CHAPTER 3: Supercritical Carbon Dioxide Extraction of Lipophilic Molecules

This chapter will try to illustrate supercritical extraction as a relevant technology for the extraction of higher value products including waxes, essential oils, nutraceuticals and bioactive metabolites. With increased legislation, concerns about the environment and competition within the globalised market, it has become paramount to look for and implement innovative, clean and sustainable ways to obtain natural extracts. Supercritical CO₂ (scCO₂) has favourable health, safety and environmental characteristics, being non-flammable and demonstrating very low toxicity. Perhaps the most important is the fact that it leaves no solvent residues (the solvent can be removed through a simple depressurisation step), making it especially ideal for food, pharmaceutical, cosmetic and personal care products, which require as little solvent as possible. Herein, factors that affect the supercritical process will be discussed and optimisation strategies to give maximal yields of target metabolites will be analysed. The use of supercritical fluids could be a key component of a holistic biorefinery, which may lead to the cost competitive extraction of waxes, bioactive compounds and other lipids, as well as improve the downstream processing of biomass. One of the biggest challenges for biorefineries is the separation of the complex mixtures generated. Supercritical fractionation at the point of extraction offers significant advantages and reduces the need for resource intensive separation processes. Finally, the latest examples of industrial scCO₂ extraction processes will also be highlighted.