5 - Isomeric and Cyclic Fatty Acids as a Result of Frying

Abstract

Deep fat frying is one of the most common procedures for the preparation of food. In this process, fat is exposed to high temperatures in the presence of air and food containing water. Consequently, many chemical reactions take place during this process. Hydrolysis results in the formation of fatty acids, monoglycerides, and diglycerides, while the presence of air and high temperatures gives rise to the formation of thermal and oxidation alteration products. Oxidation products may include oxidized monomeric, dimeric, and oligomeric triglycerides, as well as volatiles components such as aldehydes, ketones, hydrocarbons, etc. Thermal alteration products include Cyclic Fatty Acid Monomers (CFAM), fatty acid geometrical isomers, non-polar dimeric, and oligomeric triglycerides. Thus, frying is a complex situation where many reactions take place. This chapter reviews the structural analysis and identifications of geometrical fatty acids isomers, including those having a conjugated system, and the CFAM formed from both essential fatty acids and linolenic acids. It also describes the methods of analysis, quantification, and levels in food products and, emphasizing on the CFAM, considers the great number of studies carried out on these molecules.