Pressure Canning

I wish I hadn’t waited so long to start pressure canning. This method uses steam pressure to create high heat and is used to preserve low-acid foods such as beans, broth, fish, meat, and most vegetables that have not been pickled. Having a pressure canner has allowed me to greatly expand my canning repertoire.

For years I was intimidated by the idea of boiling-hot steam pressure building up inside a locked-down pot, and by the insistent rattling of the weighted gauge. My mother never used a pressure canner but she did have a pressure cooker, which she used occasionally to cook potatoes quickly. The gauge would hiss and rattle maniacally, and my mother would hiss and rattle back in Italian. I steered clear.

It was my friend Cathy Barrow who convinced me to take the pressure-canning plunge. In her book, Mrs. Wheelbarrow’s Practical Pantry, she gives a convincing argument for pressure canning: reducing dependency on commercially processed foods. Two of the foods she pressure-cans are beans and broth. Since I use both of these regularly in my Italian kitchen, I decided it was time to dive in.

Pressure canning works by heating jars of food to 240°F for a prescribed amount of time through the buildup of steam pressure. It is the only safe method for preserving low-acid foods (foods with a pH level of 4.6 or higher) for long-term storage, including vegetables that have not been acidified with vinegar, lemon juice, or citric acid.

Clostridium botulinum, the bacteria that causes botulism, resides on most foods. In the open air, the bacteria are harmless; they only thrive in moist, low-acid, oxygen-free environments—in other words, places like a sealed jar. Processing low-acid foods in a boiling-water bath is not enough to kill the deadly toxin. But bringing them to 240°F in a pressure canner destroys any botulism spores that may be lurking, making food completely safe to eat.

A pressure canner is an expensive and bulky piece of equipment; buy one only if you are committed to using it. In this book, a pressure canner is employed to can Bottled Beans in Tomato Sauce (page 124) and Homemade Meat Broth (page 126). But beyond those recipes, you can use a pressure canner to safely can most vegetables and fruits, as well as meat, poultry, and fish.

You can also use it to can tomatoes. Although we think of tomatoes as acidic, their acidity is variable, hovering right around 4.5 pH. Tomatoes can be safely canned in a water bath as long as acid (usually in the form of lemon juice or citric acid) is added. If you use a pressure canner, there is no need to add the extra acid.

While it is safe to can some meat sauces in a pressure canner, I don’t do it. I prefer thick meat sauces, and I just can’t be sure that the heat from the pressure-canning process penetrates through to the center of the jar. For that reason, I freeze meat sauces.

Certain foods cannot be safely canned, even in a pressure canner. These include dairy and egg products; dense foods, such as mashed potatoes or pumpkin; and pasta, grains, and products made with flour. Then there are the foods that literally turn to mush under the extreme heat: broccoli, cauliflower, and zucchini and other summer squashes. As always when it comes to canning, be sure to follow the recipe closely and refer to the manufacturer’s instructions and guidelines before proceeding.

Pressure canners. All American and Presto are two leading manufacturers of pressure canners in the United States. Canners range in price from about $70 to $350 and in size from 10 quarts to 40 quarts, the latter of which can hold up to 32 pint jars or 19 quarts (!) at one time. I use an All American 21-quart pressure canner that can hold up to 19 pint jars or 7 quart jars. It is plenty big for my needs.

Pressure canners come with lids that lock on tightly. Some models have lids with rubber gaskets and handles that clamp down; others are beveled along the rim to fit the top of the pot and are secured with bolts and wing nuts that screw the lid down. A pressure canner lid is outfitted with several pieces, depending on the make and model: a weighted gauge or a dial gauge to regulate and monitor pressure; a steam vent or pipe; and a safety lock or plug to ensure that the canner is sufficiently depressurized before you can open it.

Most pressure canners also come with a perforated rack; some have two so you can stack the jars. You will also need clean jars, lids and rings, and the other tools listed in the section on water-bath canning (page 15).

Basic instructions for canning with a pressure canner

Before you start, read the instruction booklet that comes with your pressure canner and follow the directions to the letter to properly set up and use the canner.

1 • Start with clean equipment. Make sure your canner and canning tools have been washed in hot soapy water and thoroughly dried. Spread a clean kitchen towel out on the work surface near the canner; this is where you will set the jars after they have been processed.

2 • Set up your canner. Set the rack in the bottom of the pot and add 2 to 3 inches of water. There is no need to fill the pot; you just need enough to create the steam pressure that will raise the temperature inside to 240°F. Add a splash of distilled white vinegar to the water to help keep the jars shiny.

3 • Thoroughly wash and dry your jars, rings, and lids. There is no need to sterilize jars destined for pressure canning. The extreme heat will sterilize them during processing.

4 • Fill the jars with the food you are canning. Fit the jars with the wide-mouth funnel and ladle or pack in the food, taking care to leave the amount of headspace—the space between the top of the food and the top of the jar—specified in the recipe. Leaving too much space could prevent the lid from sealing properly; too little might cause food to seep out and also prevent a seal. Gently run a bubble remover or a plastic chopstick around the inside of the jar, moving it up and down, to dislodge any air bubbles.

5 • Carefully wipe the rims of the filled jars clean with a damp paper towel. If there is oily residue on the rim, dip the paper towel in distilled white vinegar; an oily surface may prevent jars from sealing properly.

6 • Set the jars in the canner on top of the rack. Do not set them directly on the floor of the canner. Secure the lid on the canner, following the manufacturer’s instructions, so that it is properly locked. My model, for example, requires a light oiling of the beveled surface of the rim of the pot. The lid is then placed on the pot, lined up, and locked into place, and the bolts and wing nuts tightened.

7 • Place the canner over high heat and let it heat up until steam begins to escape from the steam vent or pipe; the steam will be intermittent at first, then rise in a steady column. Once the column of steam is escaping at a steady stream (you should be able to see and hear it), set a timer and let the steam vent for 10 minutes. Then place the gauge onto the vent, making sure you choose the pressure setting called for in the recipe. For example, the recipe for Bottled Beans in Tomato Sauce (page 124) calls for processing the jars at 10 pounds of pressure. Choose the hole in the gauge marked “10” and slide it over the vent pipe. (If you are processing at an altitude higher than sea level, you will need to adjust the pressure and the processing time; see the paragraph at the end of these instructions.)

8 • If you are using a dial gauge, monitor the dial and begin timing the canning process when it reaches the correct pressure (bottled beans, for example, need to process for 75 minutes from the time the gauge indicates the canner has reached 10 pounds of pressure). Adjust the heat as necessary to keep the pressure at the correct level. If you are using a weighted gauge, listen for the first rattle indicating the pot has reached the correct pressure. Once that happens, start timing the canning process and keep listening. You want the gauge to jiggle one to four times per minute. If it is rattling constantly, you need to lower the heat; if it is barely rattling at all, you need to raise it. Over time, you will get a feel for how high or low you need to maintain the heat on your burner to maintain the proper pressure.

9 • Once the food is done processing, turn off the heat and let the canner cool gradually until the pressure dial gauge has dropped to zero (this can take 30 minutes or longer). Once the dial is at zero, use a pot holder to remove the weighted gauge. Wait 2 minutes before loosening the wing nuts or unlocking the lid. Remove the cover by lifting the edge away from you to protect your face from steam. Remove the jars with a jar lifter and set them on a clean kitchen towel. Their contents will be bubbling. Let the jars rest and cool completely before testing the seal on the lid. To test, press your finger into the center of the lid; it should remain concave and not spring back up. Lift the jar by the edge of the lid. If the lid stays on, you have a good seal. If a jar has not sealed properly, remove the lid and carefully wipe the rim of the jar. Replace the lid with a new one and screw on the ring. Reprocess any improperly sealed jars within 24 hours, or store them in the refrigerator and use within a week.

10 • Inspect your pressure-canning equipment regularly for chips, cracks, rust, and general wear. The dial gauge, which displays the amount of pressure in the canner, needs to be tested for accuracy every year. A hardware store or your local county Cooperative Extension office should be able to offer this service. To determine the proper pressure and processing time for higher altitudes, refer to the manual that comes with your canner.

For more information, including how to adjust these instructions for high altitude, visit the National Center for Home Food Preservation (www.nchfp.uga.edu), All American Canner (www.allamericancanner.com), and Ball Corporation (www.freshpreserving.com).