A clever design can significantly increase the enjoyment of food, physicists have shown.

Chocolate: most people like it porridge. However, the fact that we can enjoy a large piece of chocolate in this way is not only due to the taste. The mouthfeel also plays a role. And in a new study – published in the journal Soft Matters – Dutch scientists now show that it is possible to design and perfect the mouthfeel of an edible substance – in this case chocolate. The result is in fact a perfect piece of chocolate that provides even more eating pleasure.

metamaterial

The special chocolate is actually a meta-material. This is a material with exceptional properties that does not occur in nature, but is designed by humans. “Metamaterials, for example, can be very light and at the same time very strong,” says researcher Corentin Coulais. It is well known that such materials have enormous potential. However, this often refers to applications in the field of engineering (the construction of systems or structures, for example). What has never really been thought about, however, is how metamaterials can also come in handy in the food industry. “And we have now taken a first step,” said Coulais. “By creating metamaterials, made from chocolate, that can break in extraordinary ways.”

Breaking is nice

The researchers had a clear goal in mind: to improve the mouthfeel of chocolate. Because when it comes to that mouthfeel, there is one thing that people really enjoy and that is crunchy food. The more often the food breaks in the mouth, the better. And so the researchers set to work with that premise. They made good use of a 3D printer. This allowed them to give the chocolate any shape they wanted.

Challenges

Incidentally, that certainly does not mean that the search for a chocolate with the ultimate mouthfeel was a completed race. For example, the researchers first had to get their building material – the chocolate – under control. And as ardent supporters of Heel Holland Bakt know, that is still a challenge for even the better amateur bakers, let alone for physicists. But there were still more hurdles to overcome, according to researcher Corentin Coulais. “Finding the right shape that can be both printed and has a big effect on mouthfeel was the biggest challenge.”

But that also worked. And the first chocolate that came out of the printer as part of this study was one with a hefty line of S-curves (see image below). Using real subjects and mechanical tests, the researchers investigated how this chocolate broke in the mouth and what mouthfeel it evoked. Not surprisingly, this turned out to be highly dependent on the bite direction. If someone put the chocolate in their mouth as in the picture below, there were a lot of fractures and therefore a lot of eating pleasure. But if someone twisted the chocolate, there was only one break (and it wasn’t that easy to bite into pieces).

spirals

“Our initial results show that chocolate metamaterials provide a unique and enhanced sensory experience,” said Coulais. But could it be better? The researchers thought so and went on the hunt for a shape or structure in which the number of breaks in the material could be ‘programmed’. In other words: shapes that are doomed to disintegrate into many pieces in the mouth. They soon arrived – again through experiments – with spiral-shaped pieces of chocolate (see image below). Test subjects appeared to appreciate the pieces of chocolate more especially if they had multiple convolutions. This not only resulted in more fractures, but also in a slightly different sound than if the piece of chocolate had only one turn, for example. And both the mouthfeel of those multiple convolutions and the sound associated with the occurrence of multiple fractures enhanced the eating pleasure.

Design without trying out

And that’s how the researchers designed by trial and error thus different chocolate textures accompanied by different mouthfeels. A rather labour-intensive process. And so they wondered if there was another way. Should designing a pleasant dining experience be a matter of trial and error? Or was it also possible to design and optimize the ultimate chocolate before it is made? Yes, as the researchers show, with a cleverly chosen mathematical model. “Physics or mathematics can be used to calculate and design how the material breaks,” explains Coulais. “We used a specially designed algorithm for this. This complex algorithm optimizes the geometry so that the structure is stiff in one direction and soft in the other. And for that, the algorithm determines where the chocolate should be placed.” For example, the resistance to breaking can also be adjusted for different bite directions.

Armed with this algorithm, it is thus possible to design a chocolate that – at least when it comes to mouthfeel – offers the ultimate dining experience. But that is not the ultimate goal as far as the researchers are concerned. For example, comparable studies could also be conducted on other edible metamaterials where – in contrast to chocolate – there is still much to be gained when it comes to the eating experience. “Consider sustainable food, for example, such as alternatives to meat.” But people with eating disorders may also benefit from the research in the long run. You can think in particular of people with the eating disorder ARFID, who eat very little or very selectively, because a large part of the food has an unpleasant structure or unpleasant mouthfeel for them.