The separation factor for solvent extraction is the chemical equilibrium of the component between solid and solvent phases and the driving force of the solvent extractions the difference or gradient of chemical potential of a given species between an organic phase and an aqueous phase.
The difference in solubility relate mainly to issues of charge or polarity and the nature of the association between food and other components with the material to be extracted.
Once a solid is in contact with a solvent, the concentration difference drives a net flow of solutes from the solid phases to the solvent in an attempt to reach equilibrium. The bigger the concentration difference, will give the larger the driving force and the more efficient the extraction.
Solvent extraction used in numerous chemical industries to produce pure chemical compounds ranging from pharmaceuticals, food, and biomedical to heavy organics and metals, in analytical chemistry and in environmental waste purification.
Oleoresins are one example of the products of the extraction of spices and herbs using an organic solvent, followed by the removal of the solvent.
In United States solvent extraction with petroleum ether has been used primarily for the production of soybean oil.
Chemical solvent extraction in food