Safe Preserving: Knowing Your Canner and Protecting Vegetables

Safe Preserving: Using an Atmospheric Steam Canner

Are you one of those persons that have to have the latest item and/or gadget that comes out on the market?  And, if you are, did you purchase an Atmospheric Steam Canner?  If so, you will want to save the following information as you use the canner during this canning season.

The University of Wisconsin has (finally!) published research which indicates that an Atmospheric Steam Canner may be safely used for canning naturally acid foods such as peaches, pears, and apples, or acidified-foods such as salsa or pickles, as long as all of the following criteria are met:

  • Foods must be high in acid, with a pH of 4.6 or below. Either a Boiling Water Canner or an Atmospheric Steam Canner can be used to safely preserve foods high in acid.

    Image courtesy of Back to Basics

    Image courtesy of Back to Basics

  • research tested recipe developed for a boiling water canner must be used in conjunction with the Atmospheric Steam Canner. Approved recipes can be found in Extension publications or from the National Center for Home Food Processing and Preservation. The booklet accompanying the Atmospheric Steam Canner can’t be relied on to provide safe canning instructions!
  • Jars must be processed in pure steam at 212°F. The canner must be vented prior to starting the processing time until a full column of steam appears. A full column of steam (6-8 inches) should be observed venting from the hole(s) in the side of the canner during the entire timed process. Ideally, temperature should be monitored with a thermometer placed in the vent port, but the placement of jars in the canner may make this difficult. Some appliances come with a built-in temperature sensor in the dome lid and these appear to be accurate.
  • Jars must be heated prior to filling, filled with hot liquid (raw or hot pack), and cooling must be minimized prior to processing. An Atmospheric Steam Canner may be used with recipes approved for half-pint, pint, or quart jars.
  • Processing time must be modified for elevation as required by a tested recipe. Elevation for any address can be checked here:
  • Processing time must be limited to 45 minutes or less, including any modification for elevation. Theprocessing time is limited by the amount of water in the canner base. When processing food, the canner should not be opened to add water. Regulate heat so that the canner maintains a temperature of 212° A canner that is boiling too vigorously can boil dry within 20 minutes. IF a canner boils dry, the food is considered under-processed and therefore potentially unsafe.
  • Cooling of jars must occur in still, ambient air. Cooling is important for safety. Jars should be cooled on a rack or towel away from drafts. Jars should not be placed in the refrigerator to hasten the cooling process.


Safe Preserving: Play it safe when preserving vegetables

The safety of the food that you preserve for your family and friends is important to you. The University of Wisconsin-Extension supports using up-to-date, research-tested recipes so that you know that the food that you preserve is both safe and high in quality. Here are a few quick tips on changes and substitutions that will keep your home preserved vegetables safe to eat.

Canning Vegetables. Vegetables are low in acid and must be canned in a pressure canner. There are some changes that you can safely make when canning vegetables at home.

  • You may create vegetable mixtures as long as there is a tested recipe for each vegetable that you are combining and you follow the processing time for the vegetable that has the longest time listed.
  • You may add a small amount of garlic (up to 1 clove per jar) to canned vegetables without impacting the processing time.
  • Do not thicken canned vegetables with flour or cornstarch, or add rice, pasta or other starchy ingredient, an unsafe product will result.

Research tested recipes for canning vegetables at home are available from the University of Wisconsin Extension at .

Homemade Preserves

Freezing Vegetables. Sometimes it’s just easier to freeze vegetables from the garden. Freezing vegetables takes minimal equipment, just a pot for boiling water or creating steam for blanching, and a bowl for cooling the blanched vegetables. You also need to make sure the frozen vegetables are well packaged for the freezer. In the heat of summer, freezing can be a ‘breeze.’  The key to freezing vegetables is quick cooling in ice water after blanching.  The cooling time should always equal the blanch time. So green peas blanched for 90 seconds are cooled for 90 seconds in ice water and then drained (well!) prior to packaging for the freezer.

Research tested recipes for freezing vegetables at home are available from the University of Wisconsin Extension at  The National Center for Home Food Preservation also has some ideas for quickly converting your garden produce into frozen food for later enjoyment,

Drying Vegetables. Most vegetables dry even more successfully than fruits. For tips on making dried vegetables, including vegetable leathers, check out information from the National Center for Home Food Preservation at

Safe preserving!