Ever since the Spaniards brought home the cocoa beans from South America in the early 16th century, chocolates have been a delicacy the worldover. The question of what exactly makes chocolates taste so irresistibly delicious has baffled scientists for years. Researchers at the University of Leeds in the United Kingdom now believe they have the answer to this age-old enigma.
Food scientists and technologists regularly use lubrication science — which provides mechanistic insights into how food actually feels in the mouth — to design food with better taste, texture or health benefits. Researchers at Leeds leveraged data from lubrication science to decode the physical process that takes place when a piece of chocolate is eaten.
Following analysis of each of the steps involved, as the solid chocolate bar undergoes transformation to a smooth emulsion in the mouth, the researchers concluded that the delectable chocolaty taste was the outcome of how chocolates are lubricated in the mouth. They noted that this lubrication comes from ingredients within the chocolate itself, or from saliva, or a combination of both processes.
The study found that when a piece of chocolate comes in contact with the tongue, fats present on the chocolate surface form droplets in the mouth that provide a large part of the chocolate sensation. It is only in the next stage that solid cocoa particles inside the chocolate are released to provide the tactile sensation of chocolates. Fats that are present deeper inside the chocolate were found to play only a rather limited role in the taste sensation. In other words, whether a chocolate has 5 percent fat or 50 percent fat is less relevant than where this fat is located in the make-up of the chocolate.
Tests were conducted using a luxury brand of dark chocolate on an artificial 3D tongue-like surface that was designed at the University of Leeds. The researchers used analytical techniques from a field of engineering called tribology to conduct the study. Tribology is about how surfaces and fluids interact, the levels of friction between them and the role of lubrication: in this case, saliva or liquids from the chocolate. Those mechanisms are all happening in the mouth when chocolate is eaten.
The study concluded that when chocolate is in contact with the tongue, it releases a fatty film that coats the tongue and other surfaces in the mouth. It is this fatty film that makes the chocolate feel smooth throughout the entire time it is in the mouth. What this proves is that in order to receive the incredible chocolate sensation in the mouth, the fat layer needs to be on the outer layer of the chocolate, followed by an effective coating of the cocoa particles below the fat layer.
“We believe exquisite dark chocolate can be produced in a gradient-layered architecture with fat covering the surface of chocolates and the cocoa particles to offer the sought after self-indulging experience without adding too much fat inside the body of the chocolate,” said the researchers.
They added that the physical techniques used in the study could be applied to the investigation of other foodstuffs that undergo a phase change, where a substance is transformed from a solid to a liquid, such as in ice-cream, margarine or cheese.