Summer means tomato salads, gazpacho and salmorejo but when tomato production is in full flow and supplies are starting to mount up, that’s the time to start canning. Over the years, I’ve experimented with all different kinds of canning methods but this is now the method I use to ensure that we have tomatoes all year.
I use a pressure cooker but if you haven’t got one, then use a large pan and cook for longer.
The first job is to clean your jars. My jar of choice is the 400g one they sell chickpeas, pinto beans, etc. in. Clean all the jars and lids in hot, soapy water and rinse thoroughly. Leave to dry upside down on a tray with a teatowel until you need them. Discard any lids with dents in.
Wash and chop the tomatoes into pieces, removing the central core. Transfer to a large, wide frying pan or wok with some salt and bring to the boil. The amount of salt will obviously depend on the size of the pan, but generally speaking I will add 3 teaspoons for a very large pan. We normally do this part of the process outside on the barrel burner. Cover and cook for about 5 minutes or so until the tomatoes are softer and have started to release their juice.
The next part of the process is to separate the tomato pieces from the tomato juice. You’ll need two colanders: place one over a large pan and the other on a dish high/large enough to catch the juice. Use a slotted spoon to transfer the tomato pieces into the colander on the dish, using a swirling action to remove as much juice as possible but the tomato pieces shouldn’t be too dry.
Use a jam funnel and a dessert spoon to fill the clean jars with tomato pieces to the “shoulder” of the jar. Top up the jars with the tomato juice to about 5-7mm from the top and use the spoon to make sure that there are no air pockets in the jars. Put the lids on the jars and close securely but not overly tight.
You will always have more juice than you need but you can use this for soup or return to the pan and reduce down to form a concentrated tomato paste or sauce.
Put a trivet or silicone mat on the bottom of the pressure cook and place the jars on top. Half fill the pressure cooker with water, close the lid and bring to pressure. Cook at pressure for 15 minutes. Turn off the heat and leave for 5 minutes. If you have a quick-release cooker, gently run under cold water and release the pressure.
Remove the jars and put somewhere to cool. After about 30 minutes, you should hear the lids popping as they contract. Leave to cool completely. If any of lids has not contracted or if juice has escaped from any of the jars, replace the lids, add some more juice and redo with the next batch.