What makes chocolate so irresistible?

Scientists from the University of Leeds have now unravelled the mystery behind what happens when the chocolate melts in your mouth. (Image for representation)
| Photo Credit: Reuters

The sweet and rich taste of chocolate is a sensorial treat that many enjoy, but is that all that makes the sweet irresistible?

Scientists from the University of Leeds have now unravelled the mystery behind what happens when the chocolate melts in your mouth.

While studying the gradual dissolvement of chocolate chunks, scientists found that the sensation of chocolate melting on your tongue comes from the lubrication provided by saliva when it dissolves the sugar particles, or from ingredients used to make the chocolate.

Published in ACS Applied Materials and Interfaces, the study saw researchers focusing on the texture and feel of chocolate rather than its taste. They used techniques employed in tribology— the study of friction, lubrication and interaction between surfaces— to test a luxury brand chocolate on an artificial tongue-like structure. Four different samples of dark chocolate were used.

Analysing the different stages of chocolate sensation, from first contact with tongue to mixing with saliva, scientists found that a fatty layer of film covers the tongue and the mouth. The smoothness provided by the film between the surface of the mouth and chocolate is what gives the rich, melt-in-your-mouth sensation.

“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,” Anwesha Sarkar, study co-author and a professor at the University of Leeds, said in a press release.

She pointed out that the location of the fat matters more than the amount of fat. “If a chocolate has 5% fat or 50% fat it will still form droplets in the mouth and that gives you the chocolate sensation. However, it is the location of the fat in the make-up of the chocolate which matters in each stage of lubrication, and that has been rarely researched.”

Though there have been numerous studies on the oral perception of chocolate when bitten into, however, the perception of chocolate when licked has not been adequately explored.

The melt-in-your-mouth property of chocolate also depends on a number of factors such as the concentration of its constituents, size and shape of solid particles such as sugar crystals and cocoa solids and the amount of emulsifier. These factors affect the flow characteristics, primary taste perception and behaviour of chocolate in the mouth.

Studying edible phase change materials (PCMs) such as chocolate can be extremely beneficial as it can help design healthier food as well as engineer food for vulnerable populations. The new study opens up many avenues for food science and engineering as understanding the physical mechanics behind what makes food taste good can help provide healthier options while retaining qualities that make it palatable. These results can also be used to study other food items that transform from solid to liquid, such as ice cream, margarine and cheese.

Siavash Soltanahmadi, the lead researcher, said that the research opened up the possibility that manufacturers could intelligently design dark chocolate to reduce overall fat content.

“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,” he said.