Effects of ionizing radiations on fats. II. Accumulation of peroxides and other chemical changes

The accumulation of peroxides, carbonyl com‐pounds and reducing substances during irradia‐tion and post‐irradiation storage of pure fatty acid methyl esters has been studied. Irradiation and storage of irradiated methyl myristate under vacuum results in formation of small quantities of these compounds. Irradiation under oxygen gives peroxides and carbonyl com‐pounds in yields indicating that every ionization results in the formation of one molecule of each group, and antioxidants have no effect on the formation of these compounds during irradiation. Irradiation of methyl linoleate under vacuum results in destruction of pre‐formed hydroperox‐ides. During irradiation in oxygen, approximately one‐eighth of the peroxides formed arises from the direct reaction of irradiation‐induced free radi‐cals with oxygen, while the rest is formed through a chain mechanism with an average chain length of 7. Peroxides continue to accumulate in irradiated methyl linoleate stored under oxygen at a rate increasing with initial irradiation dose. Antioxidants have some effect in retarding the formation of peroxides during irradiation of methyl linoleate and during post‐irradiation stor‐age, but the effect is small compared to their antioxygenic activity toward simple autoxidation. The effect varies with the nature of the antioxi‐dant and with irradiation dose. Propyl gallate is much less effective than butylated hydroxy‐anisole and appears to be easily destroyed during irradiation.