The irresistible melt-in-the-mouth sensation of chocolate, according to scientists, comes down to the way it lubricates the tongue.
One study examined the physical process by which a firm square of chocolate turns into a smooth emulsion. It found that chocolate releases a fatty film that coats the tongue and provides a soft feel the entire time it is in the mouth.
Dr. Siavash Soltanahmadi, the study’s lead researcher at the University of Leeds, said the findings could be used to design low-fat chocolate that mimics the sensation of a high-fat product.
“We believe that a next generation of chocolate can be developed that offers the feel and sensation of high-fat chocolate while still being a healthier choice,” she said.
Soltanahmadi and colleagues set out to create a texture sensation using a luxury brand of dark chocolate and an artificial tongue. The device has a 3D printed tongue-like texture, held at 37C (98.6F) and powered to move like a human tongue.
They found that shortly after the chocolate is put in the mouth, the tongue becomes coated with a layer of fat, which depends on the fat content of the chocolate. After that, solid cocoa particles are released that become important for the tactile sensation, the researchers discovered.
“We show that the fat layer should be on the outer layer of the chocolate, this is most important, followed by effective coating of the cocoa particles by fat, these help chocolate feel so good,” she said.
This means that the fat deeper in the chocolate plays a limited role in contributing to sensation and can be reduced without affecting how the chocolate feels in the mouth. The researchers suggested that chocolate bars with a fat content gradient or a low-fat bar coated in high-fat chocolate might work well as a healthier alternative.
Soltanahmadi said creating healthier chocolate was a challenge for the food industry because low-fat versions weren’t always as tasty.
“Our research opens up the possibility that manufacturers could intelligently design dark chocolate to reduce the overall fat content,” she said. “We believe that dark chocolate can be produced in a gradient layer architecture where fat coats the surface of chocolates and particles to provide the sought-after self-indulgence experience without adding too much fat into the body of the chocolate.”
The researchers suggested that similar techniques could be applied to design healthier versions of other foods that change from a solid to a liquid in the mouth, such as ice cream or cheese. The findings are published in the journal ACS applied materials and interfaces.