Lipid oxidation emulsion droplet membrane

Relationships between emulsion droplet membrane thickness and iron-promoted lipid oxidation... 

Lipid oxidation in multiphase systems is greatly influenced by the nature of the interface, which in turn is affected by the composition of the oil, the water phases and surface-active solutes. In foods the membranes surrounding the emulsion droplets consist of surface-active substances or proteins or both. In addition to enhancing the physical stability of emulsion droplets, the film or membrane surrounding the droplets affect lipid oxidation processes in many ways. 

The interfacial thickness of emulsion droplets is an important parameter affecting lipid oxidation reaction rates. Increasing interfacial membrane thickness can conceivably hinder the physical interaction between aqueous phase prooxidants (e.g., transition metals) and emulsified lipids(Chaiyasit et al., 2000 Silvestre et al., 2000). For example, Silvestre and co-workers (2000) showed that iron-catalyzed cumenehydroperoxide reduction, as well as salmon oil-in-water emulsion oxidation, was slower when Brij 700 was used in place of Brij 76. Brij 700 and 76 are small molecule surfactants with identical hydrophobic tail group lengths (CHjlCH lj -), but vary only with respect to the size of their polar head groups Brij 700 and Brij 76 consist of 100 and 10 oxyethylene head groups, respectively. Lower hydroperoxide decomposition and lipid oxidation rates in Brij 700-stabilized emulsions suggest that a thicker interfacial layer was able to act as a physical barrier to decrease lipid-prooxidant interactions (Silvestre et al., 2000). 

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