Large deformation and crystallisation properties of process optimised cocoa butter emulsions

di Bari, Vincenzo (2015). Large deformation and crystallisation properties of process optimised cocoa butter emulsions. University of Birmingham. Ph.D.

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Abstract

The objectives of the research presented in this thesis were: (1) optimise the processing conditions for the production of water-in-cocoa butter emulsions; (2) understand the role of water droplets on the large deformation behaviour and crystallisation properties of emulsified systems. Results showed that a scraped surface heat exchanger could be used to produce tempered emulsions with a small average droplet size (~3 µm). In all systems stability was provided by the emulsifier and fat crystals forming a network both in the bulk and at the interface of the water droplets.

Characterisation of the large deformation properties of emulsions showed that the elastic behaviour remained constant at low aqueous phase percentages while the strength at fracture decreased. This result suggests that water droplets act as stress-concentrator elements, which is probably due to their partial sintering with the bulk network.

Results of crystallisation experiments have shown that the effect of droplets on kinetics of crystallisation depends on the degree of supercooling: only at relatively high temperatures (15, 20 °C) the dispersed droplets increased the kinetics of crystallisation compared to bulk cocoa butter (CB). With respect to polymorphic evolution, emulsified systems evolved faster toward more stable forms than bulk CB at all temperatures.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):