Melting Temperature Depression of Solid Lipid under High Pressure Gases

The effects of high pressure gases on solid lipids were investigated by high-pressure differential scanning calorimeter (DSC). In particular, the influence of a high-pressure gas on solid-liquid and solid-solid transitions were investigated for pure tristearin and a mixture of lipids (tristearin-phosphatidylcoline-dioctilsolfosuccinate). Both of these substances are commonly used for the production of solid-lipid-nano-particles by highpressure processes. The investigations were carried out in the presence of CO2, CHClF2 and CH2FCF3 at different operating pressures up to 7.0 MPa. The melting and solidification temperatures were measured for six different systems. As regards the experiments under CO2, the results indicate a melting point depression as function of the gas pressure, with a maximum 25 K at 6 MPa. The same performances of CO2 were reached using CHClF2 at maximum pressure of 0.45 MPa. CH2FCF3 exhibits lower melting temperature depression. These results highlight the possibility of processing liquid lipids and thermosensitive compounds at mild temperature condition below 313 K and at moderate gas pressure.