**2.3. Emulsion preparation**

A corn oil-in-water emulsion was prepared as follows: an organic phase was prepared by diluting 2.5% (wt/wt) of the commercial lutein in corn oil. Soybean lecithin 0.5% (wt/wt) was dissolved in the corn oil. An aqueous phase was prepared by dispersing 1.0% (wt/ wt) of lyophilized bovine casein or caprine casein into the aqueous buffer solution (5 mM phosphate, pH 7.0). A coarse emulsion of oil-in-water was prepared by mixing the organic phase (10%, wt/wt) and the aqueous phase (90%, wt/wt) using a hand-held homogenizer (Biospec Products, Inc., Bartlesville, OK, USA) at low speed. The coarse emulsion was then homogenized five times at 82.74 MPa (12,000 psi) through a high-pressure TC5 homogenizer (Stansted Fluid Power, Harlow, UK). The fine emulsion produced was then diluted (1:1, v/v) with buffer solution containing an antimicrobial agent [5 mM phosphate buffer at pH 7.0 and 1 mM (wt/v) thimerosal]. The final diluted emulsions that were used for the stability studies contained 5% (wt/wt) oil phase and 250 mg per liter of lutein. Resulting emulsions were stored in the dark at 5 and 15°C for 7 days.
