Using steam canners to process high-acid or acidified foods (SP50-1005)

Foods that are naturally high in acid — including most fruits and acidified foods, such as pickles and salsas — may be processed in a steam canner. Most tested recipes for processing high-acid foods in a boiling water canner may be adapted for use in a steam canner by using these instructions.

Steam canners process jars in pure steam, so they need less water than boiling water canners. A typical boiling water canner might take 16 quarts of water to fill, while a steam canner only uses about 2 quarts of water. With less water to heat, the steam canner takes less time to come to a boil so processing is more efficient.

Steam canners come with a shallow bottom, a wire rack and a domed lid with vent ports. Some models come with a temperature gauge built into the handle. Only the Victorio and Back-to-Basics brand dome-style steam canners have been independently tested. Please check with the manufacturers regarding the safety of other brands and models.

CAUTION: Use care while using the steam canner as the steam and water can cause serious burn injuries. The highest risk is when opening the steam canner after processing. Tilt the lid away from you when opening to avoid steam burns.

Considerations

Always use an up-to-date, tested recipe and follow the instructions for proper processing contained in this bulletin.

NOTE: Steam canners often come with a recipe book with processing instructions. These instructions are not based on current research-tested methods and may lead to underprocessing. Foods processed following the steam canner instructions may not be safe or may spoil.

Jars are processed in pure steam, which is 212°F at sea level. Because water has a lower boiling point at higher altitudes, processing times must be adjusted. Add 5 minutes of processing for every 1,000 feet above sea level.

Do not use a recipe that calls for a processing time longer than 45 minutes, including time adjustments made for altitude (see above). If the processing time is too long, the steam canner can boil dry and the food would be underprocessed. Therefore, processing in steam canners is limited to products with shorter processing times.

For example, you should not use a steam canner to process raw packed whole or half tomatoes (in pints or quarts) because the processing time in a boiling water canner at 0–1,000 ft is 85 minutes. The steam canner would run dry.

The domed lid of most steam canners is tall enough to accommodate quart jars, as well as quarter-pint, half-pint or pint jars. The canner can be used fully loaded with jars, half-loaded, or with a single jar.

Directions

1. Place rack in bottom of canner, fill with water to the bottom of the rack. Preheat water.
2. Jars must be heated prior to filling. Keep hot jars hot, fill only with hot liquid and limit any cooling prior to processing. Follow headspace instructions on the recipes for boiling water canning.
3. Load canner with hot, filled jars and place dome lid on canner.
4. The steam canner must be vented prior to processing. Turn heat to high and watch for steam from the vent ports. Once a full and steady stream of steam (6 to 8 inches high) is seen coming from the vent, allow for one minute of venting before starting the processing time.
5. If necessary, adjust the heat throughout the processing time to maintain a steady stream of steam (6 to 8 inches) from the vent ports.
   1. Do not allow the canner to boil too vigorously or it will boil dry, creating an underprocessed and potentially unsafe product. Never open the lid during processing to add water.
   2. If the canner does boil dry, the food is underprocessed. You must begin again by refilling jars, wiping rims, using new lids and starting the processing over.
6. When processing time is completed, remove from heat and let stand for 5 minutes before removing the lid. When opening, tilt the lid away from you (this will avoid steam burns).
7. Use hot pads or a jar lifter to remove jars from canner. Cool jars on a rack or towel at room temperature, allowing air to circulate freely around them. Allow to cool at room temperature 12–24 hours.
   • Do not retighten screw bands after processing. Retightening of hot lids may cut through the gasket and cause seal failure.
8. Check that all jars have sealed, remove bands and clean outside of jars to remove any food residue.
9. Label with the date, contents of the jar and processing information.
10. Store jars in a cool, dark, and dry place. For best quality and nutritive value, use within one year.

SOURCES: Ingham, B. Guidelines for Using an Atmospheric Steam Canner for Home Food Preservation. University of Wisconsin Extension. 2011, revised 2021.

P. Willmore et al. 2015. Home Processing of Acid Foods in Atmospheric Steam and Boiling Water Canners. Food Protection Trends. 35:150-160.

Compiled by Caryn Wheeler, Jackson & Josephine County Extension, June 2019; Revised by Jared Hibbard-Swanson, Oregon State University, September 2022; Reviewed by Joy Waite-Cusic, Oregon State University, November 2022