Prooxidative and antioxidative effects of phospholipids on milk fat

Physical and Oxidative Stability of Flaxseed Oil-in-Water Emulsions Fabricated from Sunflower Lecithins: Impact of Blending Lecithins with Different Phospholipid Profiles

There is great interest in the formulation of plant-based foods enriched with nutrients that promote health, such as polyunsaturated fatty acids. This study evaluated the impact of sunflower phospholipid type on the formation and stability of flaxseed oil-in-water emulsions. Two sunflower lecithins (Sunlipon 50 and 90) with different phosphatidylcholine (PC) levels (59 and 90%, respectively) were used in varying ratios to form emulsions. Emulsion droplet size, charge, appearance, microstructure, and oxidation were measured during storage at 55 °C in the dark. The physical and chemical stability increased as the PC content of the lecithin blends decreased. The oxidative stability of emulsions formulated using Sunlipon 50 was better than emulsions formulated using synthetic surfactants (SDS or Tween 20). The results are interpreted in terms of the impact of emulsifier type on the colloidal interactions between oil droplets and on the molecular interactions between pro-oxidants and oil droplet surfaces.

Influence of casein-phospholipid combinations as emulsifier on the physical and oxidative stability of fish oil-in-water emulsions

The objective of this study was to investigate the influence of casein (0.3% w/w) and phospholipid (0.5% w/w) emulsifier combinations on the physical and oxidative stability of 10% fish oil-in-water emulsions at pH 7. For that purpose, three phospholipids were evaluated, namely, lecithin (LC), phosphatidylcholine (PC), and phosphatidylethanolamine (PE). The emulsion stabilized with LC showed the best physical stability having the most negative zeta potential and the lowest mean droplet size. In addition, this emulsion was also the least oxidized in terms of peroxide value and concentration of the volatile oxidation product 1-penten-3-ol. This finding is not explained by the antioxidant activity of LC because it showed similar DPPH scavenging activity and lower metal chelating activity than the other phospholipids. Therefore, these results suggested that other factors such as the combination of casein and lecithin, which could result in a favorable structure and thickness of the interfacial layer, prevented lipid oxidation in this emulsion.

Singlet oxygen quenching effects of phosphatidylcholine in emulsion containing sunflower oil

Effects of phosphatidylcholine (PC) on the oxidation of oil by singlet oxygen in a W/O microemulsion and an emulsion food model containing tocopherol-stripped sunflower oil (TSSO) have been studied. The W/O microemulsion consisted of methylene chloride, butanol, and sodium dodecyl sulfate with PC (0, 250, 1000 ppm) and TSSO (0, 3.3, 16.5, 33 mg/mL). Production of singlet oxygen in the microemulsion was done chemically with hydrogen peroxide in the presence of sodium molybdate, and indirectly evaluated by rubrene oxidation at A529. The emulsion food model consisted of TSSO, distilled water, and xanthan gum with addition of 250 ppm PC and 4 ppm chlorophyll b, and was placed at 25 degrees C under fluorescent lights (1700 lux) for 24 h. The oxidation of TSSO was determined by thin-layer chromatography and values of conjugated dienoic acid (CDA) and peroxides (POV). PC significantly decreased the oxidation of rubrene and TSSO in the W/O microemulsion, but its content was decreased to approximately one-half by a 20-min reaction, indicating its degradation. This clearly shows that PC acted as an antioxidant via chemical quenching of singlet oxygen in the W/O microemulsion. A possible synergism between PC and TSSO was observed in singlet oxygen quenching in the microemulsion. PC also significantly decreased the chlorophyll-photosensitized oxidation of TSSO in the emulsion food model, possibly by singlet oxygen quenching. This study clearly suggested that PC be used as an antioxidant to improve the lipid oxidative stability of an emulsion food containing chlorophyll under light.