Free and Esterified Sterol Distribution in Four Romanian Vegetable Oil

Abstract

The unsaponifiable lipid fraction of plant-based foods is a potential source of bioactive components such as phytosterols, triterpenoids, carotenoids, tocopherols and various hydrocarbons. The free and esterified sterol concentrations in four Romanian edible oils (corn germ, wheat germ, sweet almond and grape seed oil) were determined, including individual values for β-sitosterol, campesterol, stigmasterol, Δ5-avenasterol, sitostanol, campestanol, and cholesterol. Free and esterified sterols were separated by solid-phase extraction (SPE), saponified, and analyzed as trimethylsilyl ether derivatives using gas-chromatography (GC) with flame ionization detector (FID). Differences in total sterol content and the proportion of esterified (ES) and free sterols (FS) were evident for studied oil samples. In general, β-sitosterol was the most prevalent phytosterol, ranging in concentration from 158.3 mg/100 g in grape seed oil to 478.5 mg/100 g in corn germ oil. Only in these two vegetable oil, we identified trace amount of cholesterol (<3 mg/100g). The total sterol concentrations ranged from 199.9 mg/100g (sweet almond oil) to 745.2 mg/100 g (corn germ oil). In corn germ and wheat germ oil, the dominant form of sterols was the esterified one (60.7% ES and 55.6% ES, respectively, of total sterols). This study consolidates the view that vegetable oils are good natural sources of phytosterols. The analyses of these components provide rich information about the identity and quality of vegetable oils. The corn germ and wheat germ oils proved to be the richest sources in phytosterols, being recommended as functional oils.