ISM 2020

•••9••• Innovationen Shimmers like chameleon Researchers print rainbow colourants on chocolate Continued from page 1 Traditional methods for colour- ing chocolate have been around for a long time. But the ETH re- searchers are able to create the rainbow effect without artificial colourants. The effect is achieved simply through a surface imprint that produces what the scientists refer to as a structural colour. The process is similar to a chameleon, whose skin surface modulates and disperses light to display spe- cific colours. The story begins in the shared corridor of a university building. The food scientist Patrick Rühs, the materials scientist Etienne Jeoffroy and the physicist Hen- ning Galinski chat about choco- late during their coffee break. Although they work in different research groups, their offices are next to each other. They wonder how it might be possible to make coloured chocolate. Experiments start in the kitchen The first experiments start in the kitchen. The chocolate project is driven by sheer curiosity. The trio of researchers start to document the properties of chocolate, to understand what is special about the material and why it is brown. First they experiment with struc- tural colours based on edible coatings of gold and titanium ox- ide. Depending on the thickness of the titanium coating, golden yellow or deep blue colours ap- pear on the dark chocolate. Even so, the researchers reject that method, as the production pro- cess would be too complex and coating the chocolate, whose melting point is 31 °C, would be tricky and time consuming. The researchers decide to change course: now they want to make an impression on the surface, rather than use a coating. The breakthrough comes with the help of the materials science stu- dent Anita Zingg, who is testing the new technique as part of her master’s project. After a few at- tempts, it works: an initial col- ourful shimmer appears on the chocolate. The scientists refine the method, and the shimmer be- comes a glow. Now the group can also draw on the support of two experts in sur- face coatings at the FHNWUniver- sity of Applied Sciences and Arts Northwestern Switzerland. Per Magnus Kristiansen and Jerome Werder are developing a mould that makes it possible to imprint more than one chocolate at a time with a structural colour. The discovery is ready to be scaled up for industry. The scientists are in discussions with major chocolate producers and plan to establish a spin-off company soon. The discovery is ready for industry. Photo: ETH Zürich / Giulia Marthaler Anzeige