About a month ago, I tried baking a carrot cake mix only to find, in trying to break up the lumps with a spoon, the orange-y carrot bits began dissolving into the mix and which vanished altogether by the time most of the lumps were gone. Instructions specify an electric beater for X minutes and the carrot bits would probably have survived had I used one. The blueberry bits in their blueberry muffin mix ought to behave similarly.