Physico-Chemical Properties of Tristearin-Oil Blends.

摘要

In order to understand how the chemical structure of liquid oil influences the crystallization process of hardstock fats, a set of binary triglycerides systems were made of either tristearin with one medium chain triglycerides (MCT) or tristearin with one unsaturated triglyceride. The system is assessed in terms of microstructure, kinetics, and phase behavior using differential scanning calorimetry (DSC), polarized light microscopy (PLM), small deformation rheology and nuclear magnetic resonance (pNMR). For unsaturated triglycerides, irrespective of the dilution factor used, the mode of nucleation remained instantaneous, while for medium chain triglycerides the mode of nucleation changed from instantaneous to sporadic when the samples were diluted beyond 70% oil. The fractal dimension results also indicated that MCTs altered the crystal microstructure of tristearin differently than unsaturated triglycerides. The solubility curve further confirmed that the unsaturated oil blends obeyed ideal solubility while MCTs oils probably co-crystalized with tristearin and did not act as a simple dilution factor. The work from this thesis provide theoretical evidence that it is possible to manipulate the structure and thus the properties of hardstock fat by incorporating different types of oils.;On the other hand, the confinement effect of the solid fat also alters the micro-viscosity of the liquid oils embedded in the oil-fat blends. The micro-viscosity of the liquid oil in the system was measured by fluorescence spectroscopy using Citrus red (CR) 2 as a luminescent molecular rotor. The viscosity decreases as the solid content of tristearin decrease but the trends did not show strong correlations. On the other hand, a strong log-logistic correlation between box-counting fractal dimension and normalized intensity of CR is observed in high-space filling colloidal fat crystal networks. Based on these results, we suggest that the use of bulk oil viscosity to predict diffusion/oil migration in multi oil phase may not be appropriate.