Why chocolate turns white
Chocolate is one of the most fabulous treats known to man, which is why it is called the food of the gods. If you have ever been surprised after opening your favorite chocolate to find it white instead of the usual shiny brown, you probably wondered why chocolate turns white.
Chocolate is a complicated creation. Although tempering chocolate is a scientific process, even the best chocolate manufactures with world-class food scientists still get it wrong sometimes. When they get it wrong, the chocolate turns white, as does the badly tempered chocolate of your favorite local chocolatier.
So why does chocolate turn white? The white that you see is called bloom, fat bloom, to be precise. Fat bloom happens when liquid fat migrates through microscopic pores in the chocolate and crystallizes on the surface. Fat Bloom is caused by the instability of the fat content in chocolate. The fat that blooms is cocoa butter.
Cocoa butter gets extracted by the mechanical pressing of chocolate liquor. This process separates the fat from the chocolate liquor and is also how the cocoa powder is produced.
Are you still with me? OK good cause, this is where things get tricky. Cocoa butter is a triglyceride. There are three fatty acids attached to each molecule of glycerin. See what we did there. Suddenly cocoa butter has some new friends that all have to get along so that chocolate can temper adequately.
Tempering chocolate is essentially ordering and packing of fat crystals in the right size and number. Since Cocoa butter is so complicated, there is a range of temperatures for when it melts. But these temperatures are not the only factor that contributes to proper tempering. The rate of cooling, how much the chocolate is stirred or agitated, and the duration of time spent on the tempering process all can positively or negatively affect how stable the fat crystals are when finished.
In conclusion, when you see chocolate that has a white or grey dull look to it, you must understand that something either went wrong during the tempering process or after the fact. Most likely, if you find white chocolate from a prominent manufacturer like Nestle, Hershey, or Mars, something affected the chocolate after the fact to cause it to turn white. If you see chocolate that has turned white at your local chocolatier, it was probably a bad-tempered batch of chocolates. These are still fine to eat, and you may even get them at a discount.