VALIDATION OF DIGLYCERIDE CONTENTS IN CHEESES USING CO-ORDINATED CHROMATOGRAPHIC TECHNIQUES

This paper describes a method suitable for the analysis of diglycerides (DG) in cheese. The method, also suitable for other foods, is essentially based upon the solid-phase extraction (SPE) of DG followed by capillary gas chromatographic analysis with a polar stationary phase (TAP). SPE is applied to avoid the column overloading caused by triglycerides; however, SPE is able to catalyse isomerization from the 1,2-form to the 1,3-form. This introduces an error into the results, as the two forms have different origins and are produced at different stages of ripening. A comparison between the use of silica and diol phases was made and it was seen that no isomerization occurred when the diol phase was used. Repeatability and recovery trials were carried out and the coefficient of variation (relative standard error) of the former trial was approximately 10%. Finally, it is demonstrated that it is possible to re-use the SPE cartridge at least four times.