Lipid extraction procedure for some food products containing surfactants

Total lipids were extracted from food products by heating the sample under total reflux for 15 hr with a mixture of chloroform--methanol (70 + 30) in the ratio 6.67 mL solvent/g sample. The solution was filtered and evaporated, and the lipids wer dissolved in petroleum ether, filtered, and evaporated to yield the crude lipids and surfactants. The purified lipids are suitable for butterfat determination directly, or are readily separated from the surfactants by alumina chromatography. The method is particularly suited to the milk products studied, which produced troublesome emulsions if aqueous treatments were used. The method also allows ready extraction of total fats from drained feta cheeses, whereas Soxhlet extraction with petroleum ether sometimes fails. The effects of reflux time and varying ratios of chloroform to methanol were studied.