Effect of Chemical Structure of Solid Lipid Matrix on Its Melting Behavior and Volumetric Expansion in Pressurized Carbon Dioxide

Abstract Supercritical carbon dioxide (SC‐CO2) technology offers new opportunities for green processing of lipids; however, there is little information of the melting behavior and volumetric expansion of solid lipids in pressurized CO2. In this study, melting behavior and volumetric expansion of two different solid lipid classes and the effect of the structural differences within the same lipid class on the melting behavior in pressurized CO2 were investigated. The melting point of the solid lipids decreased linearly with increasing pressures up to a certain level; then, it stayed constant. The highest melting point depression was observed for soybean oil monoacylglycerol (SO‐MAG) at 51.5 °C/110 bar, whereas the lowest was for fully hydrogenated soybean oil (FHSO) containing 30% SO‐MAG at 55.0 °C/79 bar. Melting point depression depended on lipid class. SO‐MAG exhibited a higher melting point depression than FHSO (triacylglycerol form), and its blends with SO‐MAG. There was no difference in melting point depression between glyceryl 1,2‐distearate and glyceryl 1,3‐distearate up to 200 bar (P > 0.05). A positive correlation between the melting point depression and volumetric expansion of solid lipids was observed. The highest volumetric expansion was for SO‐MAG in the linear region of the melting point depression curve, achieving 14.4% expansion compared to 9.3% for FHSO (P < 0.05). The highest dT/dP value (0.17 °C bar−1) was obtained for SO‐MAG, whereas the FHSO (0.09 °C bar−1) had the lowest one. Findings of this study will help optimize solid lipid‐involving SC‐CO2 processes for better protection of heat‐sensitive compounds while improving energy efficiency.