Canning mistakes can be DEADLY

Linda Beech is Ellis County Extension Agent for Family and Consumer Sciences with Kansas State Research and Extension.

Linda Beech

The canning kettles at my house have been steaming this time of year. I’ve been canning green beans from my garden and last night I made several jars of pickle relish. I can’t wait until the pears and peaches and apples are ready to preserve in their time.

I am a canning enthusiast and I love to help people learn to preserve food properly and safely. However, I was surprised at the number of errors I noted while judging food preservation exhibits at two recent county fairs. One of the biggest mistakes was the assumption that a sealed jar lid is the only goal – that as long as the jar is sealed, the food inside is safely preserved no matter how the food was handled or processed.

That assumption can be wrong– maybe DEAD wrong.

“Just because the lid sealed, it doesn’t guarantee that it’s safe.” It’s a phrase I repeated numerous times during the fair judging.

A jar lid seals when the oxygen is driven off with heat and a vacuum seal is formed. This creates the ideal environment for the growth of the deadly botulism bacteria which grows only in the ABSENCE of oxygen. The food must be heat-treated to temperatures hot enough and long enough during canning to kill botulism spores or otherwise the sealed jar may become a dangerous food safety hazard.

The only methods recommended for canning foods at home are boiling water bath canning for high-acid foods and pressure canning for low-acid foods. Following tested, research-based instructions from reliable, up-to-date resources is vital to ensure that the foods are processed properly for safety.

Old-fashioned methods like open kettle canning or unusual techniques like canning in the oven, sun or dishwasher might set a seal, but remember– just because the lid seals there is no guarantee the food inside will be safe without adequate heat processing.

Likewise, using untested canning information from online recipe-sharing sites or outdated books may be a recipe for disaster. It takes precise scientific testing to determine the right amount of time and heat needed for each food to reach adequate processing temperatures.

The latest science-based canning guidelines also recommend adjusting processing time and/or pressure for altitude– usually more time and higher pressure settings for higher elevations.

Kansas altitudes range from below 1,000 feet to just over 4,000 feet, so knowing your altitude is critical for making required adjustments. Most Ellis County locations are at about 2000 feet in elevation, requiring pressure canning at 11 or 12 pounds pressure instead of 10 and adding time to boiling water bath canning methods (follow specific canning guidelines for each food.) Not adjusting for altitude will lead to under-processed food, which can allow for growth of the botulism bacteria.

Once again, just because the lid sealed, it doesn’t guarantee the food is safe without proper processing for your altitude.

Canning is an enjoyable kitchen activity, but it is one based more in science than in art. Tested canning recipes must be followed exactly for the product to be safe.

Canning time is not a time for personal creativity!

It is unsafe to make up or modify canning recipes by changing ingredients, processing times or even canning jar sizes.

Salsa is a perfect example– did you know there are no reliable tested guidelines for canning salsa in quart jars? And yet, I saw several quarts of salsa at the recent fairs where I judged. And talk about recipe creativity– salsa is the prime example of a canned product that people love to change to suit their family tastes or available ingredients. Don’t be tempted to tinker with a standard salsa canning recipe or use one from the internet or shared by a friend. Remember my mantra– just because the lid seals, it doesn’t guarantee that a modified recipe will be safe.

Home-canned foods are a year-round treat. Canning can stretch the grocery budget while making use of fresh, local food. But, if canned foods are not handled properly, serious foodborne illness can turn a treat into tragedy. Use up-to-date canning procedures from reliable, research-based sources and follow instructions exactly for best results. Because– repeat after me– just because the lid sealed, it doesn’t guarantee that it’s safe!

Linda K. Beech is Ellis County Extension Agent for Family and Consumer Sciences

  • Geni

    On one canning blog, I read that steam canners are now approved for high acid foods. I can’t find any confirmation from Ball or National Center for Home Food Preservation. Is there any truth to this?