Good chocolate is a cool art

It's a tough job, but someone's got to do it, and researchers in the UK have bravely set out to discover what makes chocolate taste so good.

Although the origins of chocolate can be traced back to the ancient Maya and Aztec civilisations in south America most people have been too busy eating the stuff to work out the secret of the taste.

Not everyone likes chocolate this much

But now Professor Kevin Robert from Heriot-Watt University at Edinburgh in Scotland has been investigating the secret of perfect chocolate.

"The cocoa fat, that's the fat that comes out of the cocoa bean, is responsible for the snappy feeling you get from a bar of chocolate," he said.

But it is not quite that simple. "It's due to the way that the material crystallises. It forms a crystal in a same way that gem stones are crystal," said Prof Robert.

To see the cocoa crystals, the researchers irradiated cooling cocoa butter with X-rays and measured the way they bounced off atoms in the crystals.

The different crystalline forms scatter the X-rays in distinctive patterns. The researchers were able to work out the precise temperatures at which they appear and disappear.

Kevin Robert's team used a machine called a synchrotron to produce a very bright beam of X-rays.

Chocolate must be made and stored with care

"Synchrotron radiation is X-rays, X-rays like you might use to have an X-ray in a hospital, but we use it to probe through the chocolate and examine the fat component in chocolate as it forms into solid," he said.

"We vary the processing conditions used to make the chocolate and we see what happens to the molecules and how they fit together."

The scientists hope their research will allow manufacturers to perfect the traditional method of making chocolate, which is inherently risky.

To make chocolate the cocoa butter is first cooled below the melting point to crystallise it very fast, then it is reheated to the temperature at which the fat melts.

But small differences in cooling temperature can create big differences in the taste of the chocolate. If the makers get it wrong, Professor Robert says the results can be quite unpleasant.

"Basically, if you put the fat into your mouth, instead of melting in your mouth and all the nice cocoa disgorging itself on to your tongue, and you saying 'Oh, this is a nice bar of chocolate!' what actually happens is it just sits there for a while, and you feel it is rather horrible - it's all rather waxy."