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Modelling of the phase change kinetics of cocoa butter in chocolate and application to confectionary manufacturing

Le Reverend, Benjamin Jean Didier (2010)
Ph.D. thesis, University of Birmingham.

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Abstract

Efforts have been devoted over the last decades towards modelling phase change kinetics of fats in chocolate. The fats in chocolate have a number of crystal forms and manufacturers must deliver a product with the right polymorph to the consumer. In this work a simplifed mathematical model was developed that clusters six polymorphs into two, namely stable and unstable, depending on their Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) characteristics. This simplification allowed the phase change kinetics to be estimated from a set of DSC experiments conducted at different cooling and heating rates. The phase change reactions were coupled with the heat transfer equation and used to model temperature profiles and concentration of polymorphs in a model geometry. The model was able to predict both the temperature profiles measured by thermocouples (\(\pm\)2\(^\circ\)C ) and the fat crystals concentration as measured using XRD (\(\pm\)10%) at various locations in a chocolate slab. The model was applied to the recently developed processes using very high cooling rates such as the FrozenCone process, to explain their capabilities to produce "good" chocolate in spite of the high cooling rates used. Such modelling was not possible with existing models, which usually deal with either heat transfer or isothermal crystallisation kinetics. The main outcomes of this work are (i) the coupling of the reactions kinetics with heat transfer which can be expanded to other processes, (ii) the novel XRD method and (iii) the application to fast cooling processes and their explanation.

Type of Work:Ph.D. thesis.
Supervisor(s):Fryer, P. J. and Bakalis, Serafim
School/Faculty:Colleges (2008 onwards) > College of Engineering & Physical Sciences
Department:School of Chemical Engineering
Subjects:TP Chemical technology
Institution:University of Birmingham
ID Code:1030
This unpublished thesis/dissertation is copyright of the author and/or third parties. The intellectual property rights of the author or third parties in respect of this work are as defined by The Copyright Designs and Patents Act 1988 or as modified by any successor legislation. Any use made of information contained in this thesis/dissertation must be in accordance with that legislation and must be properly acknowledged. Further distribution or reproduction in any format is prohibited without the permission of the copyright holder.
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