Not everyone is aware that several years ago, the University of Wisconsin published research which indicates that a Steam Canner may be safely used for canning naturally acid foods such as peaches, pears, and apples, acidified-foods such as salsa or pickles,and jams and jellies 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 a steam canner can be used to safely preserve foods high in acid.
- A research tested recipe developed for a boiling water canner must be used in conjunction with the 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 steam canner can’t be relied on to provide safe canning instructions!
- Jars must be processed in pure steam at 210-212°F. Temperature should be monitored with a thermometer placed in the vent port. Steam has to flow freely from the canner vent(s) during the entire process, or the food is considered under-processed/unsafe. Some appliances come with a built-in temperature sensor in the dome lid which, in lab testing, appears to be accurate.
- Jars must be heated prior to filling and filled with hot liquid (for either raw or hot packed foods). Tested recipes approved for half-pint, pint, or quart jars may be followed.
- Processing time must be modified for elevation as required by a tested recipe.
- Processing time must be limited to 45 minutes or less, including any modification for elevation. The processing 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 210-212° 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.
For example, here’s how it works if you are canning strawberry jam: You prepare the fruit and boil with sugar and pectin as directed. Once the hot jam is filled into hot, sterile jars and the 2-piece lid applied (as directed), the jars are placed on the rack in the canner and covered with the dome lid. The heat is turned to high, and when you see a column of steam vent from the sides or top of the lid, check the temperature to make sure the canner is filled with steam (210-212°F). When temperature is reached, set a timer to the processing time indicated in your recipe. At the end of processing, turn off the heat and carefully remove the dome lid (Caution: it’s filled with steam). Use your jar lifter to remove jars and place on a towel or rack for cooling. And you are done. With much less water to heat than in a boiling water canner, I can guarantee that you will find this a quick and easy way to process acid foods – I sure do!
Print guidelines for using a steam canner are available. Safe preserving! Barb