Directly resistively heated-column gas chromatography for the evaluation of cow milk fat purity

Cow milk fat purity is currently evaluated by triacylglycerol (TAG) analysis. The method is based on the gas chromatographic analysis of TAG according to their total number of carbon atoms, followed by the application of formulae deriving from multiple linear regressions. The original procedure was set up by using a packed column, but different successive works showed its suitability also with the adoption of more modern adjustments. Recently, the use of high-speed gas chromatography has been spreading. In this work, the suitability of the directly resistively heated-column gas chromatography [Ultrafast module (UFM)-GC] for the evaluation of milk fat purity by the Official EU method was tested. Pure milk fat, together with mixtures of milk fat containing two levels of four foreign fats (coconut fat, sunflower oil, lard and beef tallow), were analyzed by both the conventional capillary GC method and UFM-GC. Sheep, goat and buffalo milk fats were also analyzed. The reference material CRM-519 was used for calibration. Repeatability and reproducibility values were always below the limits reported in the Official method, demonstrating the suitability of UFM-GC for the evaluation of milk fat purity. The investigation on sheep, goat and buffalo milk fat confirmed that the S ranges, calculated for cow milk fat, are not applicable to the evaluation of genuineness of non-bovine milk fats.