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a jar of homemade blackberry jam on a grey table.
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Blackberry Jam (Without Pectin)

A quick, small-batch jam made with fresh or frozen blackberries, sugar, lime, and cornstarch. Ready in about 15 minutes — no pectin needed.
Course Breakfast, Brunch
Cuisine American
Prep Time 5 minutes
Cook Time 10 minutes
Cooling Time: 1 hour
Total Time 1 hour 15 minutes
Servings 10 serves
Calories 106kcal
Author Peter G

Ingredients

  • 250 g blackberries fresh or frozen; wild if available (See Note 1)
  • 220 g sugar white granulated; caster or brown sugar can also be used (See Note 2)
  • 180 ml water divided (120 ml for cooking + 60 ml for slurry)
  • 1 lime juiced (lemon is a fine substitute; zest optional) (See Note 3)
  • 15 g cornstarch cornflour (See Note 4)
Metric - US Customary

Instructions

  • Combine the blackberries, 120 ml (½ cup) of the water, sugar, and lime juice in a medium–large pot over medium heat.
    250 g blackberries, 220 g sugar, 180 ml water, 1 lime
  • Bring the mixture to a boil and cook for about 10 minutes, until the berries have softened and the mixture turns a deep red. Skim off any foam that rises to the surface. (See Note 5)
  • Mash the softened berries thoroughly with a fork or potato masher.
  • In a small bowl, whisk the cornstarch with the remaining 60 ml (¼ cup) water to make a slurry. Stir the slurry into the berry mixture and mix vigorously. (See Note 4)
    15 g cornstarch
  • Increase the heat to high and cook for 2–3 minutes, stirring constantly (be careful of splatters!) until the jam thickens. (See Note 6)
  • Remove from the heat and let the jam sit for about 10 minutes. This allows the flavours to mingle and the jam to begin setting. (See Note 7)
  • Cool completely before transferring to sterilised jars. Seal with lids and refrigerate. (See Notes 8 & 9)

Video

Notes

Variations
  • Swap water for white wine or add a splash of Chambord.
  • Replace half the sugar with honey.
  • Infuse with cinnamon stick, ground cinnamon, or vanilla bean.
  • Add grated apple for natural pectin, or chopped peaches/plums for tartness.
Notes
  1. Note 1 (Blackberries): Fresh, ripe berries release more juice and flavour; frozen work straight from the freezer.
  2. Note 2 (Sugar): White sugar keeps flavour clean; caster dissolves faster; brown sugar adds caramel notes.
  3. Note 3 (Citrus): Lime juice/zest brightens the jam; lemon is a good substitute.
  4. Note 4 (Cornstarch): Always whisk with cold water first to prevent lumps; thickens quickly for a silky texture.
  5. Note 5 (Foam): Skimming foam while boiling improves appearance and texture.
  6. Note 6 (Pot size): A medium–large pot helps avoid splatters and ensures even cooking.
  7. Note 7 (Resting): Letting the jam sit 10 minutes off heat allows flavours to develop and begin setting.
  8. Note 8 (Jars): Sterilise in the dishwasher or with hot soapy water; dry thoroughly before use.
  9. Note 9 (Storage): Store in fridge up to 2 weeks, or freeze for longer storage.

Nutrition

Serving: 1serve | Calories: 106kcal | Carbohydrates: 27g | Protein: 1g | Fat: 1g