DETERMINATION OF CHOLESTEROL OXIDES IN HEATED LARD BY LIQUID-CHROMATOGRAPHY

The presence of cholesterol oxidation products (COPS) in heated lard by liquid chromatography was studied. Lard was heated at 180 degrees C for 0, 2, 4, 8, 10, 20, 50, 70, 100, 150 and 200 h. The various COPS present in heated lard were analysed by thin-layer chromatography and high-performance liquid chromatography. 6-Ketocholesterol was used as an internal standard to quantify all the compounds. Results implied that in most cases the COPS content increased along with the increase of heating time. The only exception was that both 5,6 alpha-epoxycholesterol (5,6 beta-epoxycholestanol) and 7 beta-hydroxycholesterol contents increased during the first 100 h and then began to decline. Cholestan-3 beta 5 alpha-6 beta-triol could be detected only after 20 h heating, and reached plateau as the heating time increased to 200 h The loss of cholesterol reached 70% after 150 h heating, and the amount of cholesterol lost during heating was not equal to the amount of COPS formed. Surprisingly, the highly toxic 25-hydroxycholesterol was not found.