What is the thin white coating that happens to dark chocolate?
This is called blooming. Blooming: There are two kinds of bloom that form on the surface of chocolate: both are temperature-related and both make the chocolate look suspect and unappetizing. With fat bloom, the chocolate loses its gloss: a powdery white or tan film forms on the surface. This is due to improper storage, poorly tempering, lack of tempering, or changes in temperature. Heating chocolate above 70°F, as well as repetitive heating and cooling, will cause microscopic cocoa butter particles to join together, leaving particles of sugar and cocoa uncoated. The bloom is the cocoa butter that has separated and risen to the surface. In some cases the chocolate may become soft or crumbly. While bloom diminishes the appearance of the chocolate, it does not alter the taste and is not harmful. Chocolate with fat bloom can be eaten although it may taste drier. Fat bloom can be avoided by storing chocolate a constant temperature. Sugar bloom is caused by condensation, due to excessive moi