How to (Safely) Can Foods
Posted by Grange Co-op on 9th May 2023
Nothing is more satisfying than canning food that you’ve grown and lining up the canning jars in the pantry. Preserving food might be a family tradition that you watched your parents or grandparents do when you were a kid. People have been canning food in jars since the early 1800s. Unfortunately, poorly designed pressure cookers and improper canning practices led to serious illnesses and injuries. Today, canning is a lot safer — if you take a few simple precautions.
Pressure Canning Low Acid Foods
There are other methods of food preservation, but not for low-acid foods. These are things like red meat, poultry, milk, and most vegetables which have a pH value above 4.6. These foods must be preserved using a temperature of 240ºF throughout the process. Failing to maintain the 240ºF temperature allows the bacteria Clostridium botulinum from the soil to survive the canning process. This bacterium causes botulism, the deadliest type of food poisoning. C botulinum doesn’t grow in highly acidic foods, making it unnecessary to preserve some foods using the same high temperature.
Instant Pot Canning
Instant pots are great appliances when you want to cook food in record time. People often wonder if their ability to cook quickly makes them good for canning foods too. The problem is that they don’t hold a consistent temperature. They fluctuate between 239ºF and 242ºF, dropping below the required 240ºF temperature required for low-acid foods.
While you should never attempt to can low-acid foods in an instant pot, you can use it to preserve some high-acid foods. These foods have a pH of 4.6 or lower and include jellies and jams, pickles, and sauerkraut. A temperature of 140ºF should be enough to ward off any yeast or mold spoilage. Just make sure that your instant pot has the capacity to preserve these types of food. Many smaller instant pots can’t accommodate the smallest size of canning jars.
Water Bath Canning
This is another food preservation method that is safe for high-acid foods. It requires a water bath cooker and should reach temperatures of 212ºF. Since water bath canners are designed for this purpose, they might provide the simplest and safest method of preserving high-acid foods.
How Pressure Cookers Have Changed Through the Years
Early pressure cookers relied on gaskets to form a secure seal and a valve that prevented too much pressure from building up inside. Early models were poorly constructed. The valve would get clogged, allowing pressure to build up inside the cooker. The gasket would blow off, allowing steam and boiling hot water to spew out.
Modern pressure cookers have safety features that make them less dangerous. Some cookers still have gaskets, but they won’t build pressure if there is a leak. If you’re tempted to try out a vintage cooker that was handed down through the family, don’t! Save it for making jams and jellies, or other foods that don’t require pressure.
While today’s pressure cookers are much safer than those of the past, it doesn’t mean using them is foolproof. You still need to use the right type of cooker, stove, containers, and process to safely can different types of food.
Keep in mind that the best cookers today only last about five years. To ensure safety, start canning with a new cooker and follow the directions provided by the manufacturer.
Know the Limitations of Your Cooktop
It isn’t just pressure canners that have changed. Cooks also have the choice of a variety of kitchen ranges. The type of cooktop you use can determine how efficiently and safely a pressure cooker works.
Halogen – A halogen cooktop heats up within seconds and then cools off quickly. This type of burner makes it difficult to use a pressure cooker accurately. In comparison, when cooking on electric stoves, the pressure cooker is brought to pressure using the maximum heat. Then, you turn it down to the lowest heat setting to maintain the pressure. One way to make the halogen cooktop work is to switch from the large burner with high heat and the smaller burner that is pre-heated to the lower heat. The slow heat-up of an electric range makes it similar to that of a halogen.
Induction – Induction stove tops bring the pressure cooker to the desired pressure much faster than on a gas stove. The contents might boil, release vapor, and reach pressure before the lid gets hot. You may be able to can on an induction top if you increase the cooking time by two or three minutes.
Glass Top – Glass cooking tops are extremely popular but they aren’t recommended for canning food. One reason is that the heat might be reflected back down onto the surface, causing damage to the stove. The heavy weight of the pressure cooker getting scooted on the stove can cause scratching and the weight can even crack the glass top.
Another problem with glass tops is that the burners of some will shut the heat off when it gets too hot under the canner. This can result in the food being under-processed and unsafe.
You probably already know that all types of cookware don’t work equally well on glass tops. This is true for both pressure cookers and bath cookers. Look for cookers with smooth bottoms and those made of stainless steel.
Gas Stoves - These are the ideal stove type for pressure cooker canning and they require no adjustments to the heating process.
All types of stoves might be used for canning foods depending on the manufacturer and model. Check your manual to see what they recommend and whether it’s safe to use a pressure cooker or water bath on your cooktop.
More Tips on Safe Canning
- It might seem like any food can be canned, but there are some that shouldn’t be. For example, eggs and dairies like cheese or milk, pureed squash, flour, pasta, rice, oil, or nut butter. For some of these, it is a safety issue where bacteria might not be killed. For others, it is an issue of food quality.
- Only use Mason jars and matching lids for canning food. Use new lids each time to ensure you get a tight seal.
- Rely on trusted recipes instead of trying something new.
Safe Canning Starts at Grange Co-op
Having the right tools goes a long way toward canning food safely. Shop at Grange Co-op for top-brand Mason jars, pressure cookers, water bath canners, mixes, and more. Have questions? Contact us online or stop by your local Grange Co-op store.