Lutein-enriched emulsion-based delivery systems: Impact of Maillard conjugation on physicochemical stability and gastrointestinal fate

• Casein-dextran conjugates were formed using the Maillard reaction.
• Lutein-enriched emulsions were stabilized by casein or casein-dextran conjugates.
• Maillard conjugation inhibited isoelectric flocculation of casein-coated droplets.
• Maillard conjugation did not inhibit color fading due to lutein degradation.
• The use of Maillard conjugates did not affect lutein bioaccessibility.

The utilization of lutein as a natural colorant or nutraceutical in many foods, supplements, and other commercial products is currently limited because of its low water-solubility and chemical instability. The purpose of this study was to evaluate the effect of Maillard conjugates on the physical and chemical stability of lutein-enriched emulsions exposed to different temperatures and pH values, as well as on their potential gastrointestinal fate. Oil-in-water emulsions were prepared using either casein or casein-dextran conjugates as emulsifiers. Both types of emulsions showed a slight increase in particle aggregation at temperatures exceeding 37 °C, and became more prone to color fading (lutein degradation) as the temperature was increased. Casein-coated oil droplets were highly unstable to flocculation near their isoelectric point (pH 4–5) due to the reduction in electrostatic repulsion. However, casein-dextran-coated droplets were stable from pH 3 to 7, which was attributed to strong steric repulsion by the dextran moiety. The casein-coated droplets were unstable to aggregation in the gastric phase of the simulated GIT, whereas the casein-dextrin-coated ones were stable, which was again attributed to increased steric repulsion. Emulsifier type did not strongly influence lutein bioaccessibility. This work shows that Maillard conjugates can improve the physical stability of lutein-enriched emulsions without adversely affecting the bioaccessibility of the bioactive agent.

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