I love the blueberries you find in store bought pies and muffins, so I tried to make them myself. First I used fresh blueberries, which turned out to be more sour than sweet. I tried letting them sit until they seemed to almost go bad - no luck, still sour. So after hearing about how frozen fruits are frozen at their peak ripeness, I buy some frozen blueberries. And they're still sour. Do stores treat their berries with sugar or something, or do I just have really horrible luck?