The effect of soybean lecithin addition on the iron-catalyzed or chlorophyll-photosensitized oxidation of emulsions consisting of purified canola oil and water (1:1, w/w) was studied based on headspace oxygen consumption using gas chromatography and hydroperoxide production using the ferric thiocyanate method. Addition levels of iron sulfate, chlorophyll, and soybean lecithin were 5, 4, and 350 mg/kg, respectively. Phospholipids (PLs) during oxidation of the emulsions were monitored by high performance liquid chromatography. Addition of soybean lecithin to the emulsions significantly reduced and decelerated iron-catalyzed oil oxidation by lowering headspace oxygen consumption and hydroperoxide production. However, soybean lecithin had no significant antioxidant effect on chlorophyll-photosensitized oxidation of the emulsions. PLs in soybean lecithin added to the emulsions were degraded during both oxidation processes, although there was little change in PL composition. Among PLs in soybean lecithin, phosphatidylethanolamine and phosphatidylinositol were degraded the fastest in the iron-catalyzed and the chlorophyll-photosensitized oxidation, respectively. The results suggest that addition of soybean lecithin as an emulsifier can also improve the oxidative stability of oil in an emulsion.

The effects of addition of soy‐derived phosphatidylcholine (PC), phosphatidylethanolamine (PE), or phosphatidylinositol (PI) and the contribution of their structural segment during iron‐catalyzed autoxidation of canola oil in a water/oil (W/O) (1:1, w/w) emulsion were studied by headspace oxygen consumption using gas chromatography and hydroperoxide production by the ferric thiocyanate method. The phospholipid content was monitored by high performance liquid chromatography. Addition of PC and PE significantly (p < 0.05) improved the oxidative stability of the oil in the emulsion by decelerating headspace oxygen consumption and hydroperoxide production, with the PC having higher antioxidant effect. All phospholipids were degraded during autoxidation of the emulsion, with higher sensitivities of the PE and PC than the PI. Among the structural segments, ethanolamine and phosphoric acid significantly contributed to the antioxidant activity, while inositol showed little effect. Linoleic acid and choline showed the highest antioxidant activity at 350 mg/kg. The results suggest that hydrogen donation and a physical barrier to oxygen contribute to the antioxidant activity of PE and PC in the W/O emulsion, respectively.

Lipid oxidation and antioxidants changes in perilla oil emulsion added with chlorophyll were studied during storage in the dark or under 1,700 lux light at 25℃ for 48 h. The emulsion was consisted of perilla oil (33.12 g), 5% acetic acid (66.23 g), egg yolk powder (0.5 g), and xanthan gum (0.15 g), and Chlorophyll b was added to the emulsion at 0, 2.5 and 4 mg/kg. The lipid oxidation was evaluated by headspace oxygen consumption and hydroperoxide formation, and tocopherols and polyphenols were monitored by HPLC and spectrophotometry at 725 nm, respectively. The lipid oxidation of the perilla oil emulsion in the dark was not significant regardless of the addition of chlorophyll. Light increased and accelerated the lipid oxidation of the emulsion, and increased addition level of chlorophyll under light increased it further. However, there was no significant change in fatty acid composition in any case. Contents of tocopherols and polyphenols in the emulsion were not significantly changed during storage in the dark regardless of chlorophyll addition, indicating their little degradation. Tocopherols and polyphenols in the emulsion were significantly degraded during storage of the emulsion under light, and the degradation rate of polyphenols was increased with addition level of chlorophyll. The lipid oxidation of the perilla oil emulsion was inversely related with the residual amounts of tocopherols and polyphenols, with more dependent on the retention of polyphenols than that of tocopherols.

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