The presence of chlorophyll pigments in oils has a negative effect on their taste, smell, colour, clearness, thermal stability and shelf life. Those compounds are strong photosensitisers in oxidation processes of unsaturated bonds of lipids, what negatively impacts the oxidative stability of oil during storage.The objective of the research study was to evaluate the photooxidation activity of chlorophyll pigments in rapeseed oil by the UV-A radiation. A refined rapeseed oil and its triacylglycerols (TAG) constituted a research material. As photosensitisers were used chlorophyll a and pheophytin a. The photooxidation process was monitored using the determination of the content of singlet oxygen, volatile compounds and chlorophyll pigments. It was shown that chlorophyll pigments were photosensitisers in photooxidation of rapeseed oil and TAG during their exposure to the UV-A radiation. Chlorophyll a and pheophytin a participate in the generation of singlet oxygen. The photosensitising efficiency of chlorophyll a is higher than that of pheophytin a. Chlorophyll pigments have a diversified effect on the content and profile of volatile substances formed during the photooxidation of oil and TAG. The type of photosensitiser has a significant impact on the total volatile compounds and hexanal content in the TAG. The maximum level of volatile compounds is found at a photosensitiser dose of 0.5 mg/kg. Chlorophyll pigments are degraded as a result of the oxidation with singlet oxygen during photooxidation of the rapeseed oil and TAG. Pheophytin a is more difficult to degrade than chlorophyll a. The accompanying substances play an important protective role against the photooxidation of rapeseed oil. Their removal contributes to a higher singlet oxygen uptake, an increase in the total volatile compounds content, changes in their profile and an increased degradation of chlorophyll pigments. Chlorophyll pigments adversely affect the oxidative stability of rapeseed oil when exposed to the UV-A radiation and they should be removed therefrom.
rapeseed oil, photosensitized oxidation, chlorophyll pigments, singlet oxygen, volatile compounds