Home canning brings the flavors of each season to your pantry, but without the right precautions, it can also bring hidden dangers. Botulism, a deadly toxin caused by Clostridium botulinum bacteria, lurks in improperly canned foods and can lead to severe—even fatal—health risks¹.
As more people turn to canning, knowing how to avoid common mistakes is essential. Here are 15 canning missteps you must dodge to keep your preserves safe and delicious all year long.
1. Using Outdated Recipes
Grandma’s recipes might be treasured family heirlooms, but when it comes to canning, they could be a recipe for disaster. Old canning methods often lack the scientific testing required to ensure food safety. These outdated techniques may not account for changes in acidity levels of modern produce varieties or fail to eliminate harmful bacteria.
Stick to recipes from reputable sources that have been tested and approved by food safety experts. Organizations like the National Center for Home Food Preservation regularly update their guidelines based on the latest research.
By following these modern recipes, you’ll ensure your preserved goods are both delicious and safe to consume.
2. Skipping the Pressure Canner for Low-Acid Foods
One of the most dangerous mistakes in home canning is using a water bath method for low-acid foods. This shortcut can lead to the growth of Clostridium botulinum, the bacterium responsible for botulism – a potentially fatal foodborne illness.
Low-acid foods like vegetables, meats, and some tomato products require higher temperatures to eliminate this risk.
Always use a pressure canner for low-acid foods. The high-pressure environment allows the contents to reach temperatures well above boiling, effectively killing harmful bacteria. While it might seem like an extra step, this precaution is crucial for ensuring the safety of your preserved goods.
3. Overfilling Jars
It’s tempting to pack those jars to the brim, but resist the urge! Overfilling is a common mistake that can lead to seal failures and contamination. When jars are too full, the contents can expand during processing and push past the lid, preventing a proper seal.
Follow recipe guidelines for headspace – the gap between the top of the food and the rim of the jar. This space allows for the expansion of food during processing and the formation of a strong vacuum seal.
Typically, you’ll need to leave 1/4 to 1/2 inch for high-acid foods and 1 to 1 1/4 inches for low-acid foods.
4. Reusing Single-Use Lids
The allure of saving money by reusing canning lids is strong, but it’s a risky practice that can lead to seal failures. Single-use lids are designed with a special sealing compound that conforms to the jar rim during processing. Once used, this compound is compromised and may not create a reliable seal on subsequent uses.
Invest in new lids for each canning session to ensure proper sealing. While it might seem wasteful, the cost of new lids is minimal compared to the potential loss of food or risk of illness from improperly sealed jars.
If you’re looking for a more sustainable option, consider investing in reusable canning lids specifically designed for multiple uses.
5. Adjusting Recipes without Proper Knowledge
Adding extra onions to your salsa recipe or thickening your soup with flour might seem harmless, but these adjustments can have serious consequences. Altering tested recipes can change the acidity levels or density of the product, potentially creating an environment where harmful bacteria can thrive.
Stick to tested recipes without modifications. If you must make changes, consult with a food preservation expert or your local extension office. They can guide you on safe alterations or help you find a similar recipe that meets your needs while maintaining food safety standards.
6. Neglecting Altitude Adjustments
If you live at a high altitude, your canning process needs to be adjusted accordingly. Water boils at a lower temperature at higher elevations, which means your food may not reach the necessary temperature to kill harmful bacteria during processing.
Check your altitude and adjust processing times or pressure accordingly. For water bath canning, increase processing time by 5 minutes for every 1,000 feet above sea level. For pressure canning, increase pressure by 1 pound for every 2,000 feet above sea level.
These adjustments ensure your food reaches the proper temperature for safe preservation.
7. Using Damaged Jars
That tiny chip on the rim of your jar might seem insignificant, but it can spell disaster for your canning efforts. Damaged jars, including those with nicks, cracks, or uneven rims, can prevent proper sealing and may even break during processing.
Inspect each jar carefully before use. Run your finger along the rim to feel for any imperfections. If you detect any damage, set the jar aside for non-canning purposes.
Using only perfect jars will help ensure a proper seal and reduce the risk of jar breakage during processing.
8. Cooling Jars Too Quickly
After processing, it’s crucial to let your jars cool gradually. Rapid cooling, such as placing hot jars in cold water or a drafty area, can cause thermal shock. This sudden temperature change can lead to jar breakage or seal failure.
Allow jars to cool naturally in the canner. For water bath canning, remove the lid and let the jars sit for 5 minutes before removing them. For pressure canning, let the canner depressurize naturally before opening.
Once removed, place jars on a towel-lined counter away from drafts and let them cool completely before handling.
9. Skipping the Bubbling Step
Air bubbles trapped in your jars can interfere with heat distribution during processing and may lead to improper sealing. These pockets of air can also cause discoloration or spoilage of food near the top of the jar.
After filling jars, use a non-metallic utensil to remove air bubbles. Gently slide the tool between the food and the jar, allowing trapped air to escape. This simple step helps ensure even heating and proper sealing, leading to better preservation of your food.
10. Tightening Bands Too Much
It might seem counterintuitive, but overtightening your canning bands can actually prevent proper sealing. When bands are too tight, air can’t escape during processing, which is necessary for creating a vacuum seal.
Tighten bands to “fingertip tight” – just until you feel resistance. This allows enough air to escape during processing while keeping the lid in place.
Remember, the bands are only there to hold the lid in place during processing; the seal itself is created by the vacuum formed as the jar cools.
11. Processing for Incorrect Times
Underprocessing can lead to spoilage and potential food safety issues while overprocessing can result in mushy, overcooked food. Both scenarios waste your time and resources.
Follow processing times precisely as stated in tested recipes. Use a reliable timer and start counting only when the water is at a full rolling boil for water bath canning or when the correct pressure is reached for pressure canning.
Accurate timing is crucial for both food safety and quality.
12. Storing Jars with Bands On
Leaving screw bands on during storage might seem like added protection, but it can actually hide potential problems. A loosened lid might reseal itself if the band is left on, masking spoilage.
Remove bands once the jars have cooled completely and you’ve checked the seals. This allows you to easily spot any jars that have become unsealed during storage. It also prevents rust from forming on the bands, extending their usable life.
13. Ignoring Signs of Spoilage
Even with the best precautions, spoilage can sometimes occur. Ignoring or overlooking signs of spoilage can lead to serious illness. Common signs include bulging lids, leaking jars, off-odors, or visible mold.
Always inspect jars before opening and using them. If you notice any signs of spoilage, discard the contents without tasting. When in doubt, throw it out. It’s better to lose one jar of food than risk foodborne illness.
14. Using an Ordinary Pot Instead of a Proper Canner
A large stockpot might seem like a suitable substitute for a water bath canner, but it lacks crucial features for safe canning. Proper canners have fitted racks to keep jars off the bottom and allow for proper water circulation.
Invest in a proper water bath canner for high-acid foods and a pressure canner for low-acid foods. These specialized tools ensure even heat distribution and maintain the necessary temperature throughout processing.
The initial investment pays off in food safety and peace of mind.
15. Failing to Label & Date Jars
In the excitement of finishing a canning session, it’s easy to forget to label your jars. But unlabeled jars can lead to confusion later, especially if you’re canning similar-looking products.
Label each jar with the contents and date of processing. This helps you use older products first and ensures you don’t keep home-canned goods beyond their recommended storage time. Most home-canned foods are best used within a year for optimal quality.
Home canning is a rewarding practice that allows us to enjoy homegrown flavors throughout the year. However, it’s crucial to approach this tradition with knowledge and caution. By avoiding these 15 common mistakes, you’ll significantly reduce the risks associated with home canning and ensure the safety of your preserved foods.
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Nancy has been a plant person from an early age. That interest blossomed into a bachelor’s in biology from Elmira College and a master’s degree in horticulture and communications from the University of Kentucky. Nancy worked in plant taxonomy at the University of Florida and the L. H. Bailey Hortorium at Cornell University, and wrote and edited gardening books at Rodale Press in Emmaus, PA. Her interests are plant identification, gardening, hiking, and reading.