Ever left a chocolate bar long enough for it to turn white? While it's harmless, the sweet stuff doesn't look that appetising after it happens. Scientists at Nestle have started work to figure out what's going on at a microscopic level by X-raying chocolate.

One thing you immediately notice, chocolate has a lot of complex chemistry to it. Cocoa butter in chocolate can form one of six different crystal structures, one of which creates the smooth, glossy chocolate look and feel that is loved by all. However, if the chocolate is heated up then cooled in a process called tempering, this could make one of the other five. One of which, through improper tempering, will leave fat blooms behind, which makes the white film on chocolate.

These fat blooms occur because of a loss of specific crystal structure, leaving the fat free of crystallisation and mitigating to the surface. How this happens has been a mystery...until now.

After X-raying a powdered mixture of cocoa, sugar, milk, powder and cocoa butter (the powder speeds up the process of tempering and forming crystal structures), they ran liquid oil through the mix to dissolve the solid cocoa butter, losing the crystal structure and the fat blooming we all know. Essentially, the cocoa butter keeps all the chemicals together in their crystal structures, and when affected in some way, you can see differences.

The researchers concluded that the more porous (resistive to the elements) the chocolate is, the more prone it is to blooming, so think more the larger chocolate bars and you should be more safe. Also keep it cool to maintain crystal structure. I know I'm probably the only person to keep chocolate in the fridge, but it's recommended now.

Science!