Detection and quantification of phytosterols in yogurt using gas chromatography

Sterols form the largest proportion of the unsaponifiable fraction of lipids. Plant fats and oils contain phytosterol as naturally occurring constituents. The most common types of phytosterols in plants are cytosterol, compressor and stigmometol. Different types of yogurt and especially high-fat types are foods that are likely to contain added phytosterol. In this study, the presence of cholesterol and four phytosterols in 62 different yogurts in Tabriz city was investigated in order to assess the addition of vegetable oils. For this purpose, after saponification and liquid-liquid extraction of the samples, non-absorbent materials were purified by thin layer chromatography. Then, without the derivative step, the compounds were detected by gas chromatography with a flame ionization detector. In the recent study, the saponification process was optimized and validated. According to the results, the method was estimated as easy, fast and repeatable, and had a high efficiency in detecting sterols in our samples. Cholesterol was found as the highest sterolic compound in all samples (65-99%). Among the phytosterols, campesterol was predominated (4.7%) followed by brassicasterol (2.08%). According to the guidelines of Institute of Standards and Industrial Research of Iran, 46 (74.2%) yogurt samples were found unacceptable.