Lipid modification processes induced by thiyl radicals

•The preparation procedure of LiH model systems affects the thiyl radical reactivity.•Above 400 Gy lipid peroxidation was drastically reduced.•Geometrical isomerization of LiH reached maximum at 2 kGy in equilibrium with air.•In food irradiation doses up to 10 kGy may result in permanent lipid modifications.

Polyunsaturated fatty acid (PUFA) oxidation by thiyl radicals (RS•) is believed to be responsible for some of the biological radiation damage. At the same time, RS• can cause isomerization of PUFA double bonds with the formation of trans isomers. The aim of this study was to better understand the competition between lipid peroxidation and geometrical isomerization processes in biomimetic model system of linoleic acid in the presence of 2-mercaptoethanol using irradiation as a method for free radicals generation. In air-equilibrated conditions the propagation of lipid peroxidation was dominant up to the dose of 400 Gy, after which at higher doses up to 10 kGy the termination occurred with the predominance of geometrical isomerization. This study revealed that undesirable and permanent lipid modifications are possible at higher irradiation doses which should be considered in the planning of irradiation treatment of foods and feeds with high content of lipids and sulfur compounds.