It is all down to lubrication
From: University of Leeds
January 13, 2023 -- 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 into a smooth emulsion that many
people find totally irresistible.
By analyzing each of
the steps, the interdisciplinary research team 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.
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.
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