Measurement and modeling of the high-pressure phase equilibria of CO2-Oleoresin Capsicum

Oleoresin Capsicum is one of the most important sources of natural colorants with a lot of applications in food industry due to its carotenoids concentration. With high content of lipid matter and a noticeable amount of capsaicinoids, Oleoresin Capsicum can also be used in pharmaceutical industry or for self-defense sprays. In this work, the phase equilibrium of Oleoresin Capsicum in supercritical carbon dioxide was measured by a recirculation method at pressures between 90 and 315 bar and temperatures of 314.7, 326.4 and 337.8 K. The experimental data were correlated using Soave–Redlich–Kwong (SRK) equation of state with Mathias–Klotz–Prausnitz as mixing rule, and binary interaction parameters were obtained. Moreover, the prediction of the pseudo-binary system CO2/Oleoresin Capsicum was carried out with the Group Contribution Equation of State (GC-EoS), using the set of binary group parameters established in a previous work. For all isotherms studied, the solubility of Oleoresin Capsicum in the gaseous phase and that of CO2 in the liquid phase increases with an increase in pressure. Comparison between experimental data and those correlated by SRK or predicted by GC-EoS, shows that SRK correlation produced better fittings of the experimental data. Nevertheless, the importance of data predicted by GC-EoS is based on the possibility to obtain an approximation to the thermodynamic behaviour of the real systems without the necessity of experimental data.

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► P-x,y diagrams of the system CO2-Oleoresin Capsicum were experimentally obtained.
► Oleoresin Capsicum had to be defined as a pseudocompound to model experimental data.
► Correlations obtained with Soave–Redlich–Kwong fits good experimental data.
► GC-EoS predictions for the system overestimate the solubility.
► Predictions can be obtained inclusively when experimental data are not available.