Pulse blueberries in a food processor, or gently crush 1 layer at a time with a potato masher or pastry cutter. Set aside.
In a heavy-bottomed saucepan, combine 3/4 cup white grape juice and 1 tbsp lemon zest. Bring to a low boil.
Whisking constantly, slowly add the pectin into the juice mixture until fully incorporated. Cook for 1 minute at a low boil, whisking constantly.
Add the crushed blueberries and 1 1/4 cup sugar to the juice/pectin mixture. Stir to incorporate.
Bring to a gentle boil and cook for 1 minute while stirring constantly. Reduce heat slightly if the jam begins popping.
Remove from heat and continue to stir gently for 3 minutes.
Use a funnel and ladle the jam mixture into your preferred containers, leaving 1/2 inch of space between the tops of the jam and the tops of the jars.
Place lids on the jars, and allow them to sit at room temperature for 2 hours.
Freeze jam or store in the fridge for up to 3 weeks.
Notes
Good for three weeks in the fridge or 9-12 months in the freezer.Jam is ready to use after the 2-hour rest. It does not need to be frozen first to be ready to use.No-Cook Instructions:I recommend you use 2 tbsp of lemon juice instead of lemon zest if you're doing the no-cook version.
Pulse blueberries in a food processor, or gently crush 1 layer at a time with a potato masher or pastry cutter.
Stir in sugar, lemon juice, and let sit for 15 minutes.
Add pectin and stir constantly for 3 minutes.
Pour into jars, leaving 1/2 of headspace.
Put lids on and allow the jars to sit at room temp for 2 hours.