The vdW EoS hundred years later, yet younger than before. Application to the phase equilibria modeling of food-type systems for a green technology

The relevant applications that supercritical fluid extraction (SFE) has attained in the food industry in the last decades increased the interest in the development of thermodynamic models to represent the phase equilibria of systems comprising food-related substances and supercritical carbon dioxide (SCCO2). The targets are twofold: (i) calculation of solid solubilities in SCCO2 pure or with polar co-solvents (mainly ethanol in food applications), what directly affects the selectivity of one of the most applied processes, e.g. the semi-batch SFE of plant material, and (ii) calculation of vapor–liquid equilibrium compositions of liquid raw materials processed in countercurrent packed columns, what is straightforwardly related with the number of theoretical stages necessary to achieve the desired separation.Cubic equations of state derived from the equation proposed by van der Waals (vdW-type EoSs, e.g. Peng–Robinson and Soave–Redlich–Kwong EoS) are the most common thermodynamic models applied to achieve these objectives.In this work, the application of vdW-type EoSs to food-type substance + SCCO2 is reviewed. More than 100 systems, comprising lipids, antioxidants, pigments, alkaloids, vitamins, etc. were investigated from 2003 up today. Even though phase equilibria modeling of SCCO2 + food-related systems involves serious difficulties, the extensive and, in many cases, successful application of vdW-type EoSs demonstrates that though developed 100 years ago the van der Waals equation is lively and younger than before.

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