Scientists have deciphered the physical process that takes place in the mouth when you eat a piece of chocolate, as it changes from a solid to a smooth emulsion that many people find totally irresistible.
By analyzing each of the steps, the interdisciplinary research team at the University of Leeds hopes it will lead to the development of a new generation of luxury chocolates that will have the same feel and texture, but will be healthier to consume. During the moments when it is in the mouth, the sensation of chocolate arises from the way the chocolate is lubricated , either by the ingredients in the chocolate itself or by saliva or a combination of both.
Fat plays a key role almost immediately when a piece of chocolate comes into contact with the tongue . After that, the solid cocoa particles are released and become important in terms of the tactile sensation , so the fat deeper within the chocolate plays a fairly limited role and could be reduced without having an impact on the feel of the chocolate.
Anwesha Sarkar, professor of colloids and surfaces at Leeds School of Food and Nutrition Sciences, said: “Lubrication science provides mechanistic information about how food actually feels in the mouth. You can use that knowledge to design foods with better taste, texture or health benefits.”
“If a chocolate has 5% fat or 50% fat, droplets still form in your mouth and that gives you the sensation of chocolate. However, it is the location of the fat in the chocolate composition that matters at each stage of lubrication, and that has rarely been investigated.”
"We are showing that the fat layer should be on the outer layer of the chocolate, this is the most important thing, followed by an effective coating of the cocoa particles with fat, which helps make the chocolate feel so good."
The study, published in the scientific journal ACS Applied Materials and Interface , did not investigate the question of chocolate taste . Instead, research focused on its feel and texture .
The tests were carried out 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, which included in situ imaging . Tribology is about how surfaces and fluids interact, the levels of friction between them, and the role of lubrication: in this case, saliva or chocolate liquids. All of those mechanisms are happening in your mouth when you eat chocolate.
When chocolate is in contact with the tongue, it releases a fatty film that covers the tongue and other surfaces of the mouth. It is this fatty film that makes the chocolate feel soft the entire time it is in your mouth.
Dr Siavash Soltanahmadi, from the Leeds School of Food Sciences and Nutrition and lead researcher on the study, said: "By understanding the physical mechanisms that occur when people eat chocolate, we believe a next generation of chocolate that offers the touch and feel of high-fat chocolate but is a healthier option.” “Our research opens up the possibility that manufacturers can intelligently design dark chocolate to reduce the total fat content.”
“We believe that dark chocolate can be produced in a gradient layer architecture with fat covering the surface of the chocolates and particles to deliver the sought-after indulgent experience without adding too much fat within the body of the chocolate.”
Chocolate sales revenue in the UK is expected to grow over the next five years, according to research from business intelligence agency MINTEL. Sales are expected to grow by 13% between 2022 and 2027 to reach £6.6bn.
The researchers believe that the physical techniques used in the study could be applied to the investigation of other foods that undergo a phase change, where a substance transforms from solid to liquid, such as ice cream, margarine or cheese.
This project received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme.
