Physical properties and lipid bioavailability of nanoemulsion-based matrices with different thickening agents

This work studies the influence of two thickening agents, starch and carboxymethyl cellulose (CMC) with different structural characteristics on physical properties and lipid bioavailability of avocado oil-based nanoemulsions. Eight nanoemulsions were prepared varying oil content (5 and 15%) and thickener type and concentration (CMC: 0.5-0.75%; Starch: 6-8%). Particle size (PS) and zeta potential (ZPot) depended mainly on the thickener type; starch-based nanoemulsions showed a lower PS and ZPot values near to zero. Nanoemulsions containing the highest oil (15%) and thickener concentrations (0.75% CMC or 8% starch) were more viscous and pseudoplastic than those with 5% oil. With respect to physical stability, the CMC-thickened nanoemulsions exhibited a better stability than starch-based samples. Starch-based nanoemulsions with 15% oil showed the highest creaming index values (40-45%) after 21 days of storage. In turn, the hydrocolloid type had a significant (p < 0.05) effect on lipid bioavailability of O/W nanoemulsions. Nanoemulsions with 5% and 15% oil did not show significant differences on the digestion rate due to thickener type. However, nanoemulsions with 15% oil presented lower digestion rates and final extent of free fatty acids released, with a lag time increased. At 15% oil, CMC-based nanoemulsions showed a lower release of free fatty acids after lipolysis than starch-thickened samples, indicating that CMC caused physical retention of oil droplets in the matrix structure, delaying lipid digestion. (C) 2017 Elsevier Ltd. All rights reserved.