Botulism: A Deadly Concern

Botulism toxin is formed when the bacteria Clostridium botulinum is not properly controlled. This bacteria forms spores which act like survival pods allowing the bacteria to survive for many years in unfavorable environmental conditions. The conditions inside a jar of home canned food, however, are the perfect environment for the spores to emerge from their survival pod (germinate) and grow into the living form of the bacteria. During that growth process, a deadly toxin, or poison, is produced. When a person eats food containing the botulism toxin, the food will look and taste normal. Symptoms of botulism intoxication include muscle paralysis, blurred or double vision, confusion, and difficulty breathing. Urgent medical care is needed, and many patients require treatment in a hospital for weeks or months. Some survivors experience fatigue and shortness of breath for years. Luckily, with modern medical care, the survival rate has increased but the road to recovery is often long and difficult.

Control Botulism

The most effective measure to prevent botulism intoxication is to follow research-tested recipes when canning any food item. These recipes have been evaluated in a laboratory to measure critical factors such as pH (acidity) and heat penetration and have undergone microbiological testing to ensure that the recipe and process is safe. Safe sources of recipes include Penn State Extension's “Let's Preserve" series of handouts, the National Center for Home Food Preservation, the USDA Complete Guide to Home Canning and Preserving, and University of Georgia's So Easy to Preserve.

Research shows that spores of Clostridium botulinum cannot grow in high acid environments. Examples include fruit which is naturally high in acid and quick process pickles where acid (vinegar) is added to the product. Tomatoes are only mildly acidic. For this reason home canners must add additional acid in the form of bottled lemon juice, powdered citric acid, or vinegar to tomatoes and tomato products such as salsa. This is non-negotiable; there are no varieties of tomatoes to which acid must not be added.

Another way we can control the growth of Clostridium botulinum bacteria is by killing it with severe heat. Severe heat is defined as heat which is higher than the boiling point of water (212°F) – around 240°F. This is why a pressure canner is used to process low-acid foods; pressurized water boils at a higher temperature than water in a regular pot on the stove. Foods such as vegetables and meat, which are low in acid, must be pressure-canned for the appropriate amount of time to destroy Clostridium botulinum bacteria and its spores. When using a pressure canner, it is important to operate it correctly e.g., venting the canner, following the process time, and allowing it to cool naturally. More information about using a pressure canner correctly can be found in the canner's manual or in Penn State Extension’s handout, “Let's Preserve: Basics of Home Canning."

Use Research Tested Recipes

• When following a research-tested recipe, it is crucial that the ingredients be measured precisely and the recipe directions are followed exactly.
• Adding, omitting, or altering the amount of ingredients in a canned product can change the pH or the thickness which affects the heating characteristics of the food inside the jar.
• If a home canner wishes to add additional ingredients such as fresh herbs, pasta, or a thickener such as flour, they should be added at the time of serving, as to not compromise the safety of the product.

Following research-tested recipes exactly and using a canner correctly will ensure safe high-quality products that can be enjoyed by your family and friends.

If you have questions about a recipe or process, contact your local Penn State Extension office to get in contact with a Food Safety Educator.