Do not can tomatoes that have been on the vine during a frost or freeze, says K-State food scientist Karen Blakeslee. (File photo)
Enjoy safely preserving sweet potatoes and tomatoes for fall
K-State food safety expert shares tips and safety precautions for home canning
Sept. 30, 2021
By Taylor Jamison, K-State Research and Extension news writer
MANHATTAN, Kan. – With the arrival of fall, many people enjoy canning their produce to enjoy during the colder months and holidays.
Two common canned favorites during fall are sweet potatoes and tomatoes. Kansas State University food scientist Karen Blakeslee shares tips and safety precautions for home canning.
She says that food preservation by means of canning is backed by years of science and was a much-utilized method in times where food was scarce for the fall and winter seasons. However, despite food preservation’s time-backed safety, older recipes may not be ideal.
“The science is evolving, so over the years the recommendations to preserve food safely have evolved,” said Blakeslee, who is also coordinator of K-State’s Rapid Response Center for food science. “Food preservation methods and practices of yester-year may not be safe for today.”
To ensure food safety, Blakeslee advises only using recipes that are up-to-date. While sweet potatoes and tomatoes are vegetables, the two foods differ in their acid content.
Sweet potatoes are a low-acid food. Blakeslee said the canning requirements for sweet potatoes include:
- Pressure canning to get the temperature up to 240°F to destroy the dangerous food pathogen, Clostridium botulinum.
- Cut potatoes into chunks or pieces, do not puree or mash. Heat cannot move adequately through the jar with a dense mash.
Tomatoes are in between a low-acid and high-acid food, and Blakeslee outlines the different canning requirements:
- Do not can tomatoes that have been on the vine during a frost or freeze. The acidity has changed throughout the temperature change and bacterial pathogens are more likely to have invaded.
- Tomatoes that are overripe may also not be ideal to can, as a tomato’s acidity decreases as they mature – again, making bacteria more likely to grow. Ensure correct canning temperatures are reached to kill bacteria.
- Tomatoes not subjected to a frost or freeze can be safely canned using a pressure canner or water batch canner. With either method, extra acid must be added to ensure safety.
After your produce is canned, there are still a couple safety measures to consider.
“Store canned food in a cool, dry, dark location and use within one year,” Blakeslee said.
Blakeslee recommends using Kansas State University’s resources for safe food preservation and trusted canning recipes. “Remember to adjust your processing for your location to account for higher elevations,” said Blakeslee, who recommends consulting this elevation guide.
Blakeslee publishes a monthly newsletter called You Asked It! that provides numerous tips on being safe and healthy. More information is also available from local extension offices in Kansas.
