These solubility differences primarily relate to issues of charge or polarity and the nature of the association between lipids and the other components within the material to be extracted.
Neutral or non-polar lipids such as hydrocarbons, sterol esters, acylglycerols and carotenoids can be bound through non-covalent interactions such as van der Waals forces and hydrophobic associations between hydrocarbon chains of lipids and hydrophobic protein domains within foods.
Depending on its efficiency the extraction procedure should be repeated to ensure total recovery of lipids. Generally, extractions are performed in triplicate.
Solvent extraction becomes more efficient when sample is heated and extraction is continues. In a Soxhlet apparatus, dried and homogenized sample are weighed in thimbles that are subjected to steady extraction with heated solvent for several hours.
Solvent extraction of lipids