Andrea Chesman: Steam Canners are Safe!

Research reveals it’s okay to add a steam canner to your home kitchen. Just make sure you preserve by the rules.

Boiling water bath canner (on left) and steam canner in Andrea Chesman’s kitchen. Photo courtesy of Andrea Chesman

I have a guilty secret. For years, I’ve been canning my high-acid foods (pickles, fruit, jams, and tomatoes) in a steam canner — even though the USDA has frowned upon the practice and even though I have taught classes using the boiling water bath canner. It was a “do as I say, not as I do” practice.

Finally (and too late to be included in my new book, The Backyard Homestead Book of Kitchen Know-How), researchers from the University of Wisconsin-Madison have concluded that steam canners — properly called “atmospheric steam canners” to distinguish them from pressure canners, which use pressurized steam — are safe and effective, when used correctly, for preserving acidified or naturally acidic foods.

Why do I prefer the steam canner to the boiling water bath canner?

The boiling water bath canner is a large pot with a lid and a rack to hold jars. Large canners hold up to 9 quart jars and small ones hold up to 7 quart jars. When using a boiling water bath canner, you have to bring at least 5 quarts of water up to a simmering temperature before adding your jars and waiting for the water to come to a boil. (Sometimes, adding even more water is required to keep jars submerged by at least 1 inch.)  This step alone can take 30 to 60 heat-filled minutes, depending on factors such as the size of your canner, whether the jars were hot-packed or raw-packed, and the BTU output of your stove — all this before you even begin processing.

By contrast, the steam canner is a 2-quart pot with a perforated metal rack for holding jars and a tall dome lid that allows a steady stream of steam to flow around the jars. There is less water to heat and thus, less time spent waiting. Best of all, pickles are exposed to less heat during steam canning, resulting in crisper pickles.

Adding citric acid to tomatoes can make them a candidate for steam canning. Photo courtesy of Andrea Chesman

The University of Wisconsin released guidelines for using steam canners and I am replicating them here, with my remarks in square brackets.

1. Only steam-can foods high in acid, with a pH of 4.6 or below. [This means pickles, fruit, jams and jellies, and acidified tomatoes, i.e., tomatoes to which you have added ½ teaspoon citric acid per quart.]
2. Always use a research-tested recipe developed for a water bath canner. Acquire recipes from university extension programs or from the NCHFP. The booklets that accompany steam canners usually don’t provide safe instructions.
3. Heat jars prior to filling them with food and minimize the amount of cooling time that passes prior to processing. You can use half-pint, pint, or quart jars. [I set the jars upside down on the canner rack and let them heat as I heat the water in the pot below. When the water has boiled for about 10 minutes, if I am not ready to can, I turn off the burner but leave the jars as they are. They will hold their heat.]
4. Process jars only after the temperature reaches pure steam at 212 degrees Fahrenheit. Wait to start the processing time until the canner has vented and a full, steady column of steam appears. Monitor the temperature with a thermometer. [The dome lid has holes to release the steam. This is why you can’t adapt another pot to be a steam canner. You need to see that steam escape.]
5. Modify processing time for elevation. In general, add 5 minutes for each 1,000 feet above sea level in elevation.
6. Only use recipes that require 45 minutes of processing time or less, as the amount of water in the canner may not last any longer. Don’t open the canner to refill the water while processing foods. [This is not a problem at most elevations. Most pickles and jams require 5 to 10 minutes of processing time. Acidified tomatoes and tomato purées require 40 minutes.]
7. Cool the jars in still, ambient air. Cool jars on a rack or towel away from drafts. Don’t place them in the refrigerator to hasten the process.

Prices for steam canners vary widely.  Go for the simplest, least expensive one you can find. My steam canner is about 35 years old and has been beaten up in suitcases when I take it to demos. It will last a lifetime. And remember: it is only good for high-acid foods, like the applesauce I am about to make.

It’s applesauce time!

Andrea Chesman is the author of many cookbooks, including The Pickled Pantry, Recipes from the Root Cellar, Serving Up the Harvest, Mom’s Best Crowd-Pleasers, and The Vegetarian Grill, which was nominated for a James Beard Foundation Book Award and won a National Barbecue Association Award of Excellence. She is a coauthor of 250 Treasured Country Desserts and The Classic Zucchini Cookbook, and her articles have appeared in the New York Times, Cooking Light, Food & Wine, Vegetarian Times, Organic Gardening, Fine Cooking, and other publications. Find more from Andrea on her website. Her newest book is The Backyard Homestead Book of Kitchen Know-How (Storey 2015).