7 - Formation, Analysis, and Health Effects of Oxidized Sterols in Frying Fat

Abstract

Sterols, minor compounds present in dietary fat, comprise a major portion of the unsaponifiable matter of most vegetable oils. They are mainly present as free sterols and esters of fatty acids, in addition to sterol glucosides and acetylated. Vegetable oil sterols are collectively known as plant sterols or phytosterols. Sterols vary with the origin of the fat and are affected by food processing. Cholesterol is the main animal sterol, while β-sitosterol, campesterol, stigmasterol, brassicasterol, avenasterol, and stigmastenol are major plant sterols present in vegetable oils at much higher levels than cholesterol is in animal fats. Sterols share a similar chemical structure that undergoes oxidation in the presence of oxygen. This chapter provides an overview of the formation, analysis, and health effects of oxidized sterols in frying fat. It reviews the techniques used for the analysis of sterol oxidation products in food and biological matrices and discusses the health implications of phytosterol-oxidized products in addition to those reported for cholesterol-oxidized products. Oxidation products of cholesterol are of considerable interest because of their possible effects on human health. As more vegetable oil is used for cooking, it is necessary to consider the occurrence and effect of plant sterol oxides. This became particularly apparent when it was observed that vegetarians absorbed more phytosterols than did those on non-vegetarian diets. This implies that the effects could be greater than previously perceived. Work with oxidation products of plant sterols has expanded due to the availability of analytical methods.