Cold Extraction of Total Lipids from Biological Materials and Food Matrices with Mixtures of Polar and Apolar Solvents

Lipid extraction from its original matrix is a crucial step to determine the lipid content of a food product or to get, before further analysis, a representative lipid extract not biased by selective extraction. Extraction should also avoid the deterioration of the original lipids and ensure the elimination of nonlipid materials. Pretreatment of the samples and precautions required to disintegrate the matrix and improve lipid accessibility to the solvents, deactivate lipolytic and oxidative enzymes, and avoid oxidation during all steps of the procedures are first underlined. Then protocols to extract at ambient temperature total lipids from complex food matrices with mixtures of nonpolar and polar (alcohols) organic solvents are detailed. Three of them, based on the phase diagram of the chloroform/methanol/water ternary mixture, were directly adapted from the methods of Folch et al. (J Biol Chem 226:497–509, 1957) and Bligh and Dyer (Can J Biochem Physiol 37:911–917, 1959). The last one takes the advantage of the hexane/isopropanol mixture (Hara and Radin, Anal Biochem 90:420–426, 1978). The criteria for choosing one or the other method for a given matrix are presented. The parameters to adapt and the crucial steps and/or conditions for extraction are also highlighted.