What is
pressure canning?
Pressure canning is the best method for safely preserving food. 'Safely' means that all harmful bacteria are killed during the canning process—including the botulism bacterium. Because pressure canning kills these harmful bacteria, the food you preserve this way can be stored for at least a year—right on the shelf, without needing a freezer.
Pressure canning is done with a special pot called a pressure canner. A pressure canner looks like a pressure cooker, but there is one important difference: with a pressure canner, you can see on the pressure gauge exactly how much pressure has built up inside. This information is essential for preserving food safely.
If you want to preserve low-acid foods like vegetables, meat, and fish, pressure canning is the only safe method.
How does
pressure
canning work?
Place the jars with the food you want to preserve on a special rack inside the pressure canner. Then fill the canner with 3 liters of water. Since a pressure canner works with steam, the jars do not need to be mostly submerged in water like in traditional water bath canning.
Next, you close the canner. The canner comes with a pressure weight, which is used to seal the steam vent. At the start, you do not place the weight on the steam vent yet.
Place the canner on the stove and turn the heat to the highest setting. As the canner heats up, steam fills the inside and pushes out all the air. Once the water starts boiling, steam will begin to escape from the vent.
After 10 minutes, the canner is evenly filled with steam. That’s when you place the pressure weight on the vent. Now the pressure inside the canner begins to rise, and the temperature increases to over 115 degrees Celsius. That high temperature is necessary to kill all bacteria.
Once the processing time appropriate for the type of food you’re canning has passed, you remove the canner from the stove. As it cools down, the jars automatically create a vacuum.
Here’s how that works: during heating, the contents of the jar expand, pushing out all the oxygen. As the jar cools, the contents contract, pulling the lid downward and creating a vacuum seal. This makes the jar airtight and keeps your preserved food shelf-stable.
Botulism and
preserving
What is botulism and why is it dangerous?
When is there a risk of botulism?
Of all the harmful bacteria out there, the botulism bacterium is most often mentioned in connection with food and for good reason. Botulism is a serious, potentially life-threatening illness caused by the charmingly named bacterium Clostridium botulinum. Botulism can cause paralysis and even lead to death. The most well-known form is foodborne botulism.
This occurs when food becomes contaminated with the bacterium and is then not preserved safely. Improperly preserved food can create the perfect environment for the bacterium to thrive.
The bacterium that causes botulism is, in itself, not dangerous to humans or animals. After all, it’s found everywhere in soil and water. Under normal circumstances, this poses no threat.
The danger arises when the right conditions allow the bacterium to produce toxins. These toxins can cause paralysis and, in severe cases, be fatal.
The botulism bacterium thrives best in conditions with little oxygen, moisture, and low acidity in other words, exactly the conditions found in a vacuum-sealed jar of, for example, vegetables.
With pressure canning, you cook under pressure. This allows the temperature to get high enough to kill all bacteria. So, if you've preserved a jar of beets in your pressure canner and you open it a year later, you can use it straight away for example, in a salad. There’s no need to boil it again before eating it safely.
That’s different from traditional water bath canning. If you open a jar of vegetables after a year that was preserved this way, you must boil the contents for at least 10 minutes to neutralize any potential toxins.
And even then, you haven't necessarily killed all the bacteria.
Pressure: the manometer and the pressure weight
When the lid is on the pressure canner, the canner is completely sealed. As the water begins to boil, the canner fills with steam. This increases the pressure inside the canner, which in turn raises the temperature to above 115 degrees Celsius. At that temperature, all bacteria are killed. The amount of pressure needed for safe pressure canning depends somewhat on your altitude.
To reach the correct temperature inside your pressure canner, you need to take into account your elevation above sea level. That’s because water boils at a lower temperature at higher altitudes. A lower boiling temperature is not effective enough to kill most bacteria.
Below 300 meters
The minimum pressure needed for safe canning when using a weighted gauge is 10 PSI. If you’re using a canner with only a pressure gauge, it’s recommended to use 11 PSI.
The CanMate has both options, so you can safely preserve food at 10 PSI.
Above 300 meters
If you live at an elevation higher than 300 meters, it’s important to adjust the pressure according to your altitude. Below is a table showing which pressure to use. For example, if you live at 800 meters, you should bring the pressure up to 15 PSI when using a weighted gauge, and to 12 PSI when using a pressure gauge.
The CanMate is equipped with a weight of 10 PSI and of 15 PSI, so you can safely preserve food at any height.
Pressure
Canners with a Pressure Weight and/or Pressure Gauge
There are two types of pressure canners:
-
Canners with only a pressure weight (weighted gauge)
-
Canners with both a pressure weight and a pressure gauge (dial gauge)
A canner that uses only a pressure weight operates with a weight on the vent. This weight begins to rock or jiggle when the correct pressure is reached. For example, if your canner has a 10 PSI weight, it will start rocking and hissing at 10 PSI. If it’s a 15 PSI weight, it will do so at 15 PSI.
The altitude where you live determines which weight you should use. Once the weight starts to rock and hiss, you know your pressure canner has reached the correct pressure and you can start timing.
Our CanMate has not only two weights but also a pressure gauge (dial gauge) that shows you exactly what pressure is building up inside the canner. This makes it easy to see when the right pressure is reached. It’s important to have the pressure gauge calibrated once a year to ensure it stays accurate. This can be done by specialized companies, and you can easily find one near you with a quick Google search.
So our CanMate Pressure Canner 22 qt is equipped with both a pressure gauge and a pressure weight. The latest version comes with both a 10 PSI and a 15 PSI weight.
The advantage of having a pressure weight is that it makes yearly calibration of the pressure gauge unnecessary. You simply wait until the weight starts hissing and rocking—that’s your signal that the canner is at the correct pressure. Another benefit of the weight is that you can hear it, even from a distance, so you don’t need to keep checking the gauge visually.
Getting started
When starting with pressure canning, first choose your recipe. You can work with USDA-tested recipes. The USDA is the United States Department of Agriculture, which also focuses on food safety. Here is the link to their recipes:
Of course, in English, and they work with American sizes.
We provide the perfect alternative with European measurements. Our pressure-canning recepy book is offered in different languages and features recipes calibrated to grams and liters. Get your copy here!
01
After choosing your recipe, you can begin. Make sure your jars are clean. Sterilization is not necessary because it takes place during pressure canning.
Cleaning your jars
02
Fill the jars
Prepare your jars for filling. It’s most convenient to use a funnel with a wide opening to keep the rims clean.
Leave the headspace specified in your recipe on average, about 2.5 cm at the top of the jar.
03
Then stir the jar with a chopstick. This helps to remove any air bubbles. It's important to remove as many air bubbles as possible, as air can cause your product to spoil over time.
That’s why we aim to eliminate as many bubbles as we can. During the pressure canning process, the rest of the air will naturally be pushed out of the jar.
Remove air bubbles
04
Screw the lid on.
Next, thoroughly clean the rims of your jars. If you’ve used a good funnel, you’ll hardly need to clean them. For non-greasy or non-sticky foods, a clean dishcloth dampened with water is usually enough.
For greasier or stickier foods, vinegar works well to degrease the rim just dampen a clean cloth with vinegar and wipe around the edge.
It’s crucial that the rim is completely clean, otherwise the lid won’t seal properly. Screw the lid on finger-tight—don’t over-tighten.
If you crank it down too hard, any remaining air won’t be able to escape during pressure canning, leaving air trapped in the jar, which you want to avoid.”
05
Once your jars are ready for canning, fill the pressure canner with 3 liters of water. It doesn’t matter how many jars are inside the canner, you always use 3 liters of water.
Note: if your jars are hot, add hot water; if they’re cold, add cold water. Then place the jars into the canner.
Check carefully that the lid’s sealing ring is properly seated, then put the lid on the canner. Turn the heat to high and wait until you see steam escaping from the valve. The time this takes will vary depending on your stovetop and whether you started with hot or cold jars.
Once steam is flowing (and on the CanMate you’ll see the right‐hand handle pin lift), lower the heat slightly. You need to avoid losing too much moisture from the canner, or it could run dry.
Fill your canner
06
Steam for 10 minutes and place the weight
Then set your timer for 10 minutes. During those 10 minutes, the canner will fill completely with steam, pushing out the air.
After 10 minutes, you can place your weight on the valve, allowing the pressure to build slowly.
07
If you’re using a canner with a pressure gauge, keep a close eye on it until it registers your target pressure. If you’re using a weighted-gauge canner, wait for the weight to start rocking.
Once the correct pressure is reached, start your timer for the recommended processing time that should be specified in your recipe. Remember: only start the timer after you’ve hit the correct pressure.
Building pressure
08
Cool and empty
Once your timer goes off, remove your canner from the stove and allow the pressure to fully release. If your canner has a pressure gauge, you’ll be able to see when it drops to zero. If you’re using a weighted-gauge canner, the pressure has released when you no longer hear any hissing.
Now you can remove the weight. Wait another 10 minutes before opening the lid. After that, wait another 10 minutes, then carefully remove the jars from the canner using the jar lifter.
You want to cool the jars slowly to avoid exposing them to a sudden temperature shift. The contents of the jars are still very hot, and when heated, they expand. If the surrounding environment is much cooler because you quickly remove the jars from the canner, the hot contents might force their way out. This can cause liquid loss and may allow air to enter between the glass and the lid, preventing a proper vacuum seal.
So, allow your canner to cool down gradually, and wait 10 minutes between each step to avoid rapid cooling.
Even with the most careful handling, you may lose some of the liquid from the jars. As long as more than two-thirds of the liquid remain in the jar and the jar is vacuum-sealed, you can still store it in your pantry.
If you lose more than that, it’s important to refrigerate the jar after cooling and consume it first, even if the vacuum seal is intact.
09
Then, allow your jars to cool down for 24 hours and check if they have properly sealed. If you're using mason jars, remove the ring and check if the lid stays securely in place. You can lift the jar by the lid, and if it stays on, the vacuum seal is strong enough.
If you're using reusable screw-top jars, check if the lid has been sucked inward and doesn't make any noise when you press it.
If you're using Weck jars, check if the lid stays in place when you lift it by the lid without the clamps.
If the vacuum test is successful, your jar can go to the pantry.
It is recommended to consume the contents within a year.
Pantry
Pressure canning
cooking times
( in minutes)
Vegetables
-
Potatoes – pre-cook for 10 min.
-
Asparagus
-
Beets – pre-cook for 15–25 min.
-
Beans in tomato sauce
-
Mushrooms
-
Green peas
-
Dried beans – soak for 12–18 hrs
-
Corn kernels
-
Okra
-
Peppers & bell peppers
-
Pumpkin (cubed)
-
Green beans
-
Spinach
-
Carrots
-
Sweet potatoes
Meat, fish & meals
-
Ground meat & meat chunks
-
Chicken or rabbit with bones
-
Chicken or rabbit boneless
-
Smoked fish
-
Fish
-
Meat broth
-
Chili con carne
-
Vegetable soup
-
Vegetable soup with meat
-
Soup with fish & shellfish
-
Spaghetti sauce with meat
-
Spaghetti sauce without meat
Pints
+/- 500ml
Quarts
+/- 1 Liter
35
30
30
65
half pint 45
40
75
55
25
half pint 35
55
20
70
25
65
40
40
35
75
Pint 45
40
90
85
40
Pint 35
90
25
90
30
90
Pints
+/- 500ml
Quarts
+/- 1 Liter
90
75
90
x
160
25
90
75
75
100
70
25
75
65
75
110
100
20
75
60
60
100
60
20