It is all down to lubrication
University of Leeds
By analysing each of the steps, the interdisciplinary research
team at the University of Leeds hope 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 it is in the mouth, the chocolate sensation
arises from the way the chocolate is lubricated, either from ingredients in the
chocolate itself or from saliva or a combination of the two.
Fat plays a key function almost immediately when a piece of
chocolate is in contact with the tongue. After that, solid cocoa particles are
released and they become important in terms of the tactile sensation, so fat
deeper inside the chocolate plays a rather limited role and could be reduced
without having an impact on the feel or sensation of chocolate.
Anwesha Sarkar, Professor of Colloids and Surfaces in the School of Food Science and Nutrition at Leeds, said: "Lubrication science gives mechanistic insights into how food actually feels in the mouth. You can use that knowledge to design food with better taste, texture or health benefits.
"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.
"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."
The study -- published in the scientific journal ACS
Applied Materials and Interface -- did not investigate the question of
how chocolate tastes. Instead, the investigation focused on its feel and
texture.
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 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.
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.
Dr Siavash Soltanahmadi, from the School of Food Science and
Nutrition at Leeds and the lead researcher in the study, said: "With the
understanding of the physical mechanisms that happen as people eat chocolate,
we believe that a next generation of chocolate can be developed that offers the
feel and sensation of high-fat chocolate yet is a healthier choice.
"Our research opens the possibility that manufacturers can
intelligently design dark chocolate to reduce the 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."
Revenue from chocolate sales in the UK is forecast to grow over
the next five years, according to research from the business intelligence
agency MINTEL. Sales are expected to grow 13% between 2022 and 2027 to reach
£6.6 billion.
The researchers believe 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 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.
