Another thing we learned about chocolate this week, is that is can bloom. In fact, we found some blooming, right in our own cupboard. See the white film on the baker's chocolate below? It's called fat bloom, and is caused when chocolate has been stored at temperatures above 75 degrees Fahrenheit, allowing the cocoa butter to separate from the solids, and rise to the surface of the bar.
If you rub fat bloom, it will feel greasy, and will melt, or appear to rub off. The magnified picture below on the left is of the chocolate before it was touched, and the picture on the right is after the bloom was wiped off. If I understand correctly, the light brown spots are the cocoa butter.
We tried to produce this same kind of bloom on some of our chocolate coins by melting them, and then allowing them to cool overnight.
Our results were less than impressive, until we melted the chocolate again, stuck it in the freezer to harden, and then let it sit out on the counter. Our chocolate bloomed alright...
...this time with a sugar bloom.
Sugar bloom occurs when chocolate is stored in a humid environment, or when it "sweats" as it is brought from a cold storage, such as the freezer, into a warm room. Condensation beads on the surface of the chocolate, and draws out the sugar. When the water evaporates the sugar is left crystallized on the surface of the chocolate.
It appears grainy, and can't be rubbed off...
...and is incredibly interesting to view through a handheld microscope. You took my advice last year, and picked one of those up, right?
According to the labeling on our box of baker's chocolate, blooming does not hurt the taste or quality of the chocolate. There are many who disagree, and advise against using bloomed chocolate. My children however, found it to be just fine, except for the baker's chocolate - which of course, I let them taste, too :).
For an excellent, but easy to understand, scientific explanation chocolate bloom, as well as a great diagrammed explanation of the purpose of emulsifiers in chocolate, check out this post from Bite-Sized Biology.
It's great to be a homeschooler.