Summary: Researchers have decoded the sensory processing mechanisms that make eating chocolate so irresistible to most people.
Source: University of Leeds
Scientists have decoded the physical process that takes place in the mouth when a piece of chocolate is eaten, as it changes from a solid to a smooth emulsion that many people find completely irresistible.
By analyzing each of the steps, the interdisciplinary research team from the University of Leeds hope that this will lead to the development of a new generation of luxury chocolates that will have the same feel and texture but be healthier to eat.
Once in the mouth, the chocolate sensation is produced by the way the chocolate is buttered, or by the ingredients in the chocolate itself, or by saliva, or a combination of the two.
Fat plays a key role almost immediately when a piece of chocolate comes into contact with the tongue. The cocoa solids are then released and become important in terms of tactile sensation, so the fats deeper in the chocolate play a fairly limited role and can be reduced without affecting the feel or feel of the chocolate.
Anvesha Sarkar, professor of colloids and surfaces in the School of Food Science and Nutrition at Leeds, said: “The science of lubrication provides mechanistic insight into how food actually feels in the mouth. You can use this knowledge to design food with better taste, texture or health benefits.
“If the chocolate has 5% or 50% fat, it will still form droplets in the mouth and that gives you the sensation of chocolate. However, it is the location of the fat within the chocolate composition that matters at each stage of greasing, and this has rarely been investigated.
“We show that the fat layer needs to be on the outer layer of the chocolate, that’s the most important, followed by effective coating of the cocoa particles with fat, they help the chocolate feel so good.”
The study – published in the scientific journal ACS Applied Materials and Interface – did not examine the question of what chocolate tastes like. Instead, the investigation focuses on its feel and texture.
The 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, which included in-situ imaging.
Tribology is about how surfaces and liquids interact, the levels of friction between them and the role of lubrication: in this case, saliva or chocolate liquids. All of these mechanisms occur in the mouth when chocolate is eaten.
When chocolate comes into contact with the tongue, it releases an oily film that coats the tongue and other surfaces in the mouth. It is this fat film that makes the chocolate smooth the entire time it is in the mouth.
Once in the mouth, the chocolate sensation is produced by the way the chocolate is buttered, or by the ingredients in the chocolate itself, or by saliva, or a combination of the two. Image is in the public domain
Dr Siavash Soltanahmadi, from the School of Food Science and Nutrition at Leeds and lead researcher on the study, said: “By understanding the physical mechanisms that occur when people eat chocolate, we believe that the next generation of chocolate can be developed that offers the feel and feel of high-fat chocolate, but is a healthier choice.
“Our research opens up the possibility that manufacturers could intelligently design dark chocolate to reduce total fat content.”
“We believe that dark chocolate can be produced in a gradient-layered architecture with fat covering the surface of the chocolates and particles to offer the indulgent experience sought without adding too much fat to the body of the chocolate.”
Chocolate sales revenue in the UK is expected to grow over the next five years, according to research by 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 can be applied to the study of other foods that undergo a phase change, where a substance transforms from a solid to a liquid, such as ice cream, margarine or cheese.
Funding: This project received funding from the European Research Council under the European Union’s Horizon 2020 research and innovation programme.
About this sensory neuroscience research news
Author: David Lewis Source: University of Leeds Contact: David Lewis – University of Leeds Image: Public domain image
Original Research: Open Access. “Insights into the Multiscale Lubrication Mechanism of Phase Change Edible Materials” by Anwesha Sarkar et al. ACS Applied Materials and Interfaces
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Summary
Insights into the multiscale lubrication mechanism of phase change edible materials
Investigating the lubrication behavior of phase change materials (PCMs) can be challenging in applications involving relative motion, e.g. sports (ice skating), food (chocolate candy), energy (thermal storage), clothing (PCM textiles) and others.
In oral tribology, a phase change often occurs in a sequence of dynamic interactions between ingested PCM and oral surfaces from the licking stage to the mixed saliva stage at contact scales spanning micro- (cellular), meso- (papillae) and macroscales.
Often, lubrication efficiency and correlations between length scales and different stages remain poorly understood due to the lack of test settings mimicking real human tissues.
Here, we bring new insights into PCM lubrication mechanisms, using dark chocolate as an example at single-papilla (meso) and whole-tongue (macro) scales covering the solid, molten, and saliva-mixed states, bringing together highly complex biomimetic oral surfaces with in situ tribomicroscopy for the first time.
Unprecedented results from this study, supported by transcending theories of lubrication, reveal how the tribological mechanism in licking shifts from solid fat-dominated lubrication (saliva-poor regime) to aqueous lubrication (saliva-dominated regime), the latter leading to increasing the coefficient of friction by at least threefold.
At the mesoscale, the governing mechanisms were cocoa butter binding between enclosed cocoa particles and fat coalescence of emulsion droplets for the molten and saliva-mixed states, respectively.
At the macroscale, a distinctive hydrodynamic viscous film formed at the interface governing the rate-dependent lubrication behavior demonstrates the striking importance of multiscale analyses.
New tribological insights into different phase transition stages and scales from this study will inspire the rational design of the next generation of PCMs and materials containing solid particles.
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