Analysis of foods containing large amounts of lecithin (e.g. eggs, egg liquid, milk powder, soybeans, mayonnaise) without pretreatment. Determine the dry weight of each sample.
Extract foods containing small amounts of lecithin (e.g. noodles, ice cream, cakes, pastries) with ether in a Soxhlet extractor. All lecithin was extracted into the ether layer. Analyze this.
The lipid was dissolved in ether and the lecithin was quantitatively precipitated with acetone (after addition of a saturated MgCl2 solution)11). The precipitate was dissolved in ether and the solution analyzed.
For the preparation of food for analysis see also 12).
Extract animal tissues, blood, plasma, and serum with ethanol-ether, petroleum ether-chloroform, and hot chloroform-methanol (see 13, 14)). The solvent was evaporated and the residue was dissolved in ether.
Sample Collection and Processing
Foodstuffs (e.g. eggs, egg liquid, milk powder, soybeans, mayonnaise), pharmaceuticals and cosmetics, as well as pure lecithin, which contain large amounts of lecithin can usually be analyzed without pre-extraction. Dissolving the sample in ether or adding a finely powdered or well-suspended weighed amount (equivalent to 5-50 mg lecithin) to the assay system is usually sufficient12.
Free phospholipids, except sphingomyelin, are soluble in ether but insoluble in acetone or methyl acetate.
what is lecithin
Bound phospholipids can only be extracted after initial treatment with ethanol or ethanol/chloroform or ethanol/benzene 13-16 . The ease with which lecithin is completely extracted from tissues depends on the degree of protein binding. By treatment with an alcoholic solvent, the protein is denatured and lecithin is released.
Animal tissues, blood, plasma and serum are delipidated (phospholipid precipitation) with 3 volumes of acetone at low temperature. Absorb the filter cake with a mixture of ethanol/diethyl ether (3:1) or petroleum ether/chloroform (2:1) at room temperature. After homogenization, centrifugation, the precipitate was extracted in a similar manner. The extracts were combined, the solvent was evaporated under nitrogen at 40 °C, and the residue was dissolved in diethyl ether17,18.
Oils and fats or other fat-rich samples are dissolved in ether or made into a fine suspension and the lecithin is precipitated with 4 to 5 volumes of ice-cold acetone (a spatula tip with calcium or magnesium chloride dissolved in it). The precipitate was dissolved in ether and analyzed 14,19 . Alternatively, after 3-4 extractions directly with acetone and salt (this results in a significant fat separation), the insoluble residue is dissolved in ether and aliquoted for analysis.
a finely powdered or well-suspended weighed