By Cassidy Hobbs Hall
Area Agent, Family and Consumer Sciences
Johnston County Cooperative Extension
When canning your own foods at home, there are a variety of factors that lead to great (or poor) quality products. Some of the most common problems I hear about from “seasoned” food preservers are jar seal failures. Jar seal failures can result from things like improper processing times, improper headspace, and improper handling of jar lids to name a few. Here are a few tips to ensure the best home-canned products:
- Stop boiling jar lids prior to use. Boiling the jar lids used to be the correct care method, however, lids today are intended for a single use. Boiling jar lids causes the wax compound to melt during the boiling process, which means their single use is used up. Handwash them prior to use to avoid melting the compound before they are placed on the jars.
- Stop ‘boiling the jars’ when canning vegetables and meats. There are two very different methods of canning. A waterbath canner is intended to heat jars by boiling, and is safe when canning foods with higher amounts of acid, such as fruits, foods with added vinegar or lemon juice, or fermented sauerkraut. A pressure canner must be used for foods without lots of acid, such as vegetables (yes, including green beans), meats, and even tomatoes that do not have lemon juice added. These foods must be pressure canned in order for the center of the jar to reach 240 degrees for a specified length of time based on the food composition, and the only way to accomplish this is by trapping steam inside of a pressure canner.
Steam gets trapped in a pressure canner and increases the temperature beyond the boiling point of 212 degrees. You’ll be able to monitor pressure inside the canner, but if you use a dial gauge pressure canner, be sure to have the dial gauge tested for accuracy each year. You can contact the Extension office for this free service. Pressure canning is essential for low acid foods, including tomatoes without added acid. Tomatoes today are less acidic than years ago, which heavily influences canning recommendations.
Keep in mind that if you waterbath can low acid foods, your jars may seal; however, the food inside will likely spoil or could cause Botulism, a serious foodborne illness. Spoilage and risk of foodborne illness occur as a result of pathogen growth. Pathogens that were on the food can grow and result in spoilage or sickness when acid is absent and food does not reach the correct temperature- which is based in-part on the acid content of the food. In essence, low acid foods should be pressure canned; high acid foods should be waterbath canned.
- Quality in is quality out! Nothing magical happens to foods when they are canned. If you are choosing bruised, unappealing produce to go into your jars, the quality you get out of those jars will remain the same, perhaps even worse. When foods that have bruises are canned, this is a perfect opportunity to introduce spoilage bacteria into your canned foods which can lead to major smells and food waste upon opening the jar.
- Get the air out. This tip may seem common sense when thinking about creating a shelf-stable product, but failure to process jars for the correct amount of time can leave oxygen in the jar. If this happens, the heating and cooling process will cause the lid to seal (see tip number one) to your jar, but that does not ensure all of the oxygen has left the jar.
Remaining oxygen is the perfect environment for food spoilage pathogens to grow! When filling your jars, be sure to move the food around and fit as much food into the jar that you can to squeeze out any trapped air. Take a straw or stirring tool to move things around and release unwanted air. Finally, be sure you do not have too much headspace. Your recipe should indicate how much space to leave between the top of the food and the top of the jar (see next tip).
- Ensure correct headspace. This point deserves to be its own tip! Too much headspace is a major issue. Each recipe’s processing time is determined based on factors including how much time it will take for the heat of processing to drive out oxygen. Too much headspace for the processing time results in seal failures and trapped oxygen, leading to spoilage. Too little headspace can also lead to jar seal failures because food gets pushed under the lid during processing and expansion, ruining the lid’s contact with the mouth of the jar.
Family heirloom recipes can be sweet reminders of the past, but when it comes to canning recipes, it is always a good idea to cross-reference recipes and procedures with the latest safety and food quality information! Contact the Johnston County Cooperative Extension Office at 919-989-5380 for classes, recipes, gauge testing, and information.
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