Allow the blueberries and cranberries to thaw. Puree until thick but runny. Strain juice into a large pot, reserving the berry pulp. (Best to put the strainer/colander onto a plate, in the meantime.)
Add sugar and grape juice to pot, stir until well combined. Add water to just over 1 gallon of total liquid. Once you’ve added enough water, add the berry pulp back into the pot. Heat to ALMOST boiling, then simmer gently for 10 minutes. Stir in acid blend, enzyme, and nutrient.
Pour mixture into a freshly sanitized 1.5 gallon fermenting bucket. Cover with sanitized lid and air lock, allow to cool to room temperature (overnight).
The next morning, give the mixture a quick stir with a long, sanitized spoon, and – using sanitized equipment – take a gravity reading. Keep track of the number! (This is an optional step, but will allow you to calculate your final ABV %)
Sprinkle yeast into fermenter, cover with sanitized cover and air lock. Within 48 hours, you should notice fermentation activity – bubbles in the airlock, carbonation and /or swirling in the wine must. This means you’re good to go!
After a week or so, use your sanitized siphon setup to rack the must into a freshly sanitized 1 gallon carboy. Put the carboy somewhere cool (not cold!), and leave it alone for a month or so.
Using sanitized equipment, rack the lingonberry wine off the sediment, into a clean, freshly sanitized 1 gallon carboy. Cap with sanitized airlock, leave it alone for another 2-3 months.
Rack one more time, leave it for another 3 months or so.
When your wine has been racked a few times and shows NO more fermenting activity for a month or so (no bubbles in the airlock, no more sediment being produced, you can move on to bottling.
Follow the instructions on your selected type of wine stabilizer to stop fermentation. For potassium sorbate, this needs to be done 2-3 days before bottling.
Using sanitized equipment, take a gravity reading, then rack the wine into clean, sanitized bottles. Cork.
Store wine bottles in a cool, dark place. Wine tastes even better after aging for a year.