Comparison of modified starch and Quillaja saponins in the formation and stabilization of flavor nanoemulsions

Modified starch (MS) and Quillaja saponins (QS) were compared to fabricate and stabilize orange oil nanoemulsions using microfluidization. Ester gum (EG) was incorporated in the oil phase at variable proportions (0-60%) as Ostwald ripening inhibitor and viscosity modifier. Optimal viscosity ratios of dispersed to continuous phase (ηd/ηc) were identified as 0.8-3.1 and 2.1-3.3 with MS and QS as emulsifier, respectively. QS was found superior to MS in fabricating nanoemulsion with smallest MDD of 69 nm and turbidity of 102 NTU at 0.05% of dispersed phase. With EG incorporated in the oil phase, QS stabilized nanoemulsions were stable during 2 weeks of storage at 23 °C; whereas MS stabilized nanoemulsions showed significant increases in MDD and turbidity. Zeta potential measurements showed QS imparted higher droplet charge (>−20 mV) than MS (<−5 mV) at pH 3.6 indicating MS stabilized nanoemulsions were destabilized by coalescence due to insufficient interfacial charge.