Reduced-Sugar Blackberry-Plum (or Raspberry-Plum) Freezer Jam

INGREDIENTS

2 1/3 cups

blackberries or red raspberries

2 cups

(1 to 1 1/4 pounds) slightly underripe purple or red plums, pitted and chopped into 1/2-inch pieces

2 tbsp

water

to 2 1/2 tablespoons lemon juice (use 2 1/2 tablespoons for very ripe, sweet berries)

1/2 tsp

finely grated lemon zest

2 1/3 cups

sugar

2 tbsp

powdered less- or no-sugar-needed pectin, such as Sure-Jell or Ball Fruit Jell