Supercritical Fluid Adsorption of Natural Extracts: Technical, Practical, and Theoretical Aspects

• Practical, technical, and theoretical SFA aspects of natural extracts are presented. • SFC and SFI of natural extracts is discussed from the point of view of concentration and impregnation. • SFA is an alternative process to produce well-designed natural products. • SFA coupled with other high-pressure processes can integrate the concept of biorefinery. Supercritical fluid adsorption (SFA) is a feasible and novel technique that combines the adsorption process with supercritical fluid technology. Nowadays, two techniques originating from SFA are being investigated, supercritical fluid chromatography (SFC) and supercritical fluid impregnation (SFI). SFC aims to achieve a higher concentration of the target compounds or remove undesirable substances through a chromatographic column. SFI aims to impregnate the target compounds in porous materials to protect them against degradation and to promote their controlled release. This work reviews the main applications of SFA in the natural extracts field. First, the principles, technical and practical aspects of supercritical adsorption processes are addressed. Next, a critical review of the literature from the last 15 years on the SFC and SFI processes of natural extracts is presented, emphasizing SFC in semi- and preparative scales and the use of SFI for the development of food packaging and drug delivery of bioactive compounds. Adsorption isotherms are reported for mono-component and multi-component systems. Moreover, the integration between SFA and other high-pressure processes is described and exemplified for natural extracts. Finally, emerging topics and potential opportunities for future innovations are outlined.