Material experts make ‘meta chocolate’

Finely rolling, heating up, congealing, evaporating. Expert chocolatiers have plenty of tricks up their sleeves to get the best out of cocoa beans. Few other foodstuffs require so much dedication and technological ingenuity. But then, you do get a delicious product. Chocolate with a good bite, that melts in the mouth, and quickly releases countless flavours.

But it could always be better. Last month in the scientific magazine Soft Matter, researchers at the University of Amsterdam, TU Delft and Unilever described a technique to use 3D printers to print pieces of chocolate that was even more pleasantly crunchy. They did this by building the confectionary from tiny spiral and S shaped structures. Read the details in their article entitled Edible mechanical metamaterials with designed fracture for mouthfeel control. By playing around with the shape, the researchers could determine how the chocolate would break up in the mouth.

Chocolate and crispy space carrots
Playing with the mouthfeel. This is what the researchers are doing. “We believe that in the future, 3D printers will be able to produce anything,” says co-author of the study, Materials Expert Alejandro Aragón of the Faculty 3mE. “Using carrot powder, you should be able to add water and print carrots that have a comparable texture as the real vegetable.” Very handy for astronauts in space.

This type of computer controlled space snacks still sounds a long way off. As do more things that metamaterials have in store. Metamaterials are materials that have exceptional qualities derived from repeating patterns at micro or nano scale. The special chocolate is also a metamaterial.

‘This is a whole new area in the food industry’

Metamaterials are by definition synthetic. They often have unusual electromagnetic qualities such as a negative refraction index that allows them to bend slightly. In theory, you could use metamaterials to make an invisibility cape, like the one Harry Potter has. They can be exceptionally light and strong at the same time. They are usually designed for high tech applications and for fundamental research in the field of materials science. “This is a whole new area in the food industry,” says Aragón.

Aragón developed computational tools that cab predict the fracture behaviour in a metamaterial. “We developed advanced finite element techniques for the analysis and optimization of chocolate unit cells. These techniques are also very general and therefore could be applied to the design of other (meta)materials and structures.”

Bad luck for chocolatiers. The manufacturing of chocolate was already so complicated. Chocolate consists mostly of cocoa butter. This is a mixture of fats and triglycerides. Oddly enough, these triglycerides can crystallise in six different ways. Each crystal is designated a Roman numeral. Chocolate producers have done their best to create chocolate with the V crystal type. This crystal melts at just under 37°C, is shiny, firm, and has good breaking qualities. But it does not stop here. Maybe patissiers should also familiarise themselves with chocolate metamaterials.