Canning is an effective way to preserve foods, but officials with the University of Missouri Extension say it requires care to prevent foodborne illness, particularly botulism.
A primary consideration is acidity, points out food processing specialist Laksmikantha Channaiah with the state extension office. Food products with a pH of 4.6 or lower are classified as high-acid and can be safely processed in a boiling water bath. Acidification using vinegar, lemon juice or citric acid is often necessary, especially in recipes like salsa, where ingredients vary in natural acidity.
Channaiah outlined several other important considerations to ensure home-canned foods remain safe for consumption.
The processing method and time are critical, he said. Always follow tested recipes from trusted sources such as the U.S. Department of Agriculture or the National Center for Home Food Preservation. These guidelines specify the correct processing times and temperatures needed to eliminate pathogens.
Water boils at lower temperatures as elevation increases, so it’s important to make adjustments for altitude, Channaiah noted.
Always use fresh, high-quality produce, and wash thoroughly to reduce cross-contamination. Follow recommended cutting sizes and proportions, as altering these can affect heat penetration and overall safety.
Channaiah emphasized the importance of using clean, undamaged jars and new lids to ensure a proper seal. Maintaining the correct headspace allows for proper expansion during processing. After processing, jars should form a vacuum seal, indicated by a concave lid that does not flex when pressed.
Finally, storage and inspection are key steps, according to extension officials. Home canners should store jars in a cool, dark and dry place, labeled with the date. Before use, check for signs of spoilage such as bulging lids, leaks, cloudiness or off odors. If any of these are present, discard the food without tasting.
For more information, the MU Extension publication “Safe Home Canning Basics” is available for free download at muext.us/FoodPreservation.
