Jon Cofer, Penn State University
To safely can low acid foods, you must use a pressure canner. This includes all vegetables, except acidified tomatoes, meats, fish, and poultry. Whether you have a dial gauge or weighted gauge canner be sure to check the following:
- For dial gauge canners, have the gauge checked for accuracy every year.
- Be sure the rubber gasket is flexible and soft, not brittle, sticky or cracked.
- If the rubber gasket needs replaced, identify the brand and model number of your canner before purchasing a replacement online or at the store. If going to the store there are many styles of gaskets available, and you will not be able to judge the thickness and size of the rubber gasket by sight.
- Check the pliability of the washer on the air vent and the pressure release plug.
- Hold the lid to the light to make sure any small pipes or vent ports with openings are clean and open all the way through. Clean vents with a small brush or a pipe cleaner as needed.
Water Bath Canning
Use a boiling water bath canner or an atmospheric steam canner for canning fruits, pickles, acidified tomatoes, jellies and jams. A boiling water bath canner should be deep enough to allow at least one to two inches of water to boil vigorously above the tops of the jars. All canners should have a rack in the bottom to keep jars off the bottom of the canner. It may be a flat rack or a lift out type rack.
Inventory your jars and decide if you need to buy new jars. Inspect them for nicks, cracks, or chips--especially around the top sealing edge. Nicks can prevent lids from sealing. Very old jars can weaken with age and repeated use and may break under pressure and heat. New jars are a better investment over time than buying used jars at yard sales or flea markets. Use mason jars specifically designed for home canning. Although canning jars come in a variety of sizes from one half-cup to one half-gallon, processing times have not been developed for many foods in half-pint, 12-ounce, or 24-ounce jars. If a recipe does not specify a processing time for one of these jars, process according to the time given for the next larger jar. Half-gallon canning jars are only suitable for very acidic juices such as apple juice and grape juice.
Use two-piece lids consisting of a flat metal disc, which has a sealing compound around the outer edge and a separate metal screw band. This is the only type recommended by the USDA. Always use new flat lids. The screw bands are reusable if they are not bent, dented or rusted. Do not reuse lids from commercially canned foods for home canning.
Other items to making home canning easier include:
- Jar lifter, essential for easy removal of hot jars from the canner.
- Wide mouth funnel helps in packing small food items and jams into canning jars.
- Plastic bubble freer removes air bubbles from jars. Do not use metal knives or other metal objects as they can scratch the glass making the jar more susceptible to breakage.
- Lid wand has a magnet on the end that helps remove lids from the hot water.
- Timer or clock to determine the end of the processing time.
Finally, make sure that you have up-to-date canning instructions. See Penn State Let's Preserve articles for more information. The USDA Complete Guide to Home Canning was last updated in 2015. Canning books published prior to 1994 will not have safe processing times and/or methods. The National Center for Home Food Preservation offers canning information and research tested canning recipes.
Planning ahead can save you time, money, and frustration. Make it a happy, successful canning season by getting prepared before your harvest is ready.