Shimmering chocolate may sound like a thing of dreams, but thanks to physics it is in fact a reality. Several groups have tempered their way to this magical food heaven (which is 100 percent edible), from researchers in Switzerland to a food-experimenting internet security mogul. But how do you make this treat look as good as it tastes?
As Samy Kamkar, founder of internet security firm Openpath who shared his iridescent chocolate on Twitter earlier this month, explained to The New York Times the proof is in the pudding itself. “Anyone can do this at home,” he said. “There’s no coating. There’s no special ingredient. It’s the surface texture of the chocolate itself that’s producing it.”
The first step Kamkar carried out was to temper the chocolate. By melting and cooling the chocolate, its crystals can break down and then re-form into structures that optimize its smoothness and shininess. Kamkar then placed the chocolate in a vacuum chamber to stop air bubbles forming (although he explained that this may not have been a necessary step).
So far, no rainbow, but here is where the physics comes in. Kamkar laser-cut a 3D mushroom-shaped mold with a microscopic saw-tooth wave pattern, which became imprinted onto the surface of the chocolate when it was poured inside. The trick was not the mushroom shape, but rather the grooved chocolate surface that is in fact a diffraction grating.
When white light hits a boundary similar in size to its wavelength (to the order of a hundred nanometers), its component colors spread out (diffract) at different angles. If multiple boundaries like this are equally spaced on an object (a diffraction grating), then the diffracted paths of light will constructively interfere with one another. This intensifies the separated bands of light (“rainbow”) to the point where it becomes the dominant light that you see.
You can see this on the underside of a CD or DVD for example, as the ridges, spaced evenly on its surface, separate the colors of white light into a rainbow, or even in animals whose microscopic structures interfere with light to produce their coloration. A similar process is happening with the grooved chocolate, as its surface diffracts the incoming light to produce the shimmering iridescence.
“It’s the best tasting diffraction grating you’ll ever see,” David A. Weitz, a professor of physics and applied physics at Harvard, told the NYT.
Kamkar and Weitz are not the only people allured by the prospect of iridescent chocolate. A team of researchers from Switzerland succeeded in their mission to produce glowing chocolate – which arose from a coffee break discussion in the kitchen near to their offices. In a statement from ETH Zürich, the team’s process is ready to be scaled up for industry and are already in discussions with “major chocolate producers.”
Where can I sign up for the first batch?
[H/T: The New York Times]