You can reduce the calories by using fructose, or fruit sugar. Frisana fruit sugar is sweeter than ordinary sugar, so you need up to a third less. It also has a greater preservative effect.
Prep time: 5 minutes, plus bottling
Cooking time: 20 minutes
450g (1lb) blueberries
100ml (4fl oz) water
300g (10oz) Fruisana fruit sugar
1. Place the fruit and water in a large saucepan and simmer gently for approximately 5 minutes.
2. Add the fruit sugar and stir until it has all dissolved.
3. Rapidly boil the conserve, stirring occasionally to prevent sticking or burning. After 15 minutes, test the jam to see if it has reached its setting point. If it does not wrinkle when you push it with a fingernail acriss the saucer, continue to boil rapidly and then test again after a short period.
4. When the jam has reached its setting point, take the saucepan off the heat and remove any scum that may have formed with a slotted spoon, or break it down by adding a knob of butter.
5. Carefully pour into a measuring jug into a measuring jug and pour into a measuring jug and pour into the steralised jam jars (using a jam funnel is you have one) and cover immediately. Once it has cooled completely, place in a cool, dark cupboard and refrigerate once opened.