K-State Research and Extension

Preservation

Canning, freezing and drying food at home are great ways to preserve fresh food for later use. The key is canning, freezing or drying food properly and safely to prevent foodborne illness.

10 Tips for Safe Home-Canned Food

Home-canned foods are a year-round treat. But if those foods are not canned safely, foodborne illness can turn a treat into tragedy. Use current canning methods and follow these tips to can food safely or check with the publication 10 Tips for Safe Home-Canned Food.

1. Altitude Adjustment - Kansas altitude can range from below 1,000 feet to just over 4,000 feet. Failure to adjust for altitude will lead to underprocessed food, which encourages the growth of Clostridium botulinum. Recipes in the USDA Complete Guide to Home Canning give altitude information with each recipe. Recipes in books such as So Easy to Preserve, Ball Blue Book and Ball Complete Book to Home Preserving are written with processing instructions for altitudes below 1,000 feet. Always read the general instructions in these resources for more information.
2. Headspace - Proper headspace helps ensure a good vacuum seal on jars. too little headspace can compromise the seal. Food and liquid expands during processing and may seep underneath the sealing compound. Too much headspace leaves excess air inside the jar, causing discoloration, seal failure and spoilage.
   • Recommended Headspace:
     • Jams and Jellies - ¼ inch
     • Fruits, Pickles and Tomato Products - ½ inch
     • Vegetables - 1 inch
     • Meats and Poultry - at least 1 inch
   • For best results always follow headspace measurements in the recipe.
3. Processing Equipment - Processing methods are recommended for home canning are water bath canners for high-acid foods and pressure canners for low-acid foods. The following old methods are NOT recommended and may cause spoiled food and foodborne illness:
   • Open Kettle Canning - In this method, hot food is poured into jars and the lid and ring are applied with not further heat processing. This allows bacteria, yeast and mold to grow and spoil food. Examples include inverting hot jars and sun canning.
   • Oven - Oven temperatures vary with the accuracy of oven regulators and air movement. Dry heat moves slowly through jars, allowing bacteria to grow. Jars may crack due to temperature shock.
   • Dishwasher - Use the dishwasher to wash empty jars and keep them hot. Do not use it for processing filled jars. The water temperature is not high enough to kill bacteria for safe canning.
4. Untested or Homemade Recipes - Canning your favorite recipe is risky, and may cause spoilage and foodborne illness. It is difficult to determine the safety of a homemade recipe without having detailed knowledge of the recipe, preparation procedures, total acid content and consistency of the final product. Use test recipes from trusted resources such as USDA, K-State Research and Extension Publications or home preserving equipment and ingredient manufacturers. Commercially canned foods are rigorously tests for safety. It is dangerous to try to recreate them at home.
5. Acidifying Tomatoes - Tomatoes are on the borderline between a low-acid and high-acid food. Tomato processing recommendations include both boiling water and pressure canning. Pressure processing instructions are equivalent in heat treatment to water bath processing. Both methods require acidification. There are no recommendations to process tomatoes without acidification.
   • Acidification Options for Tomatoes (Choose One)
     • Pints
       • Bottled Lemon Juice - 1 tablespoon
       • Citric Acid - ¼ teaspoon
       • Vinegar (5% acidity) - 2 tablespoons)
     • Quarts
       • Bottled Lemon Juice - 2 tablespoons
       • Citric Acid - ½ teaspoon
       • Vinegar (5% acidity) - 4 tablespoons
6. Improper Processing Time - Use trusted resources for safe processing instructions. Guessing can lead to underprocessing and foodborne illness or to overprocessing and poor quality food.
7. Lids and Jars - Recipes specify what size of jar to use. If a recipe lists pints only, do not use a larger jar. Regular and wide-mouth Mason-type, threaded, home-canning jars with self-sealing lids are the best choice. With careful use and handling, Mason jars may be reused many times. Colored jars and lids are available and safe for canning. Commercial jars, such as mayonnaise jars, can be used for high acid foods and water-bath canning. You must use the two-piece lid and ring, which may not fit the jar rim. Commercial jars cannot accommodate two-piece canning lids are not recommended for home canning. The common self-sealing lid consists of a flat metal lid and a metal screw band. These lids are used one-time only. Reusing metal lids can lead to seal failure and spoilage.
8. Modifying Tested Recipes - Adding thickeners, pasta, rice or any other ingredient to tested recipes can result in spoilage or foodborne illness. These changes alter the acidity and consistency, which slows heat penetration. Instead, make the recipe as stated then add extra ingredients before serving.
9. Fancy Pack - Fancy packs are not practical and produce potentially unsafe products. Processing times depend on specific preparation procedures. For example, preparation instructions specify cutting carrots into pieces, instead of packing them whole. Fancy packs can slow heat penetration through the jar of dense food. The slow process of fancy packing hot food will cool the food too much, resulting in underprocessing.
10. New Appliances for Home Canning -Food preservation manufacturers are selling new appliances to help consumers preserve food without  a lot of expertise or in smaller batches. These appliances must be used according to their instructions and recipes. Use of recipes not developed for these appliances can lead to seal failure, food spoilage and other potential health risks.