DETERMINATION OF MIXTURES IN VEGETABLE-OILS AND MILK-FAT BY ANALYSIS OF STEROL FRACTION BY GAS-CHROMATOGRAPHY

A rapid gas-chromatographic (GC) procedure was developed for the analy sis of the total sterol fraction of vegetable oils, milk fat or mixtur es, to detect possible admixtures of sunflower with olive oil and the addition of vegetable oils to milk fat. The method, which employs alka li-catalyzed transesterification with KOH/methanol, was compared with saponification procedures with and without transformation of sterols i nto silyl derivatives prior to analysis. Repeatability of the method w as assessed, and the coefficient of variation was 6.0 and 8.0% for bet a-sitosterol in olive and sunflower oils, respectively. Recovery of be ta-sitosterol ranged from 92.6 to 95.8 for both oils. The GC method as sayed in this work requires little analysis time and eliminates the ne ed for saponification, extraction, and derivatization steps. It offers good repeatability and recovery and is thus well suited to routine us e.