Antioxidant role of DOPC in stripped soybean oil-in-water emulsion as related to pH and DOPC concentration

Antioxidant role of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) was studied in stripped soybean oil-in-water emulsions. To determine how DOPC influences the oxidation of oil-in-water emulsions, different concentrations of DOPC (0.0003, 0.003, 0.03, 0.3 mmol/kg oil) were added to Tween 20-stabilized stripped soybean oil-in-water emulsions at pH 7.0 and 3.0 and several physico-chemical parameters were evaluated. Addition of different levels of DOPC to the emulsions at neutral pH decreased lipid hydroperoxides and headspace hexanal formation. No significant changes on the size and surface charge of the emulsion droplet were observed with increasing DOPC concentration, suggesting that DOPC phosphate groups did not migrate and concentrate at the lipid-water interface of the emulsion droplet. At pH 3, a lower ability of DOPC to reduce lipid oxidation was evinced, as higher hydroperoxide and hexanal concentrations were found with respect to those of the control emulsion. It might be possible that, at pH 7.0, DOPC was able to change the physical properties of the emulsion droplets in a manner that increased oxidative stability, which might be related to its ability to form structures within the lipid phase of the emulsions droplets, thus reducing lipid oxidation.