How to Can Tomatoes

Canning is an age-old domestic art that’s seeing a revival in time with today’s passion for locally grown food, fresh high-quality ingredients, and charming DIY kitchen projects.

Take a tool inventory
To get started you’ll need:

• Litre-size (4-cup capacity) canning jars (a.k.a., Mason jars).
• Metal lids and rims.
• Large stock pot with a cover (or a water bath canner).
• Rack for placing inside the bottom of the pot is essential – if the jars touch the bottom, they can crack open.
• Jar lifter – it’s a canning tool shaped like a set of large tongs with rubber-coated ends that help to safely lift jars out of boiling water. You could also use tongs – and caution – for this purpose.
• Finally, a chopstick or stir stick is essential for running along the inside edges of the jar to eliminate air pockets before sealing shut.

Prep jars
Thoroughly wash jars and bands. Keep jars warm in a 225˚F (110˚C) oven. Sterilize lids in boiling water for five minutes and leave in water until ready to use.

Prep tomatoes
In a large pot of boiling water, blanch tomatoes for 30 to 60 seconds or until skins loosen. Remove tomatoes to an ice bath, immediately drain and peel. Core and trim tomatoes or any bruised spots, then quarter and place in a large pot over high heat. Heat tomatoes through until juices begin to boil.

Fill ‘em up
When canning, it’s important to leave a ½-inch (2 cm) headspace – the gap between the top of the food and the lid. One jar at a time, fill with tomatoes and juices.

Add acid
Canned foods need to reach a certain acidity level to ensure they are preserved safely. For every 1-litre jar of tomatoes, add ½ tsp (2 mL) citric acid or bottled lemon juice.

Bring to boil
Now it’s time to seal your jars. Wipe jar rims clean with a damp towel and place lid on. Screw on band until tight (do not force it). Place jars in canning rack or gently lower into a pot on top of the rack at the bottom. Without pouring on top of jars, add enough simmering water to cover jars by 1 to 2 inches (2.5 to 5 cm). Cover pot and bring to rolling boil. Boil 1-litre (4 cups) jars for 45 minutes. Remove from heat.

Cool it down
Using a jar lifter or tongs, gently transfer jars from pot to rest on a clean towel. Let cool completely. Do not adjust bands. Inspect seals: lids should curve inward and shouldn’t move when pressed. Refrigerate unsealed jars and use within three days. Store properly sealed jars in a cool, dry, dark place. Refrigerate after opening.