Scientists create ‘chameleon rainbow’ chocolate

The rainbow chocolate employs the same surface imprint structure as chameleons. ETH Zurich / Giulia Marthaler

Swiss scientists have discovered how to make chocolate bars shimmer like rainbows when reflected in light, by imprinting a special structure on the surface of the confectionery. 

This content was published on December 19, 2019 - 15:55

The shimmering effect has been perfected without the use of artificial additives by researchers at Zurich’s Federal Institute of Technology (ETHZ) and the University of Applied Sciences and Arts Northwestern Switzerland.

Changing the surface structure of the chocolate with a “surface imprint” makes it shimmer with what scientists call “structural colour”.

“The process is similar to a chameleon, whose skin surface modulates and disperses light to display specific colours,” according to a ETHZ press release.

The project was initially driven by “sheer curiosity” as two scientists converted coffee room chat into a practical experiment. They started out with the edible coatings of gold and titanium oxide but switched to changing the surface structure of the chocolate after deciding that their original idea would not make commercial sense.

Having hit upon the perfect solution, the scientists are in discussions with major chocolate producers to scale up their invention on an industrial scale and plan to establish a spin-​off company soon.

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