When Wilhelm Conrad Roentgen first stumbled upon X-rays in his laboratory at Wuerzburg University in Germany back in 1895, he probably never imagined that his revolutionary technology, used for decades to glimpse the inner workings of the body, would one day be used on chocolate.

But here we are, over one hundred years later, and scientists from the Hamburg University of Technology (TUHH) have been hard at work using x-rays to solve the vexing issue of fat blooms in chocolate.

What is a fat bloom, you ask? A fat bloom is the term used for that unappetizing layer of whitish crust that can form on chocolate.

"This can happen when liquid chocolate cools down in an uncontrolled manner and unstable crystals form, for example," explains Svenja Reinke, a researcher at TUHH.  "Despite this well-known quality issue, comparatively little has been known until now about its root causes." 

When you see fat bloom on chocolate, one's first response is to deem the sweet out of date. That's because fat bloom is the result of liquid fats within the chocolate, such as cocoa butter, migrating to the surface. And this usually happens when the chocolate has been stored for long periods amidst warm temperatures.

And although fat bloom is perfectly harmless, it is a thorn in the side of cholate makers around the globe.

"Even though fat bloom does not actually constitute any deterioration in the quality of the product, the visual alteration associated with it can lead to a large number of consumer complaints," points out Prof. Dr.-Ing. Stefan Palzer, from the food company Nestlé. "This is why fat bloom continues to be one of the most important quality defects in the confectionary industry."

So the sweet-toothed researchers at TUHH have teamed up with the Deutsches Elektronen-Synchrotron (DESY) and the folks from Nestle, to explore just what causes a fat bloom. And it turns out x-rays have helped them solve the puzzle.

The team utilized DESY's x-ray source PETRA III to track the migration of fats through the chocolate in real time. The chocolates were ground to a fine powder and the x-rays were directed through them.

"The technology used to examine the samples shows us both the fat crystals and the pores inside the product, down to a scale of a few nanometres," explains Prof. Dr.-Ing. Stefan Heinrich from TUHH, who lead the investigation.

And the result of their chocolate-zapping?

"For the first time, we have been able to track in detail the dynamic mechanisms that lead to the creation of fat bloom," explains DESY scientist Dr. Stephan Roth, head of the P03 beamline at PETRA III, where the experiments were conducted. 

By reducing the porosity of the chocolate, limiting the amount of fat, and controlling storage temperatures, chocolate makers may be able to avoid unsightly fat blooms in the future.

"The experiments that have been conducted allow us as manufacturers of quality chocolate to draw conclusions concerning the root causes of lipid migration leading to blooming," points out Palzer. "These findings provide a solid foundation for developing suitable methods for avoiding one of the most important quality defects in the food industry."

I'm sure chocolate-lovers everywhere will sleep better tonight.