Pressurized liquid extraction of lipids for the determination of oxysterols in egg-containing food

Pressurized liquid extraction (PLE, ASE) was compared with the Folch proced ure (a solid-liquid extraction with chloroform/methanol 2:1, v/v) for the l ipid extraction of egg-containing food; the accuracy of PLE for the quantit ative determination of oxysterols in whole egg powder was evaluated. Sample s of spray-dried whole egg, an Italian vanilla cake (Pandoro) and egg noodl es were used. Two different extraction solvents (chloroform/methanol 2:1, v /v, and hexane/isopropanol 3:2, v/v) were tested at different extraction te mperatures and pressures (60 degreesC at 15 MPa, 100 degreesC at 15 MPa, 12 0 degreesC at 20 MPa). No significant differences in the lipid recovery of the egg powder sample using PLE were found. However, PLE of the vanilla cak e and egg noodles with the chloroform/methanol mixture was not selective en ough and led to the extraction of a non-lipid fraction, including nitrogen- containing compounds. In the same samples, the pressurized hexane/isopropan ol mixture gave a better recovery result, comparable to that obtained using the Folch method. Cholesterol oxidation products of the Folch extract and the pressurized liquid extract of spray dried egg powder (obtained with hex ane/isopropanol 3:2, v/v, at 60 degreesC and 15 MPa) were determined by gas chromatography. PLE performed under these conditions is suitable to replac e the Folch extraction, because the differences between the two methods tes ted were not statistically significant. Moreover, PLE shows important advan tages, since the analysis time was shortened by a factor of 10, the solvent costs were reduced by 80% and the use of chlorinated solvents was avoided. (C) 2001 Elsevier Science B.V. All rights reserved.