How to Buy:
Look for berries that have the silvery bloom coating, are plump and uniform in size, and are not shriveled. If the blueberries do not have the bloom coating, it is an indication that they are not fresh or that they have been washed. Washed berries will not keep as long as unwashed berries. The blueberries should be deep-purple blue to almost a bluish black color. If they have a reddish color to them, they are not ripe yet, but can still be used if they are going to be cooked. Check the bottom of the blueberry container for mold and look for blue stains from the berries. Berries should be firm, dry, and move freely in the container. The blue stains may be from crushed or overripe berries.
When buying frozen berries, be sure they are separated and loose in the bag. If they are frozen into a clump, it is a sign that they have at least partially thawed and then been refrozen.