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Title: Geometrical and material effects on sensory properties of confectionery wafers and similar extruded products
Author: Butt, Saba Sohail
ISNI:       0000 0004 6423 5271
Awarding Body: Imperial College London
Current Institution: Imperial College London
Date of Award: 2017
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The aim of this research is to determine if products made via the two cooking processes named are producing materials with similar properties thus resulting in a similar consumer perception or whether two fundamentally different products are being obtained. The presented work investigates the correlations between mechanical behaviour, fracture response, microstructure, acoustic emissions and sensory evaluation of a wide range of products made via the extrusion and baking processes. The internal microstructure of the products was examined with a Scanning electron Microscope (SEM). A notable difference between the distributions of the cells was observed between the two products; the wafer comprised of separate skin and core regions with variable pore sizes whereas a more uniform distribution of the pores was present in the extruded products. The mechanical behaviour of both, the extruded and baked, products was characteristic of brittle foam. The extruded products were all found to be stiffer materials in compression when compared to the baked wafers and the extruded products were found to be less anisotropic when compared to baked wafers. Analytical models were used to determine the actual mechanical properties of baked wafer and it was concluded that taking the geometry of the baked wafer into account was essential in finding accurate properties. Sensory, acoustic and mechanical testing results were successfully compared to draw links between the structure-property-texture of the different food products. X-ray Micro tomography (XRT) was used to attain a stack of image slices of the extruded tube architecture which was used to create Finite Element (FE) model of the product volume. Representative Volume Element study was conducted and the ‘crushable foam’ material model was implemented on the FE model to study the microstructure behaviour under compressive loading. The model of the complex architecture was able to predict the deformation behaviour of the extruded product. For future study, the FE models can be used to modify the microstructure to perform parametric studies to quantify the effect of individual geometric variables i.e. pore diameter, on the global response.
Supervisor: Charalambides, Maria ; Williams, Gordon Sponsor: Nestle PTC ; Biotechnology and Biological Sciences Research Council
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral