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COLUMBIA, Mo. – Canning is an effective way to preserve foods, but it requires care to prevent foodborne illness, particularly botulism.
A primary consideration is acidity. 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.
The processing method and time are equally critical. Always follow tested recipes from trusted sources such as the USDA 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. 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.
Use clean, undamaged jars and new lids to ensure a proper seal. After processing, jars should form a vacuum seal, indicated by a concave lid that does not flex when pressed. Maintaining the correct headspace allows for proper expansion during processing and helps achieve a secure seal.
Finally, storage and inspection are key steps. Store jars in a cool, dark and dry place, and label them 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.
By adhering to these key food safety considerations, canning can be performed safely while preserving the quality and shelf life of foods.
For more information, the MU Extension publication “Safe Home Canning Basics” is available for free download at
Related resources
These MU Extension publications are available for free download: