The irresistible melt-in-the-mouth sensation of chocolate comes down to the way it lubricates the tongue, according to scientists.
A study investigated the physical process by which a solid square of chocolate morphs into a smooth emulsion. It found that chocolate released a fatty film that coats the tongue, giving a smooth sensation for 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 mimicked 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 yet is a healthier choice,” she said.
Soltanahmadi and colleagues set out to investigate texture sensation using a luxury brand of dark chocolate and an artificial tongue. The device has a 3D-printed tongue-like texture, is kept at 37C (98.6F) and powered to move like a human tongue.
They found that soon after the chocolate is placed in the mouth, the tongue becomes coated in a fatty layer, which depends on the fat content of the chocolate. After that, solid cocoa particles are released and they become important in terms of the tactile sensation, the researchers found.
“We are showing that the fat layer needs to be on the outer layer of the chocolate, this matters the most, followed by effective coating of the cocoa particles by fat, these help to make chocolate feel so good,” she said.
This implies that the fat deeper inside the chocolate plays a limited role in contributing to sensation and could be reduced without having an impact on how the chocolate feels in the mouth. The researchers suggested 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 were not always as appetising.
“Our research opens the possibility that manufacturers can intelligently design dark chocolate to reduce the overall fat content,” she said. “We believe dark chocolate can be produced in a gradient-layered architecture with fat covering the surface of chocolates and particles to offer the sought after self-indulging experience without adding too much fat inside the body of the chocolate.”
The researchers suggested similar techniques could be applied to help design healthier versions of other foods that transform 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 & Interfaces.