There’s no better way of preserving the flavor of fresh blackberries than with this spreadable sweet treat.
- Rolling boil: A boil that continues to bubble as it’s being stirred.
- Gel point: When enough water has evaporated from the mixture, the jam has reached its gel point—the point at which it will thicken when cooled.
Lemon juice isn’t just about adding flavor to the jam. The acid in the juice helps the pectin gel, resulting in a ‘set’ jam.
To see if the jam has thickened, place a small dot of jam on a cold plate, and place in the freezer. Remove from freezer after 2 minutes, and run your finger through it. If the jam runs, it needs to cook a bit longer.
Cook Time Tip
The ripeness of berries can affect the cook time of jam. This jam could take anywhere from 20 minutes for very ripe berries to 50 minutes for less ripe berries.
- 2 pounds fresh blackberries
- 2 cups sugar
- 2 tablespoons fresh lemon juice
- ⅛ teaspoon kosher salt
- In a large glass or ceramic bowl, combine all ingredients.
- Let stand at room temperature, stirring occasionally, until blackberries have released their juices and most of sugar has dissolved, about 1 hour.
- Transfer blackberry mixture to an enamel-coated cast-iron Dutch oven. Bring to a boil over medium-high heat; mash with a potato masher or the back of a wooden spoon. Reduce heat until mixture is gently boiling. Cook, stirring frequently, until thickened, about 50 minutes. Remove from heat. Let cool for 30 minutes. Spoon into jars. Cover and refrigerate for up to 2 weeks.
Want more jam recipes? We’ve got plenty to choose from. Give our Peach-Ginger Jam and Plum-Strawberry Jam a try.