Interfacial engineering using mixed protein systems: emulsion-based delivery systems for encapsulation and...

Emulsion-based delivery systems are needed to encapsulate, protect, and deliver lipophilic bioactive components in the food, personal care, and pharmaceutical industries. The functional performance of these systems can be controlled by engineering the composition and structure of the interfacial layer coating the lipid droplets. In this study, interfacial properties were controlled using two globular proteins with widely differing isoelectric points: lactoferrin (LF: pI ≈ 8.5) and β-lactoglobulin (BLG: pI ≈ 5). Oil-in-water emulsions were prepared with different interfacial properties: [LF]-only; [BLG]-only; [LF]-[BLG]-(laminated); [BLG]-[LF]-(laminated); and [BLG/LF]-(mixed). The influence of pH, ionic strength, and temperature on the physical stability of β-carotene-enriched emulsions was investigated. [LF]-emulsions were stable to droplet aggregation from pH 2 to 9 (0 mM NaCl), but all other emulsions aggregated at intermediate pH values. [BLG]-emulsions aggregated at high salt levels (≥50 mM NaCl), but all other emulsions were stable (0 to 300 mM NaCl). [BLG/LF]-emulsions were unstable to heating (≥60 °C), but all other emulsions were stable (30 to 90 °C). Color fading due to β-carotene degradation occurred relatively quickly in [BLG]-emulsions (37 °C) but was considerably lower in all other emulsions, which was attributed to the ability of LF to bind iron or interact with β-carotene. This study provides useful information for designing emulsion-based delivery systems to encapsulate and protect bioactive lipids, such as carotenoids.