Canning is an economical way to save your recent grocery haul from rotting in your crisper drawer. In many cases, fruits and vegetables that are canned right after they are harvested can be just as nutritious or even more than off-season fresh produce.
Simply put, canning is a method that preserves fresh foods and involves glass jars and heat. It processes foods at high temperatures, removes all the air and then vacuum-seals the food in jars to prevent spoilage.
These important steps kill contaminants, making it possible to store canned food for long periods of time.
Fresh produce contains water, which is why it's perishable — and contaminants, including microorganisms, food enzymes, oxygen and loss of moisture can wreak havoc on canned food if procedures are not properly followed (more on that later).
The next step is deciding what you're going to can. You can choose ingredients to be raw-packed or hot-packed.
- Raw-pack method: The jars are filled with raw food like diced carrots and then covered with boiling liquid.
- Hot-pack method: This involves filling jars with precooked, hot food rather than raw. This would include jam or cooked fruits and vegetables, which are then covered with boiling liquid. In the case of fruits, the liquid should be sugar syrup.
Finally, let's talk about how to actually do the canning. There are two main home canning methods: water-bath canning and pressure canning. Both methods work well for a variety of foods, so choose the best method for you.
Canning is not always the simplest procedure, but we're making it as easy as possible! Here are the basic steps for water-bath canning and pressure canning.
Water-bath canning can use a pot you may already have on hand as long as it can accommodate six to eight jars and is at least 3 inches taller than the jars.
The pot should fit over one burner and the lid must be tight-fitting and stay in place over boiling water. The combination of time and temperature with water-bath canning destroys contaminants while creating a vacuum seal.
Foods That Work Best for Water-Bath Canning
Choose high-acid foods such as tomatoes, fruit, jam, salsa, pickles and chutney.
What You’ll Need
- Water-bath canner or a large stockpot with a lid and a canning rack (note: you can use a cooling rack if necessary)
- Glass canning jars, lids and rings
- Jar lifter to remove jars from the canner
- Kitchen utensils: wooden spoon, ladle, long tongs, jar funnel, spatula
- Potholders and clean kitchen towels
- Foods to can
How to Do It
- Wash the canning jars, lids and rings in hot soapy water or in the dishwasher, and then rinse them thoroughly.
- Fill the water-bath canner or stockpot at least halfway with water and place on the stove with the rack placed inside. Turn on heat to high and bring to a boil; then, lower to a simmer (180 degrees Fahrenheit) and cover pot.
- Place empty jars in the canning rack in the hot water.
- Prepare your high-acid food to go into the jars by thoroughly rinsing them under running water.
- Using a jar lifter, remove a pre-heated jar. Fill the jar with prepared food. For items like jam, use a jar funnel. For items like fruit or vegetables, pack the food in the jar firmly but do not crush the produce. Then, add boiling water or liquid to cover the food and leave a half-inch of headspace.
- Use a spatula to release any trapped air in the jar.
- Clean the rim and top of the jar to remove any food.
- Center the lid on the jar so that the sealing compound is directly on the rim of the jar. Place the ring and screw on firmly, but stop turning when you feel resistance.
- Place the jar back into the pot and repeat until jars are filled and returned to the pot. Water should cover the jars by at least 2 inches.
- Place cover back on the pot and bring to a rolling boil. Set a timer for the required amount of minutes based on the item being canned.
- Once complete, turn off the heat, remove the cover and allow jars to remain in the water for 5 minutes.
- Remove the jars and set them on a towel, allowing them to rest for 12 to 24 hours. As the jars cool, you may hear a hollow popping sound.
- Once cooled, remove the metal rings and make sure the lids are sealed and curve down slightly. If you press the center of the lid, it should not move.
- Label the jars with the type of food in each and the canning date. Then, store them in a cool, dry, dark place. For best results, open within one year, although they should last up to 18 months.
Pressure canning requires the purchase of a steam-pressure canner, which can heat foods at 240 to 250 degrees Fahrenheit — the temp the USDA recommends low-acid foods should be sterilized at to avoid food poisoning.
This combination of time and temperature destroys food-borne bacteria and creates a vacuum seal to prevent spoilage. A steam-pressure canner has a cover that locks in place, allowing the steam to build inside and reach the appropriate temperature, similar to a pressure cooker.
Foods that Work Best for Pressure Canning
These foods include low-acid vegetables (most fresh veggies and fruit, except for citrus, are low-acid) and chili.
This method is the same as the water-bath canning method detailed above. However, instead of the large stockpot and water, follow the manufacturer's instructions that accompany the pressure canner.
How to Avoid Food Poisoning From Canned Food
Great care should be exercised in the canning of any food. It is vital to follow directions and processing methods to prevent spoilage and the growth of Clostridium botulinum, which causes botulism, a deadly form of food poisoning.
Harmful bacteria can multiply rapidly given the proper environment for growth, which includes moist low-acid food, temperature in the danger zone (40 degrees to 120 degrees Fahrenheit) and less than 2 percent oxygen, according to the USDA.
Before serving home-canned food, it is important to inspect the jar for spoilage. The lids should be tight and still depressed at the center, which indicates a proper seal.
The following may indicate that the food may be contaminated:
- The lid is swollen
- There are streaks of dried food from the top of that jar
- There is mold on the jar
- Bubbles are rising in the jar
- Liquid or food is seeping out of the jar
- The color of the food looks unnatural in any way
- The liquid is cloudy
If any of these signs are present, do not open or eat the contents of that jar. A properly sealed jar should "pop" and "whoosh" as you pry off the lid. There should be no off odors, gas, signs of fermentation or mold.
If any of these items occurred, discard the jar immediately (without tasting the food first) into a heavy garbage bag that is closed securely and properly separated from accidental handling by any children, pets or wild animals.
Remember, when in doubt, throw it out!