According to scientists, the irresistible melt-in-your-mouth sensation of chocolate is due to the way it lubricates the tongue.
A study investigated the physical process by which a solid square of chocolate turns into a fine emulsion. It was found that the chocolate releases a fatty film that covers the tongue, giving a smooth sensation the entire time it is in the mouth.
Dr Siavash Sultan Ahmadi, lead researcher on the study at the University of Leeds, said the findings could be used to design a low-fat chocolate that mimics the sensation of a high-fat product.
“We think a new generation of chocolate could be developed that gives the feel and texture of high-fat chocolate, but is a healthier option,” she said.
Sultanahmadi and colleagues set out to investigate the sensation of texture using a premium brand of dark chocolate and an artificial tongue. Featuring a 3D-printed tongue-like texture, the device is kept at 37 degrees Celsius (98.6 Fahrenheit) and is rigged to move like a human tongue.
They found that soon after the chocolate was placed in the mouth, the tongue became covered with a greasy coating, which depended on the fat content of the chocolate. Afterwards, the researchers found, the cocoa solids are released and become important in terms of sense of touch.
“We show that the layer of fat should be on the outer layer of the chocolate, and this is most important, followed by an effective coating of the cocoa particles with the fat, which helps the chocolate feel comfortable,” she said.
This means that the fats deep within the chocolate play a limited role in contributing to the sensation and can be reduced without affecting the feel of the chocolate in the mouth. The researchers suggested that chocolate bars with a graduated fat content or a low-fat bar, which are coated with high-fat chocolate, may work well as a healthy alternative.
Sultanahmadi said that making healthy chocolate was a challenge for the food industry because the low-fat varieties were not always as tasty.
“Our research opens up the possibility that manufacturers can intelligently design dark chocolate to reduce the overall fat content,” she said. “We believe that dark chocolate can be produced in a layered, graduated structure with the fat covering the surface of the chocolate and the particles to deliver the desired self-indulging experience without adding too much fat inside the body of the chocolate.”
The researchers suggested that similar techniques could be applied to help design healthy versions of other foods that go from solid to liquid in the mouth, such as ice cream or cheese. The results have been published in the journal Applied Materials and ACS Interfaces.