Pressure Canning for Low-Acid Foods

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Pressure canning to preserve low-acid foods at home.

Vegetables, meats, poultry and seafood offer an opportunity to preserve low-acid foods for a well-balanced diet throughout the year. Low-acid foods are simple to preserve, yet require special handling to eliminate the risk of spoilage caused by botulism and its toxin-producing spores. To prevent this type of spoilage, low-acid foods must be heat processed at a temperature of 240°F for the established processing time in a tested fresh preserving recipe.

Pressure canning is the only way to fresh preserve at 240°F. Boiling water canners heat to only 212°F which is the temperature of boiling water. Because botulism spores do not grow in the presence of acid, high-acid foods may be safely processed in a boiling-water canner.

Low-acid foods include vegetables, soups, stews, stocks, meats, poultry and seafood. Recipes that combine high-acid foods, such as tomatoes, with low-acid foods, such as vegetables or meats, are still considered low-acid foods.

The directions below describe how to preserve meat, vegetables and other low-acid foods.

1. Equipment needed

A tested and reliable preserving recipe such as one found in the Ball Blue Book® Guide to Preserving or another reputable canning book.
Pressure canner for preserving low-acid foods; vegetables, meats and poultry.
Glass preserving jars, and bands with new lids.
Common kitchen utensils, such as wooden spoon, ladle and funnel.
Food to preserve: fresh vegetables, meat, poultry or seafood.

2. Other helpful utensils

Jar lifter
Lid lifter
Headspace gauge

3. Pressure Canning Directions

Thoroughly read the recipe and instructions. Be certain to understand the entire process before beginning. Assemble the equipment and ingredients. Follow the recipe guidelines for preparation, jar size, preserving method and processing time.

Check all jars, lids and bands for proper functioning. Jars with nicks, cracks, even rims or sharp edges may prevent sealing or cause jar breakage. The underside of lids should not have scratches or uneven or incomplete sealing compound as this may prevent sealing. Bands should fit on jars. Wash the canning jars, lids and bands in hot, soapy water. Rinse well. Dry the bands.

Heat the jars in hot water, not boiling, until ready for use. Fill a large saucepan or stockpot half-full with water. Place the jars in water; filling jars with water from the saucepan will prevent flotation. Bring to a simmer over medium heat. Keep jars hot until ready for use. Or, use a dishwasher to wash and heat jars. Keeping jars hot prevents them from breaking when hot food is added. Leave lids and bands at room temperature for easy handling.

To prepare for pressure canning, fill the pressure canner with 2 to 3 inches of water. Place the canner over medium-high heat. Bring the water to a simmer. Keep at a simmer until jars are filled and placed in canner. Follow manufacturer’s instructions for usage instructions.

Prepare the tested preserving recipe using fresh vegetables, meat, poultry, seafood or other quality ingredients.

Remove a hot jar from hot water, using a Jar Lifter, emptying water inside jar. Fill a jar one at a time with prepared food using a funnel leaving sufficient headspace as recommended in the recipe. Remove any air bubbles by sliding the a bubble remover or headspace tool between the jar and food to release any trapped air and ensure proper headspace during processing. Repeat around the inside of each jar 2 to 3 times.

Clean the jar rim and threads of the canning jar using a clean, damp cloth to remove any food residue. Center the lid on the jar for the sealing compound to come in contact with the jar rim. Apply the band and adjust until the fit is finger tight. Place the filled jars in the canner. The water level should be 2 to 3 inches above the jars.

Lock the pressure canner lid in place, leaving vent pipe open. Adjust heat to medium-high. Allow steam to escape through the vent pipe. Once there is a steady stream of steam escaping, vent for 10 minutes to ensure there is no air, only steam, left in canner. Close the vent using the weight. Gradually adjust the heat to achieve and maintain recommended pounds of pressure.

Process the canning jars at the recommended pounds pressure and processing time indicated in the recipe. Adjust for altitudes above 1,000 ft. Cool pressure canner by removing from heat. Do not remove the weighted gauge. Let canner stand undisturbed until pressure returns to zero naturally. Wait 10 minutes. Remove the weight and unlock the lid. Tilt the lid away from yourself. Wait 10 more minutes to allow jars to begin to cool.

Remove the jars from the pressure canner and set upright on a thick towel to prevent jar breakage. Leave jars undisturbed for 12 to 24 hours. Bands should not be retightened. This can interfere with the sealing process.

Check the lids for proper seal. Lids should not flex up and down when center is pressed. Remove the bands. Try to lift lids off with your fingertips. If the lid cannot be lifted off, the lid has a good seal. If a lid does not seal within 24 hours, the product should be immediately refrigerated. Clean the canning jars and lids. Label and store in a cool, dry, dark place up to 1 year.

Both Ball® and Kerr® have determined that preheating lids is no longer necessary. The current sealing compound for home canning performs equally well at room temperature as it does pre-heated in 180 F water. Simply wash the lids in hot, soapy water, dry, and set aside until needed.

Catherine’s Heirloom Tomato Pie

Quiche with tomato

A recent weekend brunch gathering brought out the Pioneer Dad family’s competitive spirit. There were dueling quiches and heated critiques from several family members. Entries included an onion bacon quiche, black forest ham and Swiss cheese quiche, a shallot mushroom version and a broccoli cheese offering of questionable heritage. But the hands-down winner and my favorite, from niece Catherine, was the heirloom tomato pie.

Here’s how she made it.

1. Ingredients

For the pie crust:

1-1/2 cups all-purpose flour
1/4 teaspoon fine salt
1 teaspoon sugar
1 stick cold unsalted butter, cut into 1/2-inch pieces
Or, one pre-made piecrust

For the pie filling:

3/4 cup shredded Manchego or pepper jack cheese
2 tablespoons extra-virgin olive oil
1 large onion, thinly sliced
2 1/4 pounds mixed heirloom tomatoes
Kosher salt
3/4 cup shredded mozzarella cheese
1/4 cup mayonnaise
3 tablespoons Panko breadcrumbs
3 tablespoons chopped fresh chives
3 tablespoons chopped fresh parsley
1 teaspoon chopped fresh thyme
Freshly ground pepper

2. Directions

Preheat the oven to 350 degrees F.


This piecrust recipe is sometimes called “3-2-1 dough” because it’s composed of 3 parts flour, 2 parts butter or fat, and 1 part water by weight. There is a bit of sugar for a slightly sweet crust.

Pie weights are needed to line the crust so that it doesn’t puff up while cooking. Dried beans work well for this. The dough can be made and baked up to 1 day ahead. Makes one 9 or 9-1/2 inch piecrust.

Add all of the dry ingredients and cut in the butter to combine, until it’s in pea-size pieces. Drizzle in 3 to 4 tablespoons of ice water and mix until the dough comes together. About 4 to 5 minutes. Add another teaspoon of ice water if the dough seems too dry. Shape the dough into a ball, wrap it up with plastic wrap, and refrigerate for 30 minutes.

Roll the dough out on a floured surface and transfer to a pie tin.

Blind bake the piecrust. Line the pie tin with foil and fill with dried beans. Bake until the edges are golden, about 20 minutes. Remove the foil and beans and continue baking until golden all over, 10 to 15 more minutes. Transfer to a wire rack and let cool.

Make the filling:

Heat 1-tablespoon olive oil in a large skillet over medium heat. Add the onion and cook, stirring, until golden, about 15 minutes. Let cool. Meanwhile, thinly slice the heirloom tomatoes; toss with 1-teaspoon kosher salt in a colander. Let the tomatoes drain, gently tossing occasionally for about 30 minutes.

Increase the oven temperature to 375 degrees F. Combine the Manchego cheese, mozzarella, mayonnaise, breadcrumbs, chives, parsley, thyme, kosher salt and pepper and the sautéed onion in a bowl. Spread evenly in the piecrust. Arrange the tomatoes on top. The pie looks best with a variety of yellow and red tomatoes of differing sizes. Drizzle with the remaining 1-tablespoon olive oil and season with pepper.

Bake until the tomatoes are lightly browned, about 50 minutes. Top the pie with the remaining 1-tablespoon each of fresh chives and parsley.

If the piecrust edges brown too early, wrap the edges with a strip of tinfoil before or during the final baking.


Storing Canned Food

There are finite limits to how long food can be preserved. Storing canned food faces several factors which limit the shelf-life over time. 1. Factors that limit shelf life Cans or jars with metal lids are susceptible to rust. If the rust becomes … [Continue reading]