This recipe uses less sugar than most recipes to ensure the flavor of blackberry comes through. This reduces the shelf life of the jam, however, so it should be stored in the fridge and always take care to use a clean spoon. Make sure to sterilize your jars carefully before pouring in the jam. A good rule of thumb is to use about 1/3 sugar in relation to the weight of the berries.
- Rinse the berries thoroughly. Discard any berries showing the slightest sign of mold.
- Put the remaining berries in a pot along with the water and boil for about 10 minutes until they start to turn tender. Add sugar.
- If you’re using vanilla, scrape the seeds out of the halved pod and add both pod and seeds to the mixture. Boil for an additional 10 minutes. If you don’t like whole berries in your jam, give it a gentle whiz with a hand blender. Add lemon juice to taste.
- Test the consistency of the jam using a frozen spoon. Continue to cook until you reach the desired consistency. Add powdered pectin, available in most supermarkets, to help the jam to set faster. Follow the instructions on the package.
- Pour the jam into clean, scalded jars that have been sterilized with sodium benzoate or vodka. Place the lid on immediately.
- Store in a cool, dark place.