Effect of triolein addition on the solubility of capsanthin in supercritical carbon dioxide

This manuscript presents new phase equilibrium data for capsanthin in pure and triolein-entrained Supercritical (SC) carbon dioxide (CO2). The aim of the work was to determine the cosolvent effect of triolein on capsanthin by comparing solubility results in a ternary (CO2 + triolein + capsanthin) system and binary (CO2 + capsanthin) system at (313 or 333) K and (19 to 34) MPa. For this, authors isolated capsanthin from red pepper (Capsicum annuum L.) and tested it using a dynamic-analytical method in an apparatus with recirculation and online analysis of the CO2-rich phase. Within the experimental region, the solubility of capsanthin in pure SC–CO2 increased with system temperature at isobaric conditions and also increased with pressure at isothermal conditions. Solubilities ranged from a minimal of 0.65 μmol/mol at 313 K and 19 MPa to a maximal of 1.97 μmol/mol at 333 K and 32 MPa. The concentration of triolein in the ternary system was equivalent to that its solubility in pure SC–CO2 depending on system temperature and pressure conditions. Crossover pressure was determined experimentally at 29.6 MPa, below which solubility of triolein decreased with temperature (effect of density). Above the crossover pressure, solubility of triolein increased with temperature (vapor pressure effect). Values of solubility within this range were 0.16 mmol/mol at 19 MPa and 313 K to 0.41 mmol/mol at 33 MPa and 333 K. Independent of system temperature and pressure, capsanthin solubility in triolein-entrained SC–CO2 increased by a factor of about 3 (triolein-induced enhancement factor) as compared to its solubility in pure CO2, under similar conditions of pressure and temperature. The maximal solubility of capsanthin in SC–CO2 experimentally observed in this study was 5.27 μmol/mol at 333 K and 33 MPa in the presence of 4.10 mmol/mol triolein.

► We isolated capsanthin from red pepper (Capsicum annuum L.).
► We measured its solubility in pure CO2 and with triolein as cosolvent.
► We model the solubility of capsanthin in pure CO2 and with triolein.
► Solubility of triolein in mixtures CO2 + capsanthin was similar to pure CO2.
► Triolein has cosolvent effect over solubility of capsanthin in CO2.