BODIPY 665/676 has been previously used as a marker to localize lipid oxidation in food emulsions. Oxidation of BODIPY 665/676 can be detected by a shift of fluorescence emission from the red to the green spectral region upon reaction with peroxyl radicals. This reaction causes the cleavage of the phenylbutadiene moiety and the formation of an acid group, which can occur at several positions (Figure ). It has been reported that peroxyl radicals react more rapidly with BODIPY 665/676 (R.9, Table ) than with unsaturated fatty acids (R.3, Table ). However, whether these reactions interact or compete with lipid oxidation is unclear.