**2.5. Chemical stability of lutein in the emulsion**

The chemical stability of lutein was assessed by measuring the concentration of lutein in the lutein-enriched emulsions during storage at 5 and 15°C and analyzed right after production (0 day) and at 1, 2, 4, 6, and 7 days. The concentration of lutein was determined from absorbance measurements at 460 nm using a Beckman UV/visible model DU-530 spectrophotometer (Beckman Instruments Inc., Fullerton, CA, USA). To prepare the samples for the spectrophotometric measurements, the lutein-enriched emulsions were diluted 100 times in DMSO (50 μl of emulsion was diluted into 4.95 ml of DMSO). The DMSO was used because it dissolves lutein, oil, lecithin, and protein to form transparent solutions suitable for UV/ visible analysis. The emulsion without lutein was used as a blank. A calibration curve was constructed by dissolving lutein standards in DMSO within a range from 0.5 to 5 mg/ml.
