fruits are naturally below that pH level. So you can’t get botulism by canning at home, in a boiling water bath, a jar of Apricot–Raspberry–Mint Jam, applesauce, or plum preserves. The U.S. Food and Drug Administration backs this up with a list of the pH for almost anything you may want to can at home. Simply scroll down to find the item you want to process. If it has a 4.6 pH or lower, you’re good to go.
  2. But what about those items on the FDA’s list above a 4.6 pH? You can still can them and never risk botulism, and you have two options for doing so.

  3. Again, acidity kills bacteria. So adding acid erases the fear of botulism for any food naturally low in acid. Low-acid foods are mostly vegetables, fish, and meat. The trick to canning these in a simple water bath is to figure out how much acid to add to lower the pH to the safe zone. Some foods, like tomatoes, are on the cusp, so it takes just a tablespoon or two of lemon juice or vinegar to ensure you’ve killed the nasties. Others, such as snap beans, need to be pickled in a large amount of vinegar before they go into the water-bath canner. This is why tested recipes are useful, but the math isn’t that hard: Canning guru Linda Ziedrich points out that a 1:1 ratio of 5% acidity vinegar to water ensures you can pickle just about anything. So savor that sharp bite of Dilly Beans—you’ll never get botulism from them.
  4. But what if you don’t like the zing of pickled beans, or if you are rich in salmon, potatoes, or anything else you can’t imagine as a pickle? This leads to your other option for low-acid foods.

  5. Extreme heat kills bacteria. Even hardy C. botulinum spores can’t survive temperatures above 240°F. In other words, they are destroyed by pressure canning. So if pickled vegetables and meats aren’t appealing, it may be worth forking out for a pressure canner. Get one that is certified by Underwriters Laboratories, which tests and approves this tool; look for one that has the UL safety symbol. Small pressure cookers that may be handy for a fresh meal with dried beans or a thick cut of meat won’t hold a full round of jars or hit the temperature required for long-term storage.
  6. Once you’ve decided to kill off bacteria with acid or heat, it’s simply a matter of following the steps that seal your jars. Think of it like learning to drive a car: The process may be a little jerky at first, but the more you do it, the smoother it gets. Which brings us to one final rule of safe canning.

  7. When in doubt, throw it out. Just as with a car, your canning process won’t start, move forward, and stop safely if you just wing it or become distracted and miss a key step. If you lose count while measuring vinegar, forget to set your timer, or fear you’ve made any other mistake along the way, it’s okay to chalk it up to experience, toss that batch, and begin again. Letting a finished jar that you’re afraid to open sit on your shelf for 2 years won’t make you more confident in that particular jar or the next one you want to can. Canning safely isn’t just about avoiding botulism; it’s about preserving good food you’ve taken time to grow or acquire and gaining the confidence to continue to do so.

If you’re still worried that you could make your family sick, consider this (again from Saving the Season’s Kevin West): “Often more than one preserving agent is at play…. When we make marmalade at home, we start with citrus (which has natural acidity), then add sugar and concentrate it by boiling (lowering water activity). Next we ladle the hot product into a Mason jar (hermetically sealed container) and process it in a boiling-water bath (thermal processing).” In that description alone, I count four ways in which not just C. botulinum but any other food spoilers are defeated. You can’t get much safer than that.


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