Your questions answered: steam canning

Back to Basics steam canner. Image courtesy BacktoBasics.

I have been answering many questions about the use of an atmospheric steam canner. The University of Wisconsin-Madison conducted research showing that an atmospheric Steam Canner may be used to safely can naturally acid foods such as peaches, pears, and apples, or acidified-foods such as salsa or pickles. The atmospheric steam canner uses only ~2 quarts of water (compared to 16 quarts, or more, in a boiling water canner) so you heat less water and processing can start more quickly.  Safe processing in a steam canner requires that all the following criteria are met:

  • Foods must be high in acid, with a pH of 4.6 or below. Foods may naturally be high in acid (most fruits) or have added acid.
  • An up-to-date, research-tested recipe is used. Approved recipes for boiling water canning may be safely adapted for use in a steam canner. Follow the instructions on an approved boiling water canning recipe for food preparation, jar size, etc. Once jars are filled and ready for processing, you’ll make the following adjustment-
    • At the processing step, place filled jars on the canner rack above hot/preheated water. Place the lid on the canner and heat, on high, until the canner vents. A full 6-8” column of steam will flow out of the vent holes in the canner. Once the canner continuously produces a full column of steam, this generally takes about 1 minute after steam appears, start timing. Process time is based on the time for a boiling water canner. Adjust heat, as needed to ensure the canner vents during the entire process time.
    • Processing time can be no more than 45 minutes. The processing time is limited by the amount of water in the canner base. The canner can not be opened during processing, and a vigorously boiling canner can boil dry within 20 minutes.
    • At the end of processing, carefully remove the canner lid and allow jars to cool on the countertop.
  • Make sure you remember to adjust processing time for elevation, just as you would for a boiling water canner, adding time as your elevation moves above 1,000 feet.

What about? ……

  • Can different types of appliances be used for steam canning? Even though newer appliances such as the InstaPot may have a steam setting, these appliances haven’t been tested for home canning (of any kind). Extension doesn’t recommend using any of the multicookers for home canning.
  • In our research we used a Back to Basics steam canner. This canner has a solid base and lid vents steam out the side and it’s easy to monitor heating. Can other pots be modified for use as a steam canner? Possibly.  Successful operation of a steam canner requires that jars sit above, not in, boiling water and that processing occurs in an atmosphere of pure steam. In order to achieve the pure steam needed, you have to get the air out of the canner. [Air is an insulator and air trapped in the canner may lower the processing temperature resulting in food that is unsafe or that will spoil.] At least one other type of steam canner has vent holes in the top of the lid and, properly vented, this model appears to work; check with a thermometer in the vent hole to make sure the temperature is ~212 degrees.
  • Can you ‘double stack’ jars in a steam canner? Whether using a boiling water canner or a steam canner, jars should not be stacked in the canner. Jars should sit on the rack in the canner surrounded by circulating, boiling water (boiling water canning), or surrounded by flowing steam (steam canning).

Happy preserving! Barb