The appearance of food affects its taste as much as the ingredients that go into it, but all five human senses actually play a role in how we perceive and enjoy what we eat. Chocolate is a great example, as its crunch and pops are hard to perfect when baked, but are a big part of its appeal. This has led researchers at the University of Amsterdam to try using 3D printed chocolate with a unique structure to emphasise the characteristics we already associate with high-quality chocolate, hoping to find ways to change the way the material breaks and enhance the way people come into contact with all kinds of things.
As our ability to fabricate and manipulate materials at the microscopic level improves, it opens up a world of research around metamaterials. Humans have long learned how to mix different materials to produce new materials with very specific properties. For example, it is the foundation of the science of metallurgy. But metamaterials strive to do this by changing the structure of a given material to produce improved properties or properties. One of the most interesting areas of metamaterial research is that camera lenses appear completely flat to the human eye, but are actually covered with microscopic structures that can bend light as effectively as a lens, further improving smartphone photography while potentially getting rid of cameras one day. Totally bumpy.
Camera lenses and candy bars don’t seem to have much in common, but metamaterials are just as useful to chocolate lovers as they are to photographers. There are several factors that separate good quality chocolate from the cheap stuff used to make that giant bunny you might have enjoyed last weekend. The good stuff has a glossy, glossy finish that cracks easily when bitten, with a distinct click rather than shattering in the mouth. This unique texture comes from tempering, a time-consuming but important process in which the chocolate is repeatedly melted and cooled to a specific temperature to achieve a specific stage (there are six in total, the fifth stage is ideal), forming the desired Crystal structure.
Researchers at the University of Amsterdam realized that a metamaterial approach could be used to further enhance the texture and experience of biting into premium chocolate. This is achieved by creating more snaps and breaks than a more complex structure than that produced by simply pouring melted chocolate into a mold. However, the idea didn’t replace the tempering process, which actually presented some unique challenges when the researchers turned to 3D printers to make their chocolate treats.
Melted chocolate tempered to reach the phase V crystal formation is loaded into a syringe, which must be kept at 90 degrees Fahrenheit, while the printer builds the structure layer by layer. But maintaining that temperature proved to be a challenge, requiring constant recalibration to account for the thickening of chocolate over time. Using a 3D printer with a plastic extruder is finicky enough – but trading it for tempered chocolate sounds like a real nightmare.
The results are shared in a recently published paper, “Edible mechanical metamaterials with fractures engineered for taste control,” published in the journal Soft Matter. They confirmed the researchers’ speculation that the perceived quality and enjoyment of eating chocolate could be improved by increasing the number of cracks experienced when biting into a piece through an increasingly complex S-shaped structure. The researchers also found that the experience could be improved by creating chocolate with an anisotropic structure that can alter the resistance felt during bite through the shape and pattern of shearing and breaking through forces applied in specific directions.
Will we soon see companies like Lindt or Cadbury launch metamaterial-inspired products? Probably not, but there are other interesting applications of this research to food. Using a similar manufacturing process, the texture of faux meat can be improved to make it feel more like biting real meat, or for those not interested in the traditional texture of meat, it can be changed to something completely different. It can also be used to make foods that still taste delicious (or at least fool the brain into thinking they are), but are easier for those who have problems chewing or swallowing.
