Grandma used a steam canner all summer long, but you’ve heard they are not safe. Read up on what the latest research has to say about steam canning.

For decades, home food preservers have been told that boiling water-bath canners were the only approved way to process high acid foods (fruits, pickles, jams and jellies). The main reason for the recommendation was because there had not been adequate research performed on steam canners to the satisfaction of food preservation specialists at USDA and the National Center for Home Food Preservation (NCHFP).

In an article published in Food Protection Trends titled, “Atmospheric Steam Canners Can Provide a Safe Alternative to Boiling Water Canning for Acid Foods,” authors including Drs. Barbara Ingham, University of Wisconsin, and Elizabeth Andress, Director of the NCHFP, provide the conditions and guidelines for safely using steam canners at home. These are summarized below.

1- Process only food products that are high in acid in an atmospheric steam canner; the food pH must be less than or equal to pH 4.6. Low acid foods (including meat and vegetables) must still be processed using a steam pressure canner.

2- Use a current, research-tested recipe developed for boiling water canners with steam canners. Approved recipes may be found in the USDA Complete Guide to Home Canning, at the National Center for Home Food Processing and Preservation (nchfp.uga.edu) or in the Ball Blue Book Guide to Preserving but not in atmospheric steam canner instruction booklets. Factsheets and booklets produced by University Extension offices throughout the country are also approved when they reference one or more of these sources.

3- Monitor temperature in the steam canner to make sure that the process time begins only when the temperature of pure steam is reached. To better facilitate this, some steam canners are equipped with a built-in temperature sensor in the dome lid. Note that 212 F cannot reached at high altitudes without the use of steam under pressure. Therefore, additional processing time is required to effectively kill harmful bacteria/micro-organisms.

4- Heat jars prior to filling. Keep jars hot prior to the start of the processing time. To minimize cooling of jars, preheat both steam canners and boiling water canners before adding hot jars filled with food.

5- Make altitude adjustments. For elevations above 1,000 feet, the increased processing times recommended in research-tested recipes for boiling water canners should be followed.

6- To prevent the canner from boiling dry, limit processing time to 45 minutes or less. This exempts many tomato products —  especially those in quart-sized jars. Consumers must not open the canner to add water during the process; doing so will lower the temperature and may result in under-processed, unsafe food.

7- Cool jars in still, ambient (room) temperature air. Most microbial kill occurs during air cooling; thus the cooling procedure is extremely important. Do not cool jars in water, in the refrigerator, in front of a fan or by hastening the cooling process in any other way.

To access the complete article describing safely using atmospheric steam canners, visit http://nchfp.uga.edu/publications/nchfp/factsheets/steam_canners.html. If you have further questions regarding any of the above guidelines, please contact your local USU Extension Office.

Kathleen Riggs is the Utah State University Extension family and consumer sciences professor for Iron County. Questions or comments may be sent to kathleen.riggs@usu.edu or call 435-586-8132.