Atmospheric steam canning – A new option

 

Food Safety Feature Articles

 

Atmospheric steam canning – A new option

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:

 

• Jars must be in pure steam so the canner must be vented until
  a full column of steam (8-10 inches) is released from the vent ports.
  The internal temperature must remain at 212 degrees Fahrenheit or
  higher throughout the processing time. Some steam canners have a
  thermometer built in. For those that do not, a thermometer can be
  inserted into one vent port to monitor the temperature.


• Processing time, including any added for higher elevation, must
  not exceed a total of 45 minutes. This is because the water in the
  base evaporates as the process continues. Do not let the canner boil
  dry — this may result in an unsafe product. Never open the canner
  to add liquid during the process either. According to University
  of Wisconsin Extension, “A canner boiling too vigorously can boil
  dry within 20 minutes.”

 

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.

Last update:
Monday, August 01, 2016