Question: why do you like chocolate

Lynne Thomas answered on 24 Jun 2014:

Who doesn’t like chocolate? Its that melt in the mouth feeling, the smooth taste and the feeling that the endorphins give you making you feel happy :-).

Of course far more interesting is that this is all down to the Chemistry of the chocolate. The melt-in-the-mouth feeling isn’t straight forward to get and its all down to the cocoa butter and something called polymorphism! When you make a solid of something, the atoms tend to arrange themselves in a regular three-dimensional grid a bit like a three-dimensional brick wall. This is a crystal. But it turns out that there is not just one grid that the molecules can arrange into. Imagine you are laying a driveway using bricks. You can do this two ways, the bricks are all lined up the same way (in parallel) like in a brick wall. Or alternatively, you can tilt the bricks relative to one another and make a prettier pattern called a herring-bone pattern. Both ways fill up the driveway with no gaps.

The same thing happens in crystals but the bricks are now molecules. In cocoa butter, there are actually six possible arrangements of the cocoa butter molecules into a solid. Four melt below your body temperature so would make a pretty rubbish chocolate bar as it melts when you touch it! One melts a few degrees above body temperature and one melts at your body temperature and gives you that melt-in-the-mouth sensation. The trouble is, if you left the molecules to their own devices, they would always form the highest melting point form and so it wouldn’t be so nice to eat. To make the form that we like, they have to do a process called tempering where they heat and cool and stir the chocolate in precisely the right way to get the right solid form (crystal) of cocoa butter.

If the chocolate melts afterwards and goes hard, or you leave chocolate for a long time, it tends to have a white coating on the surface – this is called blooming and this happens because the cocoa butter molecules rearrange themselves all by themselves (either by energy being put in through heating, or just over a long period of time) to make this higher melting point cocoa butter. If you eat it, it isn’t as smooth and it tastes a bit gritty (it doesn’t melt in your mouth any more). Its not bad for you but it doesn’t taste so good!