Jiyeun Lee

Effects of phosphatidylcholine and phosphatidylethanolamine on the photooxidation of canola oil.

Effects of chlorophyll b, phosphatidylcholine (PC), and phosphatidylethanolamine (PE) on the oxidation of canola oil under 1700 lux light at 10 degrees C were studied by determining the headspace oxygen depletion and peroxide value. Chlorophyll b increased the oil oxidation under light via production of singlet oxygen. PC and PE did not affect the headspace oxygen depletion and peroxide formation in the oil in the absence of chlorophyll b at 10 degrees C; however, they increased in the presence of chlorophyll, with higher effect of PC than PE. Chlorophyll was degraded during the oil photooxidation and PC and PE decreased its photodecomposition with higher protection by PC than PE. There was no effect of light or singlet oxygen on PC and PE during the oil photooxidation. The results clearly showed that PC and PE were prooxidants in the photooxidation of canola oil containing chlorophyll b by protecting it from photodecomposition, and thus PC and PE should be removed from the oil containing chlorophyll to improve the photooxidative stability.

Effects of phospholipids on the antioxidant activity of α-tocopherol in the singlet oxygen oxidation of canola oil

This study evaluated the effects of phosphatidylcholine (PC) or phosphatidylethanolamine (PE) on the antioxidative activity of α-tocopherol during oxidation of canola oil by singlet oxygen at 10°C for seven hours. Singlet oxygen was produced by chlorophyll b (4 ppm) under 1,700 lux. The oxidation of oil was evaluated by headspace oxygen consumption by gas chromatography and peroxide values (POVs). Concentrations of PC, PE, chlorophyll, and α-tocopherol were determined by HPLC. PC and PE protected chlorophyll from degradation, but they accelerated the degradation of α-tocopherol under singlet oxygen. Contents of PC and PE did not change for seven hours under singlet oxygen. α-Tocopherol significantly lowered POV and headspace oxygen consumption of canola oil under singlet oxygen, and its antioxidant activity was increased by the co-presence of PC and PE. PC and PE increased chemical quenching of singlet oxygen by tocopherol in decreasing the oil oxidation.

Effects of Chlorophyll and Carotene on Lipid Oxidation and Tocopherols during Heating for Manufacturing of Perilla and Rice Porridge

The effects of chlorophyll (0.33 mg/kg) and β-carotene (3.3, 9.9, 19.8 mg/kg) addition to a mixture of roasted perilla seeds, rice, and water (30:45:225, w/w/w) on the lipid oxidation and tocopherol contents were studied during heating at 100 o C for 120 min to simulate cooking of perilla and rice porridge. Lipid oxidation was evaluated with peroxide values (POV) and conjugated dienoic acid (CDA) values, and chlorophyll, β-carotene, and tocopherols were determined by HPLC, POV, and CDA values were increased during heating, indicating the occurrence of lipid oxidation in the perilla and rice porridge. β-Carotene decreased the POV and CDA values of the samples in a concentration-dependent manner, while the addition of chlorophyll did not affect them. Chlorophyll and β-carotene which were added, and tocopherols naturally present in samples were degraded, following the first order kinetics during heating, and β-carotene protected tocopherols from degradation.