bloom [bloom] noun
A light, whitish coating appearing on some foods. The hazy look on blueberries is called bloom. When chocolate exhibits a whitish/grayish appearance on the surface, it is called fat bloom, and is a result of chocolate being out of temper (meaning the cocoa butter has separated and come to the surface). Sugar bloom, caused by moisture, is another type that can affect chocolate and can be hard to differentiate visually from the fat version. Both kinds can be prevented by proper storage – assuming the chocolate is in good temper to begin with. Chocolate should always be stored airtight at cool room temperatures.