Botulism and Home Canning

Q:  With the cost of food going up, I thought that I would start canning foods from my garden. Everything I read about, though, talks about being careful to prevent botulism. This seems pretty scary.

What is botulism and what can I do to prevent it?

A:  Botulism is deadly - I guess that is pretty scary.

Botulism is caused by a toxin that is produced by a bacterium called clostridium botulinum. It forms in foods that are improperly stored, especially canned foods.

Symptoms of botulinum toxicity include gastrointestinal upset and weakness starting at the face and moving down the body into the chest.

It causes difficulty with breathing by affecting the muscles required to breathe, which is why the infection can be deadly. Symptoms usually start around 12 hours to 2 days after ingestion of the botulinum toxin.

Having said all of that, I would still encourage you to try canning. I am certainly no expert in canning or preventing botulism while canning. For that, I had to ask Grandma Sally and Grandma Cyrilla - combined they have over 120 years of canning experience without any deaths or illness attributed to their canning. They both stated it was very important to ensure proper seal formation on the jars.

The heating process during canning some foods helps to prevent infection from bacteria. Using a pressure canning device helps to ensure that the food and jar have been heated to a high enough temperature to kill the spores that produce the botulinum toxin.

Prior to eating, though, the jars and food should again be boiled as this will cause break down of the toxin if present.

The brine in many canning recipes contains salt or is acidic, which also helps to inhibit some bacteria growth. Before eating canned foods, be sure that the jar seal is still intact, and that the food has normal color, smell, and appearance.

Some forms of botulinum toxin do not alter the foods characteristics, so it is still best to prepare the foods properly rather than rely on the smell or appearance to ensure the food's safety.

Botulism is incredibly rare - only around 100-150 cases of botulism occur every year - so I would encourage you to start your new hobby using some minor precautions.

Deidre L. Faust, MD, is a Staff Physician (Internal Medicine) at the Medical College of Wisconsin's Plank Road Clinic. Her column appears in the Milwaukee Journal-Sentinel.