An examination of the inter-relationship between structure and kinetics associated with crystallisation of single and mixed chocolate confectionary fats
A detailed examination of the crystallisation and subsequent phase transformation of confectionery fats was carried out. The systems studied were: tripalmitin/triacetin; tripalmitin/cocoa butter; tripalmitin/triolein; milk fat/cocoa butter and milk fat/cocoa butter/yn (synthetic lecithin). Three different techniques were used to investigate these systems, i.e. small angle and wide X-ray scattering, nucleation (slowcool and crashcool). Tripalmitin showed a very low solubility in triacetin and hence it did not follow the behaviour of an ideal solution. Whereas the system tripalmitin/triolein showed an ideal behaviour. In the case of the tripalmitin and cocoa butter mixtures the ideal behaviour was observed only for high concentrations of tripamitin. It was observed that for the milk fat/cocoa butter mixtures two crystallisation and dissolution processes took place depending on the concentration. This result was confirmed by the SAXS experiments. During the small angle X-ray scattering studies of tripalmitin and cocoa butter system it was observed that Form I showed a higher stability than that reported in literature. Measurements of the induction time under well-controlled mixing conditions for the binary mixtures tripalmitin/cocoa butter and milk fat/cocoa butter were carried out using a new crash cool tempering cell. It was found that the induction time decreases as the shear rate increases. As a part of this work a new variable temperature variable shear processing cell was developed in order to study in-situ the crystallisation process under conditions which are more representative of the industrial process. The effects of shearing, time and temperature on the formation of polymorphic forms of cocoa butter and a mixture of fats were examined. For both systems, the shear and temperature had the effect to vary the induction time of crystallisation of Form V.