Oxygen (O2) and reactive oxygen species (ROS) are either directly or indirectly responsible for most of the degradation reactions that take place in food products. Direct oxidation reactions cause the deterioration of food organoleptic and nutritional properties (e.g. degradation of oils, fats, pigments and vitamins), while an example of the indirect action of O2 on food quality is food spoilage by aerobic microorganisms.