Delivering β-carotene from O/W emulsion-based systems: Influence of phase ratio and carrier lipid composition

The functional performance of emulsified delivery systems depends on the nature of the ingredients, emulsifier type, bioactive compound, droplet volume fraction, and interfacial tension between the oil and aqueous phases. In this context, this study evaluated the effect of β-carotene incorporation in oil-in-water (O/W) emulsions with different volume fractions of the dispersed phase (20, 40 and 60%) assessing the characteristics and in vitro digestibility of these emulsions, using palm or sunflower oil as the oil phase. The presence of the bioactive compound did not influence the rheological behavior of the emulsions, which presented Newtonian fluid behavior. However, emulsions showed higher mean droplet size with adding β-carotene and increasing the O/W ratio. In general, systems with a higher O/W ratio (40:60 and 60:40) showed excellent kinetic stability due to the limitation of droplet movement caused by the high viscosity, regardless of the oil type. Overall, palm oil emulsions showed better characteristics as delivery systems, such as smaller droplet size, better stability, and less color change after 7 days of storage than sunflower oil emulsions. Furthermore, a higher release of free fatty acids from palm oil emulsions was observed, indicating a more significant action of lipase and bile salts at the droplet interface during in vitro digestion. However, sunflower oil emulsion showed a higher bioaccessibility of β-carotene than those incorporated in palm oil one since the fat crystal network inside the palm oil droplets slowed down the β-carotene diffusion from the droplet core to the interface during the digestion process.