| The objective of this project is to study the phase behavior of some model lipid systems through partial solubility curve and isosolid diagram. The model lipid systems were composed of high-melting fat and low-melting fat classes from various sources. In this study, three high-melting fat classes were used and they were tripalmitin sample (PPP-S), cocoa butter-stearin fraction (CB-S) and palm oil-stearin fraction PO-S). The low-melting fat classes included pure tricaprylin (CCC), canola oil (CNO), sunflower oil (SFO), lard-olein fraction (LD-O) and palm oil-olein fraction (PO-O).; The isosolid diagram was constructed by quadratic interpolating the solid fat content (SFC) of 15 model lipid systems measured by low resolution pulsed nuclear magnetic resonance (NMR). To create the solubility curve, the high-melting fat class was equilibrated in the low-melting fat class within temperature range of 25 to 62.5°C for one week. The amount of the high-melting fat class dissolved in the low-melting fat class was then determined by analyzing triacylglycerol (TAG) compositions in the liquid phase using gas chromatography (GC).; The isosolid diagrams showed that low-melting lipid containing large unsaturated TAGs, e.g., SFO and CNO, only had dilution effect on all the high-melting fats, whereas the systems containing fats with similar TAG composition and molecular structure, like PPP-S/LD-O, PPP-S/PO-O, CB-S/LD-O, CB-S/PO-O and PO-S/LD-O formed monotectic solution. As the difference in molecular structure became bigger, as in the case of PPP-S/CCC, PO-S/CCC, a separation in the solid phase occurred and eutectic behavior was observed.; The solubility curve showed that PPP-S formed an ideal solution in all of the low-melting fats except in CCC. The mixture of CB-S and LD-O or CB-S and PO-O deviated from ideality. The non-ideality illustrated closer interactions between TAGs from CB-S and those from LD-O/PO-O. Another non-ideality solution was PO-S and LD-O. The melting temperature and heat of fusion of the high-melting fats calculated from ideal solubility equation were similar to those determined by Differential Scanning Calorimetry (DSC).; The solubility determined from 0% isosolid line was lower than the measured solubility. The accuracy of solubility determined by 0% isosolid line depends on measurement of 0% solid fat content. |
