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How Does Canning Work?
Basically, when you heat up the filled, sealed jars, it causes the foods to expand and give up steam, pushing air out of the jars. When cooled, it forms a vacuum seal on the jar. Things that can affect canning and shelf life are the sugar content and acidity, it’s best to follow a canning recipe when first starting to help decide which method is suited towards the the food you will be canning.
2 Home Canning Methods
- Water bath canning. This method is a lower temperature canning process, ideal for high-acid foods and recipes that incorporate the correct measure of acid. It is recommended for fruits, jams, jellies, salsa, tomatoes, pickles, chutneys, sauces, pie fillings, and condiments.
- Pressure canning. This is a high temperature method needed to safely preserve low-acid foods. It’s recommended for meats, poultry, vegetables, chili, and seafood. The USDA advises against using a pressure cooker for canning because there are too many different models wtih varying results.
What Do You Need to Can at Home?
- Jar lifter Tongs: Tongs help to pick up hot jars and safely take them out of hot water after processing.
- Ladle: A ladle helps to spoon food into canning jars.
- Wide-mouth funnel: A wide-mouth funnel has a larger opening to fit jars. It makes it a cleaner task to fill your jars and keeps the rims cleaner.
- Canning jars and seals: Use glass mason jars with sealed lids. Ball mason jars are recommended.
- Large pot or water-bath canner: If you are mainly focusing on fruits, jams, jellies, pickles and salsa a water-bath canner or large pot will work great.
Tips for Getting the Most Out of Homemade Canning
- Use fresh produce. Can your fruits and vegetables when they are in peak condition, any bruised or overripe produce should be avoided.
- A boiling water bath or pressure canner? Acidic foods like pickles, preserves and tomatoes may be preserved in a boiling water bath. But non-acidic foods like soup stocks, unpickled vegetables and meat must be canned in special equipment, called a pressure canner.
- Fill the jars while they are still hot. Pack hot food into jars one at a time, leaving room at the top for closure. Place it back in the simmering water once it’s been filled.
- Listen for popping sounds. Once the jar has properly sealed, you should hear a popping sound and the lid should no longer pop up.
- Overfilling jars. A good recipe will instruct you to leave headspace between the surface of the food and rim of jar. If you fill jars too high, the canning lids will not seal properly. Unsealed jars aren’t dealbreakers, you can transfer it to a refrigerator to use within a few days, or reprocess with enough head space to seal.
What Is the Shelf Life of Canned Goods?
As a general rule of thumb, unopened home canned foods have a shelf life of one year when stored in a cool, dry place. For homemade jams made using sugar and processed by canning in a hot water bath, you can expect to get about two years of shelf life. Follow canning recipes for food safety.
How Do You Know if Canned Goods Have Gone Bad?
While most canning is shelf-stable, look for these indicators that the product inside the can has gone bad:
- A broken seal is a sign air has gotten in. A bulging lid can also be a sign of spoilage
- A lid that shows signs of rust or corrosion
- Bubbles when you open the can
- Food that has developed mold, or looks cloudy
- Food that gives off an unpleasant odor when you open the jar
Step-by-Step Guide: Basic Water Bath Canning
- Wash canning jars in hot, soapy water, and rinse. Place clean jars in a water bath canner or other deep, large pot. Cover with hot tap water and simmer over medium heat for 10 minutes. Keep them in hot simmering water until they are ready to fill. Place lids in a bowl and pour hot water from sterilizing pot over top. Once ready, remove one sterilized jar from water and place on a clean kitchen towel.
- Pour food into the jar using a ladle and funnel. Leave a ¼-inch headspace at the top.
- Release any trapped air bubbles by poking contents with a clean chopstick or wooden skewer.
- Wipe rims of jars with a clean, damp cloth and screw on lids.
- As you fill and close each jar, use a jar lifter to place it gently in the canner.
- Be sure that the jars do not touch each other, you made need to remove some water as you add jars to the pot.
- When all the jars have been placed inside, cover by 1-inch of water.
- Cover the canner and heat the water to a full rolling boil.
- Boil jars for 10 minutes (length of processing time may vary from recipe to recipe). Remove jars and place on a towel lined counter and let them cool to room temperature. You should hear the jars ping as soon as they’re removed from the pot. The sound is from the seals being formed, the center of the lids will become concave as the vacuum seal takes hold, creating an airtight seal.
- Once the jars are cooled, test seals by pressing center of jar lids. If the lid pops up and down, the jar isn’t sealed. Jars that don’t seal can be stored in the refrigerator and used within 3 days, or processed within 24 hours.
- Store jars in a cool, dry, dark place for up to 1 year (as recommended by National Center for Home Food Preservation).