Application of flow cytometry as novel technology in studying lipid oxidation and mass transport phenomena in oil-in-water emulsions.

Flow cytometry was used to determine if lipid oxidation products could transfer between individual emulsion droplets. Medium chain triacyclglycerol oil-in-water emulsions containing an oxidizable fluorescent dye, BODIPY^665/676, was blended with a soybean oil-in-water emulsion. Results showed that when the concentration of sodium dodecyl sulfonate (SDS) were lower than critical micelle concentration (CMC), lipid oxidation products of triacylglycerols were not able to escape out until emulsions were extremely oxidized. With surfactant micelles, oxidation of BODIPY^665/676 was observed. In the presence of free fatty acids, the transfer of prooxidants between droplets was observed even when surfactant concentration was lower than CMC. The decomposition product, 2,4,-decadienal, was also found to be transferred between droplets. The effect of surfactant concentration on prooxidant transfer was investigated using the lipid-soluble radical generator, AMVN. Results showed that surfactants promoted AMVN-triggered degradation of fluorescence at low concentrations but inhibited degradation at high concentration. The CMC of SDS was decreased by NaCl thus affecting the transfer phenomenon. With flow cytometry, the phenomenon of mass transfer between individual droplets was revealed which provides a better understanding of lipid oxidation in emulsion system.