QUANTIFICATION OF CHOLESTEROL OXIDATION-PRODUCTS IN MILK POWDERS USING [H-2(7)]CHOLESTEROL TO MONITOR CHOLESTEROL AUTOXIDATION ARTIFACTS

Cholesterol oxidation products (COPs) may produce adverse biological effects, and there is increasing concern regarding the potential health implications of these products in the diet. We have developed a GC/MS method allowing the quantification of COPs in commercially available milk powders and infant formulas. Since oxidation artifacts from cholesterol are essentially impossible to avoid, we have used a deuteriated cholesterol probe to precisely monitor the formation of cholesterol oxidative artifacts during all stages of sample analysis. This strategy allowed the determination of the artifact-free cholesterol oxide content of the samples. We found that freshly opened full cream powders which had been packed under inert gas contained only traces of COPs (<250 ng/g total). Infant formulas were also found to contain very low levels of COPs. Our values were considerably lower than those previously reported, especially for 7-ketocholesterol. This difference is at least in part explained by the correction of the oxidation artifacts applied to our samples. We conclude that the exposure to COPs from commercial milk powders and infant formulas, and consequently their potential health hazard, may have been previously overestimated.