Ingredients:

  • 4 cups (approximately 600g) fresh blueberries, washed and stemmed
  • 3 cups (600g) granulated sugar
  • 1/4 cup (60ml) lemon juice, freshly squeezed
  • 1 package (1.75 oz or 49g) powdered pectin
  • 1/2 teaspoon (2.5ml) unsalted butter (optional)

Instructions:

  1. Sterilize canning jars and lids according to manufacturer's instructions (or boil in water for 10 minutes). Keep jars hot until ready to fill.
  2. In the large saucepan, combine blueberries, lemon juice, and butter (if using).
  3. Sprinkle the powdered pectin evenly over the blueberry mixture.
  4. Bring the mixture to a full rolling boil over high heat, stirring constantly. Gently mash the blueberries with the back of a spoon or potato masher as they cook.
  5. Add the granulated sugar all at once, stirring constantly until dissolved.
  6. Continue to cook over high heat, stirring constantly, until the jam reaches the gel stage (220°F (104°C) on a candy thermometer, or passes the cold plate test - see below).
  7. Remove the saucepan from the heat. Ladle the hot jam into the prepared jars, leaving ¼-inch headspace.
  8. Run a non-metallic spatula or bubble remover along the inside of each jar to release any trapped air bubbles.
  9. Wipe the rims of the jars clean with a damp cloth. Place the lids on the jars and screw on the bands until fingertip tight.
  10. Place the filled jars in a boiling water bath canner (or a large pot with a rack). Ensure jars are completely covered with water (at least 1 inch above the lids). Bring the water to a boil and process for 10 minutes.
  11. Remove the jars from the canner and let them cool completely on a towel-lined surface for 12-24 hours. As the jars cool, you should hear a popping sound, indicating that the lids have sealed properly. Check the seals by pressing down on the center of each lid – it should not flex.
  12. Store sealed jars in a cool, dark place for up to 1 year. Unsealed jars should be refrigerated and consumed within a few weeks.