06/12/2026
Canned foods are tradition-rich in many Midwest homes, where families have enjoyed the benefits of preserving fresh, often home-grown foods in airtight containers.
But the time-tested methods associated with canning fresh foods are not appropriate for leftovers or previously canned foods, said Kansas State University food scientist Karen Blakeslee.
“It may be tempting to can leftovers or already canned foods,” she said, “but it can be a food safety risk.”
For starters, Blakeslee notes that canning recipes and recommendations are based on fresh food that is prepared in a specific manner. “There is also the expense of jars, lids, time and energy to consider that adds up and is not very cost efficient,” she said.
Leftover food that is mishandled or temperature abused increases the food safety risks if bacteria are growing, according to Blakeslee. The canning process may not be adequate to kill bacteria.
“When recipes are developed, there are many safety factors involved, including the pH level, water activity, size of the food pieces, size of the jar, how the heat moves through the jar and food, the heat up and cool down time during processing, and much more,” Blakeslee said.
“Previously canned food or leftovers have a softer texture, which leads to a more dense product. Because of the variability of these foods, there are no standard recommendations to safely can these foods. It is not just about the lid sealing to the jar.”
The National Center for Home Food Preservation also reports that there are no safe, tested processes to can leftovers or foods that were previously canned. A default method – though not recommended – is to process the food for the full time and temperature as if starting from scratch.
“When you consider you are not saving money or resources, it does not seem worth the loss of food quality to practice this re-canning of commercially canned food,” Blakeslee said.
National Center for Home Food Preservation: https://nchfp.uga.edu/
RAPID RESPONSE CENTER: www.rrc.ksu.edu
