Are steam canners safe to use?



Due to the lack of definitive research regarding the safety of steam canning, USU Extension researchers agree with the present USDA and National Center for Home Food Preservation recommendation against using steam canners. The USDA Complete Guide to Canning states, “Steam canners are not recommended because processing times for use with current models have not been adequately researched.”

Steam canning should not be confused with boiling water canning. Steam canning requires a special canner to boil water and make steam. The theory is that steam canning uses less water and reaches temperature in a shorter time than a boiling water canner. A boiling water canner is a large pot where jars are submersed in boiling water by at least 1 inch of water.

It has been Extension researchers’ experience that many consumers are using steam canners despite recommendations against their use. For those consumers who still use steam canners against recommendations, Extension researchers firmly advise against steam canning low acid (e.g., vegetables) or borderline acid foods (e.g., tomatoes). Under-processing these foods can lead to botulism food poisoning.

For acid foods such as fruits, jams or jellies, there is not a risk of botulism. However, under-processing can lead to food spoilage in these types of foods. Preliminary research has indicated that these six steps will help decrease the chances of under-processing acid foods in a steam canner.

Place appropriate amount of water in the base. Place the perforated cover over the base and bring water to a low boil.

2. Pack and fill jars. Secure lids firmly, but not over-tight. Set each full jar on the base and allow it to warm while packing and filling enough jars for one batch.

3. When the last full jar has warmed for 1-2 minutes, place the dome on the base and slowly (4-5 minutes) increase temperature setting of the stove until a column of steam 8-10 inches is evident from the small holes at the base of the dome.

4. Begin timing the process, maintaining the column of steam following the water bath canning recommendations adjusted for your altitude. Do not reduce temperature setting of the stove. The dome should not bounce from the base during processing. Do not allow water reservoir to boil dry. If the column of steam ceases, then the process was not successful, and you will need to start over.

5. When processing time is complete, turn stove off and wait 2-3 minutes before removing the dome. Remove the dome by turning it away from your face and body to avoid burns.

6. Allow jars to cool and seal. Remove metal bands and store the jars in a cool, dark place.

It is hoped that in the years to come, sound scientific studies can define a safe steam canning process and processing parameters. Until that time, it is best to avoid this process until researchers can fully determine it is safe to use.

Posted on 16 Sep 2005

Brian Nummer
Food Safety Specialist

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