Wash in cool water, drain well, remove any stems or damaged berries, and spread on towels to dry completely. The natural waxy coating (bloom) on blueberries helps protect them during freezing, so handle gently to preserve it.
Flash freeze: spread dry blueberries in a single layer on a parchment-lined sheet pan. They are small enough that they can be close together without sticking, but avoid piling them. Freeze until solid (1 to 2 hours), then transfer to freezer bags. Press out air and seal.
Blueberries generally do not need a sugar or acid treatment — their natural chemistry and thick skin protect them well during frozen storage. If you want sweetened berries for topping desserts, you can toss with sugar before freezing (½ cup sugar per quart).
8 to 12 months.
For baking: use directly from frozen. Add an extra minute or two of baking time. Toss frozen berries in a tablespoon of flour before adding to muffin or cake batter to prevent them from sinking. For smoothies: use frozen. For eating: thaw in the refrigerator.