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.

In recent decades, atmospheric steam canning has not been recommended for home food preservation. However, recent studies have been published that no longer condemn steam canners. The University of Wisconsin-Madison has published research confirming that atmospheric steam canners are acceptable to use for preserving naturally acidic foods, or acidified-foods such as salsas or pickle varieties. The research comes with assurances that this tool can be used, with conditions that need to be controlled first, such as the following:

High Acid

Foods must register at a pH of 4.6 or below. This includes fruits such as peaches, pears and apples. This method is not suitable for vegetables or meats that generally fall into lower-acid categories. It is not recommended to use a steam canner for tomatoes. The exception is for products such as salsa where additional acid is used.

Approved Recipe Use

A research-tested recipe must be used with the atmospheric steam canner. Approved recipes can be found on websites such as the USDA Complete Guide to Home Canning, and the National Center for Home Food Processing and Preservation: nchfp.uga.edu. Standard canning jars and two-piece lids are required. An atmospheric steam canner is approved for use with recipes approved for half-pint, pint or quart jars.  

Pure Steam at 212°F

Prior to processing, canners must be vented until a full plume of steam appears. A plume of steam approx. 8 inches coming from the sides of the canner should be visible throughout the entire processing time. When purchasing a steam canner, be aware of features such as a built-in temperature sensor in the lid. The canner should remain at a steady 212°F temperature.

Time is of the Essence

Processing time needs to be adjusted for elevation as required by a tested recipe. The USDA guide is a reliable resource to determine the amount of added processing time needed. With this in mind, processing times must be limited to 45 minutes or less. This includes time modifications for elevation. Time is limited due to the amount of water in the base of the canner. While food is processing, water should not be added. If the heat temperature is too high, water can boil dry before processing is complete, and this is deemed unsafe.

Jar Care

Jars must be heated before adding product or processing. It is important not to let much cooling occur prior to processing. After processing, jars should be placed on a rack or towel away from drafts and not force-cooled.

This article was written by Erin Floyd, Intern with USU Extension, and Mealanie D. Jewkes, Extension Associate Professor, Utah State University Salt Lake County Extension.

Source: http://nchfp.uga.edu/publications/nchfp/factsheets/steam_canners.html