To most people, canning appears to be the scariest and most complicated food preservation method. It requires specialized equipment, recipes, knowledge, and can even be dangerous if you don’t know what you’re doing. But before you panic and abandon the idea of canning altogether, keep reading. The basics of canning and how to do it safely aren’t as complicated as you might think.
1. The Difference Between Water Bath and Pressure Canning
The difference between canning methods is simple: Water bath canning works on a vacuum seal. Hot food is put into hot jars, which have the hot sterilized lids put on them. The rings are screwed down, and when the jar cools it forms a vacuum seal. This method, while very limited on equipment, only works on high acid and or high sugar foods which naturally resist bacterial contamination. However, the vacuum seal can randomly pop, making it risky for long-term storage.
Pressure canning has more equipment, more room for danger, but less room for bacterial contamination. The pressure canner puts the filled jars under a heat-based pressure, when the jars cool from the heat they seal. The high heat and pressure effectively kills bacteria, sterilizes the food, and gives a very strong seal. You can unseal a water-bath canned jar with your fingers, but you can’t do that with a pressure canned jar. Normally, unless food gets under the seal or the jar freezes, a pressure canned jar’s seal will not break.
2. The Parts of Your Pressure Canner
The pressure canner looks like a large aluminum, or stainless steel, pot. It has a lid that seals tight, with a small vent near the edge, and a larger spike-vent in the middle. The spike-vent is where the pressure weights will rest during canning, if using that type of canner. Newer canners often have a pressure gauge in the middle instead of a weight spike. Inside the pressure canner is usually a circular metal piece that keeps your jars from touching the actual bottom of the pot during canning.
3. Why You Should Check the Seal on Your Pressure Canner
The seal on your pressure canner is one of the most important things to check. If you have a faulty seal, your canner cannot build up enough pressure to safely preserve your food. Most pressure canning manufacturers have the option of buying replacement seals. Seals should be replaced every 3-4 years, whenever it begins to leak.
4. The Importance of Good Canning Jars
After you know your canner is in good repair, the next most important thing is your jars and lids. Only can with jars that are chip free, have solid non-chipped threads, and have no weaknesses in the glass. Chipped jars can be used for dried food storage, or fridge storage, never for pressure canning. Any jar with a chip or weakness could break under pressure, making a complete and utter mess (aka explode) in your pressure canner, potentially wreaking the seal on your other jars. If you have an exploded jar, discard both the jar and the food that was in it.
5. Canning Equipment You Need
Along with your canner and jars, have a good sturdy set of oven mitts. You will be handling hot, still-boiling-inside jars, so protecting your hands is essential. A jar lifter is also an exceptional tool for transferring hot jars out of the canner. Also useful is a lid lifter. This is used to lift sterilized lids out of the water they were sterilized in so they can be placed directly on the jar without contamination. A lid lifter can be created with a 4-6 inch piece of smooth wood, a rare earth magnet, and a screw to hold the magnet in an indent in the end of the wood.
6. Hot Jar Precautions
You’ve followed a canning recipe, the canner is no longer under pressure, and now you have to take the jars out. So, you clear the counter, take the lid off, and grab your jar lifter. STOP! First, place two or three tea-towel layers on your counter. Nothing is worse than taking a boiling hot jar and placing it on a cold counter. That is a recipe for shattered jars. Always put hot jars onto a layer, or two, of tea towels. Let cool completely on the towels.
7. Listen for the Pings and Always Check Seals
As the jars cool, they will seal. A seal sounds like a sharp pop, or ping, coming from the cooling jars. Once the jars are cool enough to touch, tap the top. If it is concave and there is no give in the lid, it is sealed. If it is convex and flexes when you push on it, it is not sealed and should not be stored. Jars that fail to seal can still be used, simply use them within the time-frame that food would require if it were freshly made.
8. Why Jars Fail to Seal
There are several reasons a jar may fail to seal. First, you may have used lids that had been used for canning once already. These lids will have been bent from being removed from the first jar, and will never seal safely again. To prevent this, always use new lids for canning.
Another reason may be because of food fragments on the rim of the jar, or that crept under the seal due to another jar shattering. You can only prevent the second by avoiding jars with visible chips or weaknesses. The first you can avoid by wiping down all jar rims and threads after filling, transferring the sterilized lids directly from the sterilization pot to the top of the jar, and using clean rings to immediately secure the lids in place.
A third reason for failure to seal is expansion. A jar with liquid contents under heat and pressure will expand, therefore the shoulders of the jar should be your fill-line. Never fill above the shoulders of the jar. This will insure you have head-room for content expansion, and will help insure you have consistently sealed jars. Over-expanded jar contents can get under the seal and prevent sealing.
9. Read Your Canning Guide
Most pressure canners will come with a guide for using their canner, as well as pressures and times for various fruits, vegetables, meats, and broths. Always follow the pressures and times listed in your canning guide. The only exception is if your guide is only for sea-level, and you are at a higher altitude. Higher altitudes often require higher pressure, or longer times than lower altitudes, particularly for meats, broths, and low-acid or low-sugar canning. (Here’s a list of pressure canner altitude adjustments). Remember, when canning a mix, the jar should be canned according to the rules for the longest canning and highest pressure food. In other words, if canning tomato sauces with onions and peppers, it should be canned according to the regulations for peppers, not tomatoes.