In Batch, a cookbook on everything related to preserving, by Dana Harrison and Joel MacCharles, this fermented soda recipe combines techniques from jam making as well as soda making with yeast so you don't have to use a soda machine for the carbonation. It's perfect for the summer!
Drink this within a month of making it. For this recipe, you'll need cheesecloth, bottle sanitizer, plastic bottles, caps and bottling equipment.
Wash the blueberries and lightly crush them.
Place the berries, maple syrup, ginger, and 3 cups of the water in a pot. Turn the heat to high and simmer, uncovered, for 20 minutes, mashing the berries as the liquid reduces. Add more water if the mixture thickens.
Let the mixture cool, then puree it in a blender or food processor until smooth.
Strain the liquid through a fine sieve. (Squeezing it will add flavor but will result in a cloudier product.) When the mixture has cooled to room temperature, add lemon juice, port, champagne yeast, and a pinch of salt.
Divide this blueberry concentrate between the bottles. Add filtered water to each until they are ¾ full. Place the lid on top, and shake the contents to mix. Taste, and add additional maple syrup if desired. Add additional filtered water until 1 inch of headspace remains in each bottle.
Place the caps on the bottles and leave in a warm, dark place in your kitchen. Squeeze daily to test for carbonation. When the bottle is difficult to squeeze (12–48 hours), it’s done.
Store this in the fridge (this will prevent explosions by slowing fermentation). Open the bottles slowly over a bowl as this soda can be a little volatile!