Q: I have some semisweet chocolate squares with an expiration date of September 2011, but the chocolate has turned white or pale. Is it OK to use?

A: The white haze is called bloom. It happens when chocolate is stored improperly, usually when it is kept somewhere that is too warm or it is exposed to extreme temperature changes. A couple of things can cause it. Either moisture dissolves some of the sugar in the chocolate, then rises to the surface, leaving sugar crystals behind when the moisture evaporates. Or, more commonly, the fat or cocoa butter in the mixture separates and rises to the surface.

If you’re using the chocolate in a recipe where it will be melted, you can still use it. Nibble a little bit first to make sure it doesn’t have an off flavor.

Good-quality chocolate is delicate, and it’s certainly expensive, so it’s worth storing it correctly. Keep it well wrapped in a dark place where it doesn’t get too warm or too damp.