It’s the Big Evil in canning. Botulism causes paralysis, death, and long-term rehabilitation for survivors. But understanding how botulism forms, and how to prevent it, keeps you safe.

Erica Strauss, of the blog Northwest Edible Life, stood in front of a Seattle audience to promote her new book release. Someone asked a question about canning. To get a demographic of her audience, Erica asked who had canned. Three-quarters of the group admitted they wanted to but hadn’t tried it.

“Is it because you’re afraid you might kill your family with strawberry jam?” Erica asked.

They all answered yes.

A desire to demystify botulism for home canners led Erica to write a blog post: “How Not to Die from Botulism: What Home Canners Need to Know About the World’s Most Deadly Toxin.” Here, she lays it all out: Botulism causes, the life cycle from spore to bacteria, and how to avoid the toxin altogether.

“The fear factor doesn’t do people any favors,” Erica explains. “When it comes to botulism and home canning, knowledge is power. If you understand exactly what the risk factor is and how the risk factor develops, then you can take steps to eliminate that risk. And it’s not hard to do this. For the most part, canners just have to follow safe processing time and safe processing pressure.”

Erica is one of many home canners that preaches the solid wisdom of acidity, processing times, and following strict rules. The USDA and the National Center for Home Food Preservation offer free, up-to-date information. Access this online or purchase the most current Ball canning book version, keeping in mind that scientists keep learning about botulism causes and prevention. Always follow the newest, accredited guidelines. Blogs can be great sources of information but, when it comes to deadly toxins, be wary of those that don’t demand solid safety guidelines.

Botulism comes from three bacteria: Clostridium butyricum, C. baratii, and most commonly C. botulinum. It’s the C. botulinum that causes problems for home canners. Unlike many bacteria, botulism has a unique life cycle. And it’s only deadly at a certain stage.

Botulism Spores

Round and hard-shelled, spores are the dormant form of C. botulinum. They survive freezing, boiling, bleach, and acidity. Botulism spores exist virtually everywhere: In moist soil, the dust on your shelf, animal intestinal tracts, and the delicious product of honey bee farming. It’s theorized they can even remain viable for thousands of years. The only proven method of destroying them is raising temperatures above 240 degrees Fahrenheit until all spores die. This is only attainable, at home, with a pressure canner.

Erica Strauss says there are no shortcuts for processing time. If USDA guidelines specify 75 minutes for meat, shortcuts may result in undestroyed spores.

But the spores, themselves, are not harmful. Eating them cannot hurt you … unless you are an infant. To learn why children under one year should never eat honey, read the second segment on botulism symptoms.

Because spores are so prevalent, home canners should always assume they are present and will grow if conditions are right.

Botulism Bacteria

Before they can become active bacteria, which grow and create the toxin, spores must have three specific requirements.

• An anaerobic (oxygen-free) environment.
• A pH above 4.6.
• Temperatures between 37 degrees and boiling.

All three requirements are met with low-acid canning. Processing removes oxygen. Mason jars then sit at room temperature, which bacteria love. If contents aren’t acidic enough, spores become bacteria and botulism causes the toxin to be made.

Microbes create byproducts as they reproduce: some beneficial and some detrimental. Yeast’s byproduct is alcohol; lactobacillus’ byproduct is lactic acid. C. botulinum creates botulism toxin.

Even if conditions become unfavorable and bacteria revert to spore form, the toxin remains.

Botulism Toxin

This powerful neurotoxin disrupts the signals telling muscles what to do. It’s said that a pint of pure botulism toxin can kill every human being in the world. Deaths also occur from botulism in chickens, pets, and other animals.

Because most bacteria can’t exist over 160 degrees, and all bacteria die at 212 degrees, some canning blogs suggest boiling suspect foods after breaking the seal. The toxin can be neutralized by boiling for at least 10 minutes, as long as every possible contaminated part reaches high-enough temperatures, but professionals in the food industry learn not to even risk it. Certified Sous Chef Tamalyn Karp says, “In the culinary world, we are taught that once C. botulinum has produced the toxin, you cannot rid the food of the toxin. Not without turning your food into inedible mush/charcoal.”

Sean Sullivan, a chef with a Bachelor of Science in chemistry and a specific interest in food preservation methods, confirms, “Same reason we throw out bulging cans.”

If botulism contamination is possible, home canners should discard suspect jars. Buy new ones; don’t risk it.

Can you introduce contaminated food to high acidity and kill the toxin? Sean says, “You needed the vinegar or sugar before.”

Tamalyn confirms, “The toxin cannot come out of dormancy if the acidity is high enough. However, once the bacteria have begun producing the toxin, the amount needed to seriously harm or kill a human is not very high.”

Even with the frightening reality of botulism causes and toxicity, it’s easy to avoid. High acidity foods such as pickles, jams, and most fruits, are safe. Pineapple, figs, and tomatoes can have varying acidity, so adding lemon juice creates that 4.6 pH threshold. And, if you don’t want acidic marinara, freeze it instead. Freeze or dry any low-acid foods you don’t want to pressure-can. Simply avoiding those ideal conditions keeps spores from activating.

If you do home canning, have you explored botulism causes and how to stay safe?