Chemiluminescence detection of mono-, bis-, and tris-hydroperoxy triacylglycerols present in vegetable oils

A reliable method was needed to analyze molecular species of oxidized vegetable oils. In order to accomplish this goal, mono-, bis-, and tris-hydroperoxides (Mono-OOH, Bis-OOH, and Tris-OOH, respectively) of triacylglycerols formed during autoxidation and photosensitized oxidation of oils were determined by reversed-phase high-performance liquid chromatography in combination with chemiluminescence detection (CL-HPLC). Mono-OOH was the major species (96% of total hydroperoxides) in trioleoylglycerol [peroxide value (PV) 0.16 meq/kg], and Bis-OOH and Tris-OOH showed prolonged accumulation with photooxidation. This profile was confirmed in photooxidation of trilinoleoylglycerol and trilinolenoylglycerol. Soybean oil (PV 6 meq/kg) contained Mono-OOH oleoyl-linoleoyl-linoleoylglycerol as the main peroxidic molecular species (50% of total hydroperoxides). Mono-OOH trilinoleoylglycerol was the principal species (61% of total hydroperoxides) in safflower oil (PV 5 meq/kg), and Mono-OOH oleoyl-oleoyl-linoleoylglycerol was the representative species (66% of total hydroperoxides) in olive oil (PV 3 meq/kg). The CL-HPLC method, which is specific for the detection of hydroperoxides, should prove useful in studies of triacylglycerol oxidation in foods and vegetable oils.