Dutch scientists have adopted novel 3D printing techniques to design and construct the perfect chocolate structure for pleasurable ‘crackliness’.
According to the team from the University of Amsterdam, Delft University, and Unilever, they have successfully demonstrated the mouthfeel—and even the crackling sound that the best chocolate make when we bite into it—by designing this notoriously difficult material in the same way one would a metamaterial.
It is no secret that chocolate is not an easy material to work with. Just ask any professional baker or chocolatier: controlling cocoa butter’s crystal structures and emulsions either by heating or cooling is the key to good chocolate.
Cocoa butter is a six-phase polymorphic crystal and its ‘Phase V’ is the most desirable; it crackles and melts rather than crumbling, and gives high-end chocolates their delectably glossy sheen.
But this can be time-consuming and it takes weeks for a piece of properly-tempered chocolate to crystallize completely.
The bad news is that phase V crystals are unstable and they tend to degrade into dull phase IV crystals over time, making chocolate less crackling to say the least.
The first challenge for the Unilever and Dutch scientists was to get their building material under control.
They did this by very carefully heating it up, adding some cold chocolate, cooling it down again, and then putting it in a 3D printer.
This allowed them to print essentially any shape of chocolate material they wanted, while guaranteeing that the base material always had the same properties.
The first shape of edible material that the scientists experimented with was an S-shaped chocolate with many twists.
The goal was to test how this material would break and how that breaking would be experienced in the mouth.
Not surprisingly, the breaking properties depended strongly on the direction of ‘biting’, note the scientists.
When the chocolate was pressed from above, many different cracks occurred one after another, but when pressed in the direction perpendicular to the picture (see above), usually only a single crack occurred.
According to the scientists, spiral-shaped chocolate metamaterials have quite interesting and tunable properties.
Not only does the number of windings directly control the number of cracks when the material is pressed mechanically; the test panel could also clearly distinguish between less and more cracks when eating the chocolates.
Moreover, sound recordings showed that the sound the chocolates make when being bitten reflects the number of cracks, adding to an enjoyable eating experience.
Image and content: University of Amsterdam
