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Blackberry jam

An average of 5.0 out of 5 stars from 3 ratings
Blackberry jam
Prepare
less than 30 mins
Cook
10 to 30 mins
Serve
Makes 6 x 225ml/8fl oz jars

Making a batch of blackberry jam is a wonderful way to bottle the last of summer’s warmth. A sugar thermometer guarantees a good set, but if you don’t have one, you can use the traditional method of testing for set on a chilled plate.

Ingredients

  • blackberries: 1.2kg/2lb 10oz blackberries
  • caster sugar: 700g/1lb 9oz caster sugar
  • lemon: 1 lemon, juice only

Method

  1. If you don’t have a sugar thermometer, a few hours before you want to make your jam, put a couple of small plates or saucers into your freezer.

  2. Wash the blackberries and add to a large, heavy-bottomed saucepan. Cook over a medium–high heat for 8–10 minutes, stirring occasionally, until most of the blackberries have broken down and the remaining berries are almost submerged in their juice.

  3. Begin to add the sugar to the berries, a third at a time, stirring between each addition, then add the lemon juice. Bring the mixture to the boil, then turn the heat down slightly to a gentle rolling boil and simmer for 8–10 minutes, until the jam reaches 105C/220F on a sugar thermometer. At this stage the bubbles in the jam will have changed from large to small, indicating that most of the water from the fruit has evaporated.

  4. If you don’t have a sugar thermometer, you can test if your jam has reached setting point using your pre-chilled plates. When you’re ready to test the set, remove a plate from the freezer and drop a teaspoon of jam onto it. Leave it for a moment, then run your finger through the jam. If the jam crinkles a little on the surface as though it’s beginning to form a skin, it’s ready to be jarred. If the jam remains runny and the line your finger has created disappears in the jam, cook it for a few more minutes and test again with your second chilled plate.

  5. Carefully divide the jam between six warm sterilised jars and seal with sterilised lids. The jam will keep, unopened, in a cool dark place for 12 months. Once open, store in the fridge and eat within two weeks.

Recipe tips

To sterilise the jars, preheat the oven to 110C/100C Fan/Gas ¼. Wash the jars in hot, soapy water, rinse thoroughly, then put them on a baking tray (rim side up) in the oven for 30 minutes. To sterilise the lids, put them in a small saucepan of boiling water and boil for 10 minutes. Jar your jam when it has reached setting point and while the jars and lids are still warm following sterilisation.

For a more acidic, less sweet jam, stir a tablespoon of apple cider vinegar through the mixture before jarring.