Analysis, Formation and Inhibition of Cholesterol Oxidation Products in Foods: An Overview (Part I)

Abstract

Cholesterol oxidation products (COPs) formed in cholesterol-containing foods during heating or illumination have been found to impart a potential hazard to health. Numerous studies have indicated that COPs may have several adverse biological effects, such as mutagenicity, carcinogenicity, angiotoxicity, cytotoxicity, atherogenicity, atherosclerosis, cell membrane damage and inhibition of cholesterol biosynthesis. Therefore, the safety of COPs has become a major concern for the public. This paper is an overview of analysis, formation and inhibition of COPs in foods. COPs are routinely extracted by organic solvents, followed by saponification and solid phase extraction for enrichment of COPs, and separation and identification by thin-layer chromatography (TLC), high-performance liquid chromatography (HPLC) or gas chromatography-mass spectrometry (GC-MS). The identification and quantification of COPs using the GC-MS technique was found to be rapid and sensitive, however, the formation of artifacts is a major drawback. The HPLC method failed to resolve several geometrical isomers, and double bond-free COPs such as isomeric 5,6-epoxides and triol could not be detected with UV. The oxidation of cholesterol can be accelerated by heating, pH, storage conditions, the presence of food components and other factors. Several COPs are commonly present in food systems, including 7α-OH, 7β-OH, 5,6α-EP, 5,6β-EP, 7-keto, 20α-OH, 25-OH and triol. Of these COPs, 5,6α-EP, 5,6β-EP, 7-keto, 20α-OH and 25-OH are primary oxidation products, while 7α-OH, 7β-OH and triol are secondary products. Some antioxidants have been found to reduce the formation of COPs in an appropriate concentration. Also, adequate packaging is necessary to provide a physical barrier for air and light, and thus minimize cholesterol oxidation. Further research is necessary to study how to inhibit COPs formation in foods.