The Pressure is On: Preserving your Backcountry Bounty
by Becca Moffat, Rokslide Prostaff
For those of us fortunate enough to bring home an abundance of game meat and fish, full freezers are a good problem to have. Yet several summers ago when we were unexpectedly lucky dip-netting salmon, I found myself with nearly one hundred freshly caught fish and little room in our three freezers.
I was faced with a choice: go out and buy a fourth freezer we really didn’t have space for, or learn to use the pressure canner I had been avoiding since I purchased it. The pressure canning option won out. We ended up with six cases of delicious canned salmon, safely preserved without fridge or freezer and ready to eat at a moments notice.
Though intimidating at first, pressure canning is an easy and safe alternative for preserving meat, fish, and other low-acid foods that you can’t safely can using a water bath canner (more on that later). Canning works by raising the contents of jars or cans to a temperature that kills the spoiling bacteria, yeast, mold, or enzymes present in all foods. Canning then utilizes the change in pressure that occurs during cooling to seal the lid in place preventing any spoiling agent to enter the newly sterilized environment.
Research has shown that hazardous enzymes, yeast and molds are destroyed at temperatures less than 212° F, the boling point of water (except at high elevation). Bacteria, however, are harder to kill. The bacteria Clostridium botulinus produces the poison commonly known as botulism, and can survive temperatures up to 225° F. To ensure all bacteria has been eradicated, food needs to be processed at 240°-250 F, a temperature only achievable by heating the contents under pressure. Because the pressure inside the canner is altered by high altitudes, know the elevation where you are canning and follow the pressure guidelines given by your recipe.
Many of us are familiar with preserving tomatoes, jam, and other products in boiling water or “water bath” canners. Water bath canning is only safe for foods considered “high acid” with a ph of 4.6 or lower, because bacteria cannot survive under acidic conditions. Because game meat, fish and, many vegetables are low acid foods that support the growth of bacteria, they can only be safely canned using a pressure canner.
Even with a pressure canner, foods of different densities take longer to reach the necessary safe temperature. Fortunately, extensive research has been conducted on canning and food safety over the last several decades and many tested recipes with safe processing pressures and times are now available for many foods (see Canning Resources below). Although I love to experiment when I am cooking, pressure canning is the one arena where I don’t deviate from approved recipes. Family and friends sometimes tease me about being obsessed with recipes and instructions, but it’s truly the only way to ensure my home canned goods are safe to eat!
The following are general instructions for pressure canning with glass jars. Food can also be canned in a similar manner into metal cans, but the procedure varies a little bit. Please refer to the specific instruction manual for your pressure canner. I also recommend picking up a canning accessory kit, as handy tools like a lid lifter, canning funnel, and jar lifter really make the process easier. I also depend heavily on a kitchen timer.
Step 1: Prepare jars, rings and lids
Jars and rings should be freshly washed. Jars need to be inspected to ensure they are free of cracks or other blemishes. The clean rings can be set aside, while the jars should be keep kept hot by either keeping them in boiling water, or in the dishwasher (without soap) on the sterilize setting until just before you are ready to use them. Also, prepare lids by placing them in a pan of simmering water (do not boil). The lid seals really only need to be simmered for three minutes before use, so you can delay this step if needed.
Step 2: Fill the jars
Depending on what you are preserving, the food that you will be placing into your jars will either be cold or preheated. Although the canning process continues to cook the product being canned, many recipes like soup or chili call for mixing all the ingredients and bringing them to a simmer before putting them hot in the jars (“hot packing”). Other foods like meat, fish and some vegetables can be placed into jars cold/raw for cooking during the canning process (“cold packing”).
Regardless of whether you are hot packing or cold packing, a canning funnel will make it easier to fill the jars without making a mess. Be sure to leave the correct amount of space at the top of each jar. Known as “head space,” this is crucial to keeping your jars from overflowing during the canning process, which might cause failure of the lids to seal.
Step 3: Clean and place lids
Once your jars are filled, wipe the tops carefully to make sure nothing remains that could interfere with sealing. Then take a lid from the hot water (a magnetic lid lifter will keep you from burning your fingers) and place it on top of each jar. Screw a ring on to hold each lid in place, tightening it until you meet resistance.
Step 4: Prepare the canner and place jars inside
Prepare the canner by placing it on the heat source, and adding water according to the manufacturers instructions. There should be a rack or grate in the bottom to keep the jars from touching the metal. Place the prepared jars inside the canner on the rack, rearranging them so they fit. Depending on the model of canner and size of jars you are using, you may end up stacking more than one layer of jars with a rack in between.
Step 5: Affix the canner lid, turn on the heat, and exhaust
Once your jars are inside, put the lid on the canner and tighten it down according to the manufacturer’s instructions. With a weighted canner, make sure the weight is not on top of the vent in the lid, but keep it someplace nearby (if you are using a canner with a stopcock on top, make sure it is open).
Start the heat under the canner. As the contents inside start to get hot, the water you poured inside will start to boil and eventually appear as steam from the lid vent (exhausting). Exhausting ensures there is no air left inside the canner or the jars that might interfere with even temperature distribution. Most manufacturers instruct you to exhaust your canner for a full 10 minutes but follow your instruction manual.
Step 6: Bring your canner to pressure and process your jars
Once you have exhausted the canner, place the weight on top of the vent (or flip your stopcock) being sure to use the correct amount of weight outlined in your recipe. If you have a pressure gauge on your canner, you will notice the internal pressure starting to rise almost immediately. Once the internal pressure reaches the target, the weight will start to jiggle. Your processing time starts now. During the processing, your only task is to keep an eye on things and make sure the correct amount of pressure is maintained. Correct pressure is achieved when the weight jiggles a few times each minute, but NOT constantly. You might need to adjust the heat source so that the pressure is maintained.
Step 7: Allow pressure to reduce and open canner
Once the canner has processed for the correct amount of time, turn off the heat and let the pressure inside the canner gradually reduce on its own. Once the external pressure gauge reads zero, the weight can be removed (or stopcock opened) and the lid safely opened. Be careful to open the lid away from you as the contents inside are really hot and a lot of steam will come out.
Step 8. Remove jars for cooling
Use your jar lifter to remove each of the jars individually, placing them in an area free of drafts to cool. I usually place a bath towel on a table or countertop for protection and cool my jars there. You may notice the contents of the jars boiling for several hours after you remove them from the canner. You may also hear a popping sound as the lids “suck down” to the tops of the jars as they cool. Allow the jars to sit undisturbed for 24 hours to cool completely. Then check all your lids to ensure that they sealed. Lids should be sucked down tight to the top of the jars, and shouldn’t flex if you push on them. If any of your lids failed, the jars can be reprocessed all over, or placed in the fridge and consumed within the next week.
Rings should be removed for long term storage. If you keep canned jars away from heat and light, they should have a shelf life of at least a few years. Lids should be difficult to remove when seals are intact. Never eat anything from a jar with a lid that flexes, or where discoloration or gas bubbles are evident. If in doubt about the safety of any canned food product, throw it out!
Canning Resources
National Center for Home Food Preservation
University of Wisconsin Dept. of Food Safety and Health
“Preservation Using a Pressure Canner“
Presto Industries
“FAQ and General Information About Pressure Canning“
USDA List of Cooperative Extension Service Offices by State (Each state has an individual site, and these are great resources for recipes and other information)
“USDA“
Becca Moffat, residing in Wasilla Alaska, loves to hunt, cook, and write.
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