Gas Expanded Liquids (GXL) are mixtures of liquid solvents (organic,
water) and gases or supercritical fluids with diverse physicochemical properties
halfway between pure liquids and supercritical fluids. The possibility of changing their
properties by introducing small changes in pressure, temperature, and/or solvent/gas
ratio, makes these solvents a very interesting and appropriate option for developing
green extraction protocols for food analysis. In general, GXLs have similar densities as
the solvent used in their composition, while having improved mass transfer through
reduced viscosity, increased solute diffusivity, and decreased interfacial tension. Some
other advantages are related to the wide range of polarities that can be obtained,
depending on the liquid selected. Moreover, the substitution of a liquid fraction for a
gas reduces the final use of organic solvent, thus improving the green character of
GXLs. In the present chapter, the physicochemical properties of GXL are addressed
along together with the description of applications in the food science and technology
area.
Keywords: Biorefinery, By-products, Food analysis, Gas-expanded liquids, Green solvent, Natural compounds.