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Canners and Canning Methods that are Not Recommended

There are some methods that have been determined to be unsafe and are not recommended. Some of these unsafe methods include steam canners, solar canning, oven canning, open kettle canning, microwave processing, and dishwashing processing.

Steam Canners

Steam canning guidelines have been updated (June 2015). The University of Wisconsin has  published research which indicates that an Atmospheric Steam Canner may be safely used for canning naturally acid foods such as peaches, pears, and apples, or acidified-foods such as salsa or pickles, as long as specific criteria are met.

Solar Canning

The heat generated from captured sunlight is not a reliable method to process acid foods and should never be used to can low-acid foods.

Oven Canning

Oven Canning is extremely hazardous. The oven canning method involves placing jars in an oven and heating. In oven canning, product temperatures never exceed the boiling point because the jars are not covered. It is, therefore, not safe to use for low-acid products (e.g. meats, most vegetables) which require temperatures higher than 212°F.

Oven canning is not a recommend process. The glass jars are not designed to withstand the intense dry heat and may shatter in the oven. There is also the danger of breakage and burns while removing them from the oven.

Also, and most importantly, the transfer of heat into the jars is much slower through air in an oven than in a water bath or a pressurized steam canner. The recipes that we recommend have been scientifically tested using a water bath or pressure canner and should be followed exactly as written. Otherwise there is a heightened risk of spoilage, or worse, survival of Clostridium botulinum spores, the source of deadly botulism poisoning.

Open Kettle Canning

The open-kettle method involves placing hot food in jars and sealing with no further heat treatment. This method is not recommended for home canning because the amount of heat applied may not be sufficient to destroy bacteria and the product may spoil quickly or cause illness when consumed.

Microwave Processing

Microwave oven cannot be used for home canning. Microwaved food reaches 212°F but heating is not uniform. There is also a danger of explosion of the jars within the microwave oven or as food is being removed from the oven.

Micro-Dome Food Preserver

Micro-Dome Food Preserver Recalled Washington, DC--The U.S. Consumer Product Safety Commission (CPSC) in cooperation with Micro-Dome of San Ramon, CA, has warned consumers of certain safety hazards associated with the use of the "Micro-Dome Food Preserver" manufactured by Micro-Dome and sold and distributed to consumers after August 1987. The CPSC has also urged consumers to destroy all food that has been preserved using a Micro-Dome Food Preserver

Dishwasher Processing

Processing canned foods during a dishwasher cycle can be dangerous. The temperature of the water during the cleaning and rinsing cycle is far below that required to kill harmful microorganisms. Thus the product will be under-processed and unsafe to eat.

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Canners and Canning Methods that are Not Recommended

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Contact Information

Luke LaBorde
  • Professor of Food Science - Plant Based Products.
Email:
Phone: 814-863-2298