ABSTRACT
I. INTRODUCTION Oxidation can alter the flavor and nutritional quality of foods and produce toxic compounds, all of which can make the foods less acceptable or unacceptable to consumers [1]. Oxidation products typically include low molecular weight compounds that are volatile as well as undesirable off-flavor compounds [2,3]. Triplet oxygen lipid oxidation of foods has been extensively studied during the last 70 years as part of the effort to improve the oxidative stability of foods [4,5]. However, triplet oxygen oxidation does not fully explain the initiation step of lipid oxidation [6,7]. Rawls and VanSanten [8] suggested that singlet oxygen is involved in the initiation of triplet oxygen lipid oxidation because singlet oxygen can directly react with double bonds without the formation of free radicals. Singlet oxygen oxidation can be very rapid in foods due to the low activation energy required for the chemical reaction. The reaction rates of singlet oxygen and triplet oxygen with linoleic acid are 1.3 105 M1 s1 and 8.9 101 M1 s1, respectively [8,9]. For many foods containing lipids, special measures are taken to reduce or prevent oxidation, such as removal of oxygen, addition of antioxidants, and use of gas barrier packaging materials.
