Canning safely requires a tested recipe
Canning has changed in the generations since your ancestors canned food. All safe food preservation begins with using tested recipes and properly working equipment. These recipes have been specifically designed to ensure a safe, quality product when followed exactly. Processing times may also vary depending on the product, size of jars used, and the altitude where you live. Find your altitude and read Extension's complete canning guide to safe canning methods.
Food preservation increases the shelf-life of food and keeps food safe. Microorganisms, such as molds, yeasts, and bacteria, cause food spoilage. These microorganisms can be found anywhere and can easily contaminate foods. Controlling the growing conditions for these harmful microorganisms is the best way to prevent food spoilage and decrease the risk of foodborne illness.
Start with the right canning supplies
Mason Type Jars
Always inspect jars before using. Jars may be reused but may become brittle, scratched, cracked, or chipped with repeated use, causing them to break during processing or preventing the lids from sealing. Only use glass jars designed for home canning, and make sure the mouth of the jar has screw threads on the outer perimeter. Jars with rubber gaskets are typically safe for fermented or refrigerated foods but not for canning.
Start with clean jars. Before every use, wash the empty jars in hot water with detergent and rinse well by hand or use a dishwasher.
Use self-sealing lids that work as part of a two-piece sealing system with canning rings (bands). The flat canning lids create the seal which keeps processed food safe. The lids are safe to use once but cannot be reused for canning purposes.
Rings or Bands
Rings screw onto canning jars after the flat lids have been placed, before processing. Rings on processed, cooled product may be removed for storage and reused as long as they are free of rust, dents, or other damage.
Use sterilized jars, bands, and lids for products that will be processed for less than 10 minutes. To sterilize, boil for 10 minutes in a boiling-water bath canner. Just before filling, carefully remove the hot, sterilized jars from the boiling water with tongs and fill them with the prepared product. Then use tongs to remove the lids and bands from the boiling water, place lids carefully on jars, and tighten the bands.
Unfilled space above the food in a sealed container and below the lid is called headspace and is needed to allow for the expansion of food while processing. The amount of headspace required depends on the type of food being processed. Starchy foods tend to expand and swell when heated, so make sure to follow the headspace recommendations from a tested recipe.
Test dial-gauge pressure canners annually to ensure accuracy. Many local Illinois Extension offices provide free pressure canner testing. Find the nearest testing location.
- If a pressure dial reads too low, a high enough temperature will not be reached to destroy the bacterial spores created by C. botulinum.
- If the pressure dial reads too high, over processing will occur and
impact both the quality and texture of the product.
- Replace pressure dial gauge if it is off by more than two pounds.
- Thoroughly clean lid after each use, keeping it free of food and hard water residue.
- Clean edges of lid and inspect vent port (steam vent) to ensure it has not become plugged.
- Inspect gaskets for cracks. Replace brittle gaskets or gaskets that do not fit properly; they will not be able to maintain a seal.
- A proper seal is critical to ensure a high enough temperature will be reached to destroy the bacterial spores created by C. botulinum.
- Purchase new seals at hardware and home improvement stores or by contacting canner manufacturers.
References and Resources
- CDC. Home Canning and Botulism
- National Home Center for Home Food Preservation. General Canning Information
- National Home Center for Home Food Preservation. How Do I? ...Can Vegetables.
- So Easy to Preserve, 6th Edition: setp.uga.edu
- USDA Complete Guide to Home Canning
- The Ball ® Blue Book Websites and Online Videos
- What’s Cooking with Mary Liz Wright
- Illinois Extension. From Garden Gates to Dinner Plates:
- Illinois Extension. Food Preservation