Chapter 2 Supercritical fluid extraction and its application in the food industry DAVID STEYTLER, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ 2.1 INTRODUCTION Solvent extraction is one of the oldest methods of separation known and certainly dates back to prehistory. The science of solvent extraction has evolved accordingly over a long period of time and much progress has been made in the understanding of solvation and the properties of liquid mixtures used in extraction processes. The associated literature on phase behaviour is certainly extensive and, although representation of highly non-ideal mixtures is still problematic, many theoretical models have been successfully developed (Fredenslund, 1975; Hildebrand and Scott, 1950: Prausnitz et aL., 1986). Extensive databanks of pure component properties have grown to support such models in order to predict solvent performance in process applications. Today, even with the introduction of new separation technologies, solvent extraction remains one of the most widespread techniques operating on an industrial scale. Hannay and Hogarth's(1879)early observations of the dissolution of solutes in supercritical fluid (SCF) media introduced the possibility of a new solvent medium. However, it is only in recent years(since 1960) that commercial process applications of supercritical fluid extraction have been extensively examined In the last decade many advances have been made in researching SCF extraction both in terms of fundamental aspects and commercial applications. In particular the high degree of selectivity and control over solubilities afforded by pressure(and temperature) ariation has led to the introduction of many novel SCF extraction and fractionation processes. Of all possible gases, the benign properties(non-toxic, non-flammable)and accessible critical temperature of CO2 have ensured its predominance as a safe SCF solvent for the food industry The essential features of a modern solvent extraction process(using a liquid or SCF solvent medium) are illustrated schematically in Fig. 2. 1. The material to be extractedChapter 2 Supercritical fluid extraction and its application in the food industry DAVID STEYTLER, School of Chemical Sciences, University of East Anglia, Norwich NR4 7TJ 2.1 INTRODUCTION Solvent extraction is one of the oldest methods of separation known and certainly dates back to prehistory. The science of solvent extraction has evolved accordingly over a long period of time and much progress has been made in the understanding of solvation and the properties of liquid mixtures used in extraction processes. The associated literature on phase behaviour is certainly extensive and, although representation of highly non-ideal mixtures is still problematic, many theoretical models have been successfully developed (Fredenslund, 1975; Hildebrand and Scott, 1950; Prausnitz et al., 1986). Extensive databanks of pure component properties have grown to support such models in order to predict solvent performance in process applications. Today, even with the introduction of new separation technologies, solvent extraction remains one of the most widespread techniques operating on an industrial scale. Hannay and Hogarth’s (1879) early observations of the dissolution of solutes in supercritical fluid (SCF) media introduced the possibility of a new solvent medium. However, it is only in recent years (since 1960) that commercial process applications of supercritical fluid extraction have been extensively examined. In the last decade many advances have been made in researching SCF extraction both in terms of fundamental aspects and commercial applications. In particular the high degree of selectivity and control over solubilities afforded by pressure (and temperature) variation has led to the introduction of many novel SCF extraction and fractionation processes. Of all possible gases, the benign properties (non-toxic, non-flammable) and accessible critical temperature of C02 have ensured its predominance as a safe SCF solvent for the food industry. The essential features of a modern solvent extraction process (using a liquid or SCF solvent medium) are illustrated schematically in Fig. 2.1. The material to be extracted is