Home-canning Using an Atmospheric Steam Canner

Atmospheric steam canning (ASC) is a research-tested method for effectively and safely preserving high acid foods (Willmore, Etzel, Andress, & Ingham, 2015). Steam canning is another way to preserve food at home and can be used in place of the standard boiling water bath method.

• Back to Categories
• Browse Guides
• PDF View

USUALLY, JARS ARE PROCESSED ON A FITTED RACK

within a shallow-base pan holding water and a high domed cover (see steam canner image), but dual-purpose steam and water bath canners can also be used. Steam canners have one or two vent holes on the cover. These cannot be used for pressure canning. Steam and water bath canners have similarities in the type of foods, safety requirements, and processing times, but need different amounts of water and preparation for processing. See table for easy comparison of the two methods.

Further Instructions for Use

Before using an ASC for home-canning, ask:

1. What food can be processed in an Atmospheric Steam Canner (ASC)?

ASC can only be used in canning acidic foods. High-acid foods (pH 4.6 or lower) include most fruits, jams/jellies, pickled products and some properly acidified tomato products. Low-acid foods are not safe to can in the ASC. For more information on high- versus low-acid foods, please read MSU Extension MontGuide “Home-canning Using Boiling Water Canners and Pressure Canners” (MT200905HR).

2. Do I need to follow a specific recipe or can I use a family recipe?

For safety, you must use up-to-date recipes that are research-tested and approved for home canning in a water bath canner. Research-tested recipes may be found in the USDA Complete Guide to Home Canning, on the National Center for Home Food Preservation website (http://nchfp.uga.edu/), or through your Extension office. We do not recommend using the manufacturer instruction booklet that comes with an ASC because recipes may not be research-tested. While many recipes passed down through family generations may taste good, they are not always tested for canning safety. Even if no one has gotten sick before, it is critical to use the recommended, up-to-date, research-based food preservation resources located in this publication. Save family or non-research approved recipes for immediate eating, refrigerating, or freezing!

Table 1: Atmospheric Steam Canner Compared to Water Bath Canner

Shallow base-pan with fitted wire rack. BY HOLLY MINER

Tested recipes approved for acidic foods in half-pint, pint, or quart jars may be processed in an ASC. BY HOLLY MINER

3. Why is it important to follow research-tested recipes and procedures when canning foods?

Canning preserves food from spoilage and destroys microorganisms that could cause foodborne illness. If foods are not canned correctly, they may look, smell, and taste safe, but could still cause illness or in some cases, death, when you, a family member, or a friend eats these foods. Researchers have tested many recipes with specific ingredients, processing times, and methods to make sure foods are canned safely and germ-free. Protect yourself and others when sharing home-canned foods by using research-tested recipes exactly.

4. Do I need to heat my jars?

Jars must be heated before filling for raw pack or heat packed methods and kept as hot as possible before starting the processing time in an ASC.

5. Do I need to adjust the recipe for altitude?

ASC must have adjustments for processing times, just like with water bath canning. Tested recipes must be used from reliable sources (see resource list), adjusting for elevation. Elevations can be checked at: http://www.daftlogic.com/sandbox-google-maps-find-altitude.htm or by typing, elevation (your town), in the search bar.

6. Will using an ASC reduce time spent processing?

The recipe stated processing time is the same for ASC and water bath methods. It takes less time to heat the water with ASC because there is less water. Tested recipes approved for half-pint, pint, or quart jars may be processed in an ASC. ASC should not be used if the water bath approved recipes require 45 minutes or more of processing time, including altitude adjustments.

7. When do I start to count processing time?

ASC processing time does not start until a 4–6 inch long, continuous flow of pure steam is coming out of the vent hole (~212°F at sea level). It is recommended to monitor the temperature with a dial-stem or digital thermometer placed in the vent port to make sure the steam stays at boiling temperature the entire processing time. Some ASCs come with a built-in temperature sensor in the lid, but these may not be accurate. The ASC must have steam the entire processing time to ensure food is not under-processed and potentially unsafe to eat. Because of the small amount of water used in ASC and evaporation, the recommendations are to only use water bath recipes that require 45 minutes or less, including any time adjustments for altitude. If processing steamflow or temperature is interrupted, we recommend freezing or refrigerate and eat within three days.

8. How do I cool the jars after processing time is completed?

After processing, remove the dome cover. When opening the cover, carefully tilt the lid so any steam escapes away from you. Jars should then be removed without tipping or tilting, and placed on a cooling rack or towels out of drafts and away from fans or vents. Do not cover jars and do not tighten ring bands. They should sit undisturbed at room temperature for 12 to 24 hours. The cooling time is part of the processing and is important for the overall safety of the finished product.

9. How do I know if a jar has sealed?

After cooling for 12–24 hours, remove the ring/screw band, and check the seal using one of three methods:

1.Press the middle of the lid, if the lid springs up on release, it is not sealed.

2. Tap the lid with the bottom of a spoon, if it makes a dull sound the lid is not sealed. A high-pitched, ringing sound indicates a correct seal.

3. Look across the lid at eye level, if the lid looks flat or bulging it is not sealed. A concave (curved down in the center) lid is correctly sealed.

If the jar did not seal, we recommend the food be refrigerated and used within three days or frozen.

10. How do I store canned food?

Properly canned foods can be stored in a cool, dark room. A furnace room or mechanical room is not a good storage location as temperatures change. If seals fail while the food is in storage, do not eat the food. If you are uncertain about a home canned food, follow the advice “when in doubt, throw it out.” Label and date jars, using the oldest canned items first. For best quality, use within one year.

Recommended Research-based Food Preservation Resources

• The National Center for Home Food Preservation (NCHFP) website is the most current source for publications, video clips, tutorials for the beginning home food preserver, frequently asked questions, and seasonal tips: http://nchfp.uga.edu/
• USDA Complete Guide to Home Canning, 2015. https://nchfp.uga.edu/publications/usda/INTRO_HomeCanrev0715.pdf.
• So Easy to Preserve, 6th edition, 2014. MSU Extension does not recommend earlier editions. http://www.soeasytopreserve.com
• Free Canning Timer & Checklist app: https://catalog.extension.oregonstate.edu/pnw689. This app will help to preserve foods using recommended processing times.

Additional MontGuides from Montana State University Extension

• Canning Pickles and Sauerkraut (MT200902HR)
• Home-Canning Meat, Poultry and Fish (MT200903HR)
• Making Jams, Jellies and Syrups including with wild Montana berries and fruit (MT200904HR)
• Home-canning Using Boiling Water Canners and Pressure Canners (MT 200905HR)
• Processing Fruit and Tomato Products in a Pressure Canner (MT200906HR)
• Drying Vegetables (MT200907HR)
• Freezing Vegetables (MT00908HR)
• Drying Fruits (MT200909HR)
• Freezing Fruits (MT200910HR)

Table 2: Altitude Adjustment for Water Bath and Atmospheric Steam Canner

*Increased time should also be included in 45 minute max processing time for ASC.

References

• Willmore, P., Etzel, M., Andress, E., & Ingham, B. (2015). Home processing of acid foods in atmospheric steam and boiling water canners. Food Protection Trends, 35(3), 150–160.
• Ingham, B. (2019). Safe preserving: Using an atmospheric steam canner. Retrieved from https://fyi.extension.wisc.edu/safepreserving/files/2019/04/SteamCannerGuidelinesFeb2019.pdf
• USDA. (2015). Complete Guide to Home Canning. Rev. National Center for Home Food Preservation (NCGFP) website, https://nchfp.uga.edu/publications/usda/INTRO_HomeCanrev0715.pdf.
• University of California Agriculture and Natural Resources. (2017). Guidelines for Safe Canning of Acid Foods in a Steam Canner. Retrieved from https://anrcatalog.ucanr.edu › pdf
• Based on the original document Guidelines for using a Steam Canner for Home Food Preservation, University of Wisconsin-Madison, 2019. Information reprinted with permission.

Acknowledgements

This MontGuide has been reviewed by Dr. Barbara Ingham, Professor, Food Science Extension Specialist with University of Wisconsin- Madison, Dr. Stephanie Smith, Assistant Professor, Food Safety Extension Specialist, Washington State University, Leigh Ann Bullington and Carla Due, University of Arkansas Extension Agents, and Emily Larkin and Shannlyn Spotted Elk, Montana State University Dietetic Interns.