Using One of Summer's Delights
When fresh blueberries are at their peak, it makes sense to go beyond a handful in your morning cereal or the occasional blueberry pie. Cooking down the berries allows you to save them for the dead of winter or to use them later for all sorts of summer treats, from sauces and drinks to jams, jellies and frozen pops. Fresh blueberries keep in the refrigerator, unwashed, for one to two weeks if you spread them out in a single layer on a plate or baking sheet.
Jams Without Pectin
If you plan to enjoy blueberry jam with pieces of the berries still intact within a month or two, you don't need to add any water at all, nor any thickening agent, since the berries themselves will thicken naturally. Simply bring sugar and water to a boil, and stir the mixture long enough for the sugar to dissolve in the berry juices. Cook the mixture until it reaches the consistency you want, anywhere from 5 to 10 minutes. Stir frequently, so the jam doesn't burn or stick to the pan, and use as much or as little sugar as you like.
Jams and Jellies With Pectin
Jams thickened with pectin achieve a thick consistency more quickly than jams made without pectin and thus retain more of the fruit's juices and color. For jams made with pectin, use about 3/4 cup of water for each 5 cups of berries, and one box, or 1 3/4 ounces, of powdered pectin. Bring the ingredients to a full boil on high heat, and continue cooking the jam for about 1 minute, stirring all the time. If you want jelly, with no remnants or seeds from the blueberries, strain the mixture through a sieve or cheesecloth before pouring it into jars.
Purees and Sauces
Blueberry purees and sauces work well as toppings for ice cream, pancakes or pound cake, or as the base for a fruity barbecue sauce. You can also use the puree in lemonade or smoothies and for making frozen pops. In a blueberry puree, the berries achieve a smooth, somewhat thick consistency, while in a blueberry sauce, the berries achieve a similar consistency but may contain pieces of the berries. For both sauces, cook the blueberries over medium heat with no water and as much sugar as you want until the berries reach the consistency of loose sauce, about 7 or 8 minutes. For a puree, mash the berries or pulse them in a blender or food processor until smooth.
Compotes
Although you can use a blueberry compote in the same way you would purees and sauces, your goal in making the sauce is to cook the berries gently enough so they remain whole. Use 1/2 teaspoon of cornstarch for each cup of blueberries, along with 3 tablespoons of water and about 1 1/2 tablespoons of sugar. Cook the ingredients over medium-low heat until the cornstarch turns clear and the mixture begins to thicken slightly, about 5 minutes. Be careful when you stir, so the blueberries break apart as little as possible.