TRANSESTERIFICATION AND ONLINE LC-GC FOR DETERMINING THE SUM OF FREE AND ESTERIFIED STEROLS IN EDIBLE OILS AND FATS

A method is proposed to substitute the classical saponification procedure for the determination of the sterols and other minor components in edible oils and fats. Saponification is replaced by transesterification, which liberates sterols and alcohols from esters under mild conditions, but does not form soap hindering the extraction of the neutrals. Triglycerides are turned into fatty acid methyl esters, which are removed by automated LC-GC. LC also pre-separates the minor components into classes, e.g., of linear alcohols, triterpenes, methyl sterols, DELTA5 sterols, and DELTA7 sterols. Multiple LC-GC transfer allows obtaining several gas chromatograms from the same injection into LC. Sample preparation takes some 5 min; 10-25 samples can be analyzed by an LC-GC instrument, depending on the number of LC fractions transferred to GC per sample.