Carotenoids encapsulated in natural flaxseed oil body: Different colloidal interfaces induce their behavior and stability disparity

Flaxseed oil bodies (FOBs) are being explored as natural plant-based delivery systems for the encapsulation and delivery of nutrients. However, there is currently a relatively poor understanding of their interfacial interaction and how this impacts delivery systems. In this study, β-carotene and lutein with far different molecular polarity were used to provide insights into their impacts on properties of FOB. In addition to the carotenoids (>93%) embedded and dissolved in the lipid core, they also interacted with the interfacial membrane components to impact the FOB properties. Raman showed the proportion of random coil and β-sheet in FOB-L (hydrophilic domain of interfacial protein) increased by 8% and 5% respectively, but remained almost unchanged in FOB-β, indicating lutein could interact with the polar exterior of interfacial membranes. Consistently, molecular dynamic simulations and spectroscopy analysis showed that lutein containing hydroxyl in β, ε-ionone ring was more likely to approach the outer hydrophilic regions of interfacial protein, while fatty soluble β-carotene interacted with hydrophobic region of inner membrane protein and phospholipid alkyl chain (close to oil). This difference in interfacial interactions induced significant discrepancies in the lipid oxidation, rheological behavior of carotenoid-FOB assemblies. Lutein was located at the outer edge where oxidation begins, making it more effective than β-carotene in improving the lipid oxidation stability of the FOB. Moreover, lutein therefore modulated interactions between oil droplets and altered the rheological properties of the FOB, whereas β-carotene had little effect. This study may facilitate the design of oil bodies-based delivery systems that have improved functional properties.