Determination of sterols in dairy products and vegetable fats by HPLC and GC methods

Abstract

Cholesterol concentrations in goat milk, goat milk cheeses, ewe's milk, ewes milk cheeses, dairy bioprod-ucts, and concentrations of cholesterol, stigmasterol and sitosterol in butter, butter with added vegetable fats and margarines were evaluated by RP HPLC method. Parallel analyses by capillary GC were performed. Prior to the final chromatographic analyses the saponification step was used, followed by the extraction of the unsaponificable residue into n-hexane. Parameters of RP HPLC method were compared with parameters of GC determination. The detection limits (LOD) determinated on the bases of blank samples analysis were 5.2 mg/kg for cholesterol, 4.8 mg/kg for stigmasterol and 14.7 mg/kg for sitosterol. Recovery ranged between 80-92%, repeatibility expressed as RSD of 12 parallel samples measurements was 4.2-6.8%. Accuracy tested on the SRM 1845 Whole Egg Powder (NIST) was 95.7%.