ABSTRACT
SuperCritical (SC) Fluids (SCFs) can replace conventional solvents as separating agents to extract and purify phenolics and other natural antioxidants in vegetable matrices and other food materials. A SCF is a substance that is at state conditions above its corresponding critical temperature (Tc) and critical pressure (Pc). SCFs exhibit pronounced changes not only in density with state conditions but also in other relevant properties related to solvation power and mass-transfer rate such as the dielectric constant, viscosity, and self-diffusivity. Under SC conditions, molecules form clusters of high local density (the same as in the liquid state) that do not interact with each other to a great extent (the same as molecules in the gas state), which are respectively responsible for the solvation power and excellent transport properties
5.1 Introduction .................................................................................................. 125 5.2 Literature Survey .......................................................................................... 127 5.3 Phase Equilibrium ........................................................................................ 129 5.4 Applications .................................................................................................. 139
5.4.1 Extraction of Phenolics from Rosemary ........................................... 139 5.4.2 Extraction of Phenolics from Grape Peels, Seeds, Stalks, and
Winery By-Products ......................................................................... 143 5.4.3 Extraction of Phenolics from Tea ..................................................... 149 5.4.4 Classication of Applications ........................................................... 153
5.5 Separation Processes Using Supercritical CO2 ............................................. 154 5.5.1 Batch Extraction from Solid Substrates ............................................ 154 5.5.2 Countercurrent Fractionation from Liquid Substrates ...................... 167 5.5.3 Chromatographic Purication .......................................................... 170 5.5.4 Production of Powders ...................................................................... 171
5.6 Concluding Remarks .................................................................................... 174 Notations ................................................................................................................ 175 Greek Letters .......................................................................................................... 176 Acronyms ............................................................................................................... 176 Acknowledgments .................................................................................................. 177 References .............................................................................................................. 177
(low viscosity, high self-diffusivity) of SCFs. The near-liquid density allows dissolution of target solutes from complex matrices, and the near-gas transport properties allow fast extractions and purications. Moreover, in the absence of separate phases, there is no surface tension, which facilitates interfacial mass-transfer phenomena and inltration of porous solid matrices (Akgerman et al., 1991). Undeniably, the physical properties of SCFs can be tuned to specic separation needs by changing the state conditions, especially near the critical point where an SCF is highly compressible. The recommended extraction conditions are a near-critical temperature [reduced temperature, Tr (= T/Tc) ≈ 1] and a supercritical pressure [reduced pressure, Pr (= P/Pc) ≥ 4] (Brunner and Peter, 1981).
