The Oxidation Mechanisms of Saturated Fatty Acids: Formation of Hydroperoxide Isomers and Production of 2-Alkanones and Lactones

Abstract

Saturated fatty acids (SFAs) are generally regarded simply as being resistant to oxidation compared with unsaturated fatty acids. However, it has long been reported that SFAs can undergo oxidation when heated at high temperatures, leading to the formation of unique degradation products such as 2-alkanones and lactones. Research on SFA oxidation was intensively conducted approximately half a century ago, and during this period, a mechanistic hypothesis for the formation of 2-alkanones and lactones appears to have been proposed. Owing to technical limitations at the time, this hypothesis could not be verified, and research on SFA oxidation subsequently stagnated for several decades. In recent years, however, the hypothesis concerning the formation mechanisms of 2-alkanones and lactones during SFA oxidation has been experimentally validated through an approach involving the individual preparation of SFA hydroperoxide positional isomers and their thermal decomposition. Because 2-alkanones and lactones are aroma-active constituents commonly found in dairy products and beef, SFA oxidation has significant implications for food chemistry. In this review, we revisit previous studies on SFA oxidation and the hypothesis proposed at that time, describe the mechanisms that are now being elucidated, and discuss emerging applications and future perspectives in food chemistry.