Sodium azide and metal chelator effects on 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging compounds from methylene blue photosensitized lard

Thermal oxidation of edible oils can generate 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging compounds from oxidized lipids (RSOLs). However, effects of photosensitization on the formation of RSOLs have not been reported yet. Methylene blue (MB) photosensitization and involvement of singlet oxygen and transition metals on the RSOL formations were determined in stripped lard oils. RSOLs were formed in lard containing MB and visible light irradiation only. Addition of sodium azide decreased RSOLs with concentration dependent manner, which implies singlet oxygen was involved on the RSOL formation. Ethylenediammetetraacetic acid (EDTA), a well known metal chelator, accelerated the formation of RSOLs through protecting the decomposition of MB photosensitizer. Results from p-anisidine values showed that RSOLs from photosensitization may not be formed from the same pathways compared to thermal oxidation.