Phase equilibria and physical properties of CO2-saturated cocoa butter mixtures at elevated pressures

The melting point and phase behaviour of cocoa butter under CO2 pressure were observed in a high-pressure view cell. The melting point decreases from 35 to 23 °C at CO2 pressures higher than 5 MPa. A static analytical procedure was used to measure the solubility of CO2 in cocoa butter at 40, 80 and 100 °C and pressures of 2-35 MPa in an autoclave set-up. The density and viscosity of the CO2-saturated cocoa butter was measured simultaneously in this set-up. The experimental procedure was first validated by comparing the data measured for the system CO2/hexadecane with literature data. The highest solubility of CO2 in cocoa butter of 36 wt.% occurs at 40 °C and 35 MPa. The measured solubilities differed from those previously reported in literature. This can be attributed to differences in the cocoa butter used for measurements. The density of CO2-saturated cocoa butter increases with pressure, whereas the viscosity decreases. The Grunberg equation was used to correlate the viscosity of CO2-saturated cocoa butter. The measured data were used to estimate the theoretical gas assisted mechanical expression (GAME) yields. In GAME CO2-saturated cocoa nibs are mechanically expressed. The calculated GAME yields deviate from the experimental ones due to the oversimplification of the mechanism involved in GAME.