How to preserve tomatoes (or jams or pickles or chutneys or jellies)
1. Start boiling.
Boiling water in the canner usually takes a while, so get it started right away. Fill a very large pot that can accommodate jars (each must have space around it) with at least 2 in. of water to cover. This pot is used only for processing filled jars (use another large pot for cooking the preserves).
2. Clean the jars.
Make sure the jars and screw bands are perfectly clean; a cycle through an empty dishwasher is ideal. Always use fresh flat lids.
3. Prep and cook.
Get the good stuff ready to fill the jars! For tomatoes, core, blanch, then drop into ice water. Use a knife to pull the skin away easily.
4. Fill the jars.
Use a clean canning funnel and ladle to fill each jar. Always follow the recipe’s instruction for headspace (the space between the level of fruit and the sealing lid). Wipe jar rims with clean paper towel. Carefully place the flat sealing lid on top with a magnetic stick. Tighten the screw band only just enough for it to stay on the jar (it has to leave enough room for the air to escape).
Preserving 101: Recipes, tips and ingredients to get you started
5. Preserving time.
Use canning tongs to carefully place the jars into the canner of boiling water. Filled jars must be covered by at least 2 in. of water. Start the timer on the processing when the water comes to a full rolling boil. Keep the water boiling for the entire processing time.
6. Check the lids.
Let processed jars stand at room temperature for 24 hours. Check that lids have sealed properly by pressing them. They should be flat and not pop up. Any jars that haven’t sealed can be stored in the fridge and used within two weeks.
Essential canning gear
Plus, check your pantry for:
Bottled lemon juice
It’s the only way to ensure a standardized acidity.
Use regular white granulated sugar to make sure results are consistent
The most common acid used in preserving. Don’t substitute another type.
A natural fibre found in fruits that helps jams and jellies to “jell” or set. You can go without it but you’ll have to cook preserves longer, which makes them less juicy and less fresh-tasting. Pectin* lets the flavours of the fruit shine through. Many fruits (such as pears) are naturally high in pectin; you can even make your own by cooking down apple peels and cores.
*You can find powdered and liquid pectin at hardware and grocery stores, especially in the summer. Use whichever the recipe calls for, as the two react differently.
Watch: A simple way to de-seed tomatoes