The Way Chocolate Melts

Remember last month, when I said I was planning to spend some time learning about how companies create products that appeal to our sense of touch? Well, I'm in Berlin right now after a week of doing just that. I've been conducting interviews with textile manufacturers, automakers and food scientists about enhancing tactile experiences. My favorite so far was with Nathalie Martin, leader for the Behavior and Perception Group at the Nestle Lausanne Research Center. 

Martin explained that Nestle had given her an assignment in 2009 to improve a chocolate bar without changing its recipe. One of her ideas was to create a new shape for it that would optimize its melty quality. She hypothesized that giving each piece a rounder, egg-like shape instead of a flat plane would add to the surface area that users could contact with their tongues, making it more pleasurable, and also cause a faster, more intense release of the chocolate's aroma. 

To test this theory, she measured a bunch of different mouths and found an ideal size for a single piece of chocolate. Then, she and her collaborators made a bunch of different molds about the same size in various shapes - a rectangle, a triangle, a wing, an oval, a trapezoid and an egg. She made a few trial batches with each mold and had 45 trained tasters try out the varieties. Amongst chocolate eaters, there are those of us who are biters and those of us who are suckers. In this case, she asked for all the tasters to let the chocolate melt in their mouths. No chewing.

Martin's hypothesis did pan out, but not in the way she expected. The round, egg-like shape, and the rectangle were perceived to melt the most, but that didn't exactly correlate with a more chocolatey flavor. In fact, the shapes that melted the slowest, the sail and the wing, were perceived to have a more intense aroma. After evaluating the results, the team came to believe that melting indeed helps to release the volatile compounds in a piece of chocolate, but the shape can’t perfectly conform to the mouth because there needs to be enough volume for air to freely circulate and carry those aromas to those nose.

The chocolate shapes they went with

The chocolate shapes they went with

I was in bed, tossing and turning from jetlag, when I realized Nestle had sent me home with some of its specially-shaped chocolate, which is called Caillier of Switzerland Sublim Noir. 

I was in bed, tossing and turning from jetlag, when I realized Nestle had sent me home with some of its specially-shaped chocolate, which is called Caillier of Switzerland Sublim Noir. 

Martin's field has a name: psycho-rheology. Rheology involves finding ways to measure the texture and flow of materials. To understand how we eat, its important to pick apart how our mouths alter what we consume, moving it around from side to side, chewing it with various parts of our teeth, adding saliva. The reason for the addition of the prefix “psycho” is that there’s also a big brain science element. The physical changes in food don’t always line up with our perceptions of them. 

What Martin and her team kept telling me was how much touch, when it came to food, fascinated them. Flavor is easy to figure out. Sugar makes things sweeter. Vanilla gives them a bit more complexity. But texture doesn't always make logical sense. A grain of sugar and a grain of sand in a pot of yogurt may be detected almost identically by a machine or a microscope. But to the mouth, they're entirely different. 

I learned a lot of other ways that Nestle applies science to alter our food experiences. Foods that take longer to chew actually make us feel fuller. Adding flavor notes of butter and coconut can actually make us perceive yogurt as fattier, without having to add additional thickener. And using a cooking extruder, which is what's used to make puffed cereals such as Cheerios, with ingredients for ice cream, can actually build imperceptible air bubbles, make it lighter than the real thing but just as creamy-feeling.

Today, I'm celebrating May Day (the equivalent of Labor Day in much of Europe), by taking the day off and attending a yearly street fair.


Sushma Subramanian