Oxidation mechanisms in real food emulsions : Method for separation of mayonnaise by ultracentrifugation

With the aim of studying partition coefficients of antioxidants and secondary oxidation products in a real food emulsion a method,for the separation of mayonnaise was developed. The method included freezing and a mild precentrifugation step followed by ultracentrifugation at 197,500 x g. The precentrifugation separated most of the oil (96%) from the rest of the mayonnaise. The ultracentrifugation separated the remaining fraction into four phases: a small oil phase constituting 0.25% of the total, a relatively small emulsion phase (approximately 5% w/w), an almost translucent aqueous phase that constituted the largest fraction (88%, w/w), and lastly a precipitate (6%, w/w). The objective of the present investigation was to test the efficiency of the method to separate a hydrophobic compound, the methyl ester of C23:0, and a hydrophilic compound, NaCl. The oil soluble compound (C23:0) was almost completely recovered (96%) in the oil phase after the preseparation step, whereas the water soluble compound (NaCl) was almost completely recovered (86%) in the aqueous Chase obtained after ultracentrifugation. This investigation thus demonstrated that the separation method may be useful in studies concerning partition coefficients of antioxidants and secondary lipid oxidation products