Say No to Oven Canning

History of Oven Canning

Simply described, oven canning is filling mason style jars with food (with or without a lid) and then heating (baking) them in the oven rather than processing in a water bath or pressure canner. According to How Did We Can? The Evolution of Home Canning Practices from the USDA National Agricultural Library, this method of canning was popular in the early part of the 1900's as it did not heat up the kitchen like canning foods in a water bath canner and there was a reduced risk for steam burns. However, after further study, by the end of World War II USDA noted that “oven canning is influenced by so many variable factors that it cannot be recommended as a safe method of food preservation." As a result, they revised their publications to reflect water bath or pressure canning as the only safe methods for home canning of foods.

Why Do People Continue to Oven Can?

Even though our understanding of the science involved in safely canning food at home has grown, it is hard to change habits handed down through generations. Some of the reasons Extension educators hear for using this method include:

• My grandmother/mother/aunt have done it for years and no one ever got sick.
• My next-door neighbor said she read about it on the internet, and it seemed easy to do.
• We have an old book with recommended canning times that we use.
• I do not want to heat up my kitchen.

Why Oven Canning is Not Safe

Canning is a safe method of food preservation when research-based, and tested practices are used. Based on the type of food being preserved the product must be processed in a water bath, atmospheric steam, or pressure canner. The National Center for Home Food Preservation cites many reasons why oven canning is not safe.

• There are no research-based process guidelines for oven canning that will ensure a safe final product.
• Mason style jars are not tempered to be used in the oven. Jars can explode in the oven causing damage to the oven or injury from broken glass.
• Oven temperatures vary according to accuracy of the oven regulators and circulation of heat. Oven heat is dry and slow to penetrate the jar. As a result, the processing times for water bath or pressure canning will not apply.
• The oven temperature is not the same as the temperature of the food in the jar. Think about cooking a roast. You may set the oven temperature to 325°F but do you cook the roast to a final internal temperature of 325°F? If you did how long would it have to cook to reach that temperature? There are no research-tested guidelines for canning food in the oven, therefore we do not know if the food in the jar is reaching the temperatures needed to destroy spoilage microorganisms and other bacteria, such as Clostridium botulinum.
• Eating improperly canned low acid foods can cause botulism, a deadly foodborne illness.

Oven canning may have been a common home food preservation method years ago, however, science has demonstrated that it is not a safe practice. While it may seem easier or is the latest trend on popular media sites, there are no shortcuts when it comes to safely canning food. Always use reliable sources based on USDA and National Center for Home Food Preservation guidelines and follow directions exactly.

References

National Center Home Food Preservation. (August 2020). FAQ: My neighbor gave me green beans that were canned using the oven method.

USDA National Agricultural Library. (n.d.). How Did We Can? The Evolution of Home Canning Practices.