We-ve all had it happen. Your baking chocolate chip cookies or a batch of homemade brownies and you take the chocolate from the cabinet to find it speckled with white spots. The white spots are sometimes confused with mold, or even mildew and thrown away. Those little white spots do not mean that the chocolate has gone bad. It just means that the chocolate has bloomed.
Chocolate blooms in two situations. One is when it has been exposed to fluctuating temperatures, like in a cabinet over the stove. The chocolate starts to melt when the temperatures rise above 75 degrees. I found some more information here. When the temperature drops the cocoa butter separates and comes to the top. This is what forms the in a fat bloom.
The other type of bloom is sugar bloom. It is less common than a fat bloom. Where fat bloom is cause by temperature fluctuations, sugar bloom is caused by fluctuations in moisture. If a chocolate bar is exposed to humid conditions and then dry conditions, the sugar will come to the top as is dries.
To prevent either type of bloom chocolate, even unopened chocolate, should be stored in an airtight container and then placed in a cool, dry place. Places to avoid are cabinets over heat generating appliances. This includes appliances such as the stove and oven, dishwasher, and slow cookers. Another place to watch out for are cabinets close to windows.
Don-t throw away bloomed chocolate! It is still good to eat. Bloomed chocolate may seem unappetizing because of the white spots, but it is still safe to eat. It may have a grainy texture or seem to have a less chocolate flavor. Because of these texture and flavor issues it is best to use the bloomed chocolate in recipes that call for baking or melting.