Lutein-enriched emulsion-based delivery systems: Influence of pH and temperature on physical and chemical stability

• Lutein emulsion-based delivery systems were prepared from all-natural ingredients.
• Elevated temperatures promoted rapid degradation of lutein leading to color fading.
• The activation energy for the chemical degradation of lutein was 38 kJ/mol.
• Lutein chemical stability was not strongly influenced by storage pH.
• Emulsion physical stability was affected by storage pH and not by temperature.

Lutein may be utilized in foods as a natural pigment or nutraceutical ingredient to improve eye health. Nevertheless, its use is limited by its poor water-solubility and chemical instability. We evaluated the effect of storage temperature and pH on the physical and chemical stability of lutein-enriched emulsions prepared using caseinate. The emulsions (initial droplet diameter = 232 nm) remained physically stable at all incubation temperatures (5–70 °C); however the chemical degradation of lutein increased with increasing temperature (activation energy = 38 kJ/mol). Solution pH had a major impact on the physical stability of the emulsions, causing droplet aggregation at pH 4 and 5. Conversely, the chemical stability of lutein was largely independent of the pH, with only a slight decrease in degradation at pH 8. This work provides important information for the rational design of emulsion-based delivery systems for a lipophilic natural dye and nutraceutical.