Janet Hackert, Nutrition and Health Education Specialist, Harrison County, University of Missouri Extension
For many years, boiling water canning has been the process used to safely can foods high in acid, whether naturally acidic like fruit, jams and jellies, or acidified foods like pickles or sauerkraut. University of Wisconsin Extension has released another tested process for safely canning high-acid foods: atmospheric steam canning.
Atmospheric steam canners use steam at 212 degrees Fahrenheit to heat food in jars inside the canner to the temperature needed to make it safe. But like boiling water canning, it is only a safe method if research-tested recipes are followed exactly. University of Wisconsin Extension does not recommend relying on the canning instructions in the booklet that comes with the canner.
Certain conditions must be met in order to can safely with an atmospheric steam canner. Some of these are the same as for boiling water canning:
Specific to atmospheric steam canning, the following conditions must also be met:
Because of this time limitation on steam canning, certain foods that are acceptable to can in a boiling water canner are not to be canned in a steam canner. A good example of this is whole or halved tomatoes packed in water or without added liquid. They require 85 minutes in a boiling water canner at 1000 feet elevation or lower. This far exceeds the capability of the steam canner’s 45-minute limit. Likewise, hot-packed crushed tomatoes canned in quarts at elevations of 1001-3000 feet require 50 minutes of processing, more than is recommended in an atmospheric steam canner.
As with boiling water canning, cool jars in still, room-temperature air. This natural cooling is part of the process to insure a safe, shelf-stable canned product.
With these conditions met, recipes and procedures for boiling water canning can be safely used in a steam canner. Reliable resources for recipes include University of Missouri Extension publications or the National Center for Home Food Preservation.
For more information on atmospheric steam canning, see Safe Preserving: Using an Atmospheric Steam Canner (a University of Wisconsin Extension publication).
You can also contact your local University of Missouri Extension office for answers to your questions, for publications or to find food preservation classes near you.