Canning is a great way to make the most of local fruits and vegetables, which are particularly abundant in the fall. Follow our step-by-step guide on making delicious preserves safely.
Safe Canning
A pressure canner is essential for safely preserving low-acid foods like vegetables, meats, soups and sauces. It heats jars at a high temperature under pressure, destroying bacteria, yeasts and moulds, which play a factor in spoilage.
1- Preparing the Jars
Mason jars are designed for canning. They come in different sizes, ranging from 125 ml to 1 L, chosen according to the foods you want to preserve. It’s important to check that they’re in good condition before using them. Discard any with chipped rims or cracked glass.
Place the well-washed and rinsed jars on a support rack inside a large pot. This keeps the glass jars from hitting the bottom during processing. The pot must be deep enough so that the water completely covers the jars without boiling over.
Leave the jars in boiling water for about 5 minutes and keep them in very hot water until it’s time to fill them. Remove them using canning tongs, which have a rubber coating that prevents slipping and protects the glass from thermal shock.
2- Preparing the Airtight Lids
The lid consists of two parts, a metal band and a sealing disc, that ensure an airtight closure for the Mason jars. The bands are reusable, but check that they’re not rusty or deformed before use.
As for the sealing discs, they must be new since they’re airtight only once. Place them in hot, but not boiling, water, to soften the rubber band around the rim that promotes an airtight seal. Keep them in hot water until ready to use.
3- Filling the Jars
Fill the jars using a funnel, leaving a 0.5 cm to 2.5 cm clearance between the food and the rim. This clearance is referred to as a headspace, and it’s necessary for expansion during heat processing. Using a spatula, slide it along the glass to remove any air bubbles that may have formed. Adjust the headspace as needed.
Carefully wipe each jar rim with a clean damp cloth to remove any residue that could prevent sealing. Place the sealing disc on top and then screw on the band until it meets resistance. Tighten by a quarter turn only without overtightening, in order to allow air to escape during heat treatment.
4- Sterilizing in Boiling Water
Jars filled with acidic foods or foods acidified with vinegar or lemon juice are processed in boiling water. Using tongs, place them on a support rack inside the pot, ensuring they’re covered with 1 inch (2.5 cm) of water. Bring to a boil, covered.
Processing time varies with each recipe. Start timing when the water reaches a full rolling boil. Maintain the boil until the processing is complete and then remove the jars from the water.
5- Cooling and Storing
Once processing is complete, remove the jars with the tongs, being careful to not tilt them. Place them on a rack or a folded dishtowel. This will prevent thermal shock between the cold work surface and the hot glass jars.
As the jars cool, the metal disc will bend inward and emit a soft “pop” sound. After 24 hours of cooling, check that the covers are well sealed. If the centre doesn’t move when you press down on it, sterilization is successful.
Jars that haven’t been sealed well should be refrigerated and their contents consumed quickly. Store the rest in a cool, dark place.