Nano-enabled-fortification of salad dressings with curcumin: Impact of nanoemulsion-based delivery systems on physicochemical properties

Abstract

Abstract The impact of curcumin-loaded nanodroplets on the properties of commercial salad dressings was examined. Nanoemulsions were formulated using a plant-based oil (medium chain triglycerides, MCT) and either a plant-based (Quillaja saponaria, QS) or animal-based (whey protein isolate, WPI) emulsifier. Curcumin-loaded nanoemulsions produced by microfluidization contained small anionic oil droplets: d32\xa0=\xa00.28 and 0.11\xa0μm and ζ\xa0=\xa0−45 and −42 mV for QS and WPI, respectively (pH 7). The dressing contained larger oil droplets (d32\xa0=\xa07.8\xa0μm) with a lower negative charge (ζ\xa0=\xa0−23\xa0mV). The ζ-potential of the dressing was positive under acid and negative under neutral conditions, suggesting the oil droplets were coated by proteins. At pH 3.4, adding QS-nanoemulsions to the dressing reduced the positive charge, but adding WPI-nanoemulsions increased it. The presence of the nanoemulsions decreased the mean particle diameter of the dressing. Incorporation of nanoemulsions (0–30\xa0g/100\xa0g) reduced the viscosity of the dressings, probably because of the reduction in fat content and ability of small oil droplets to get between larger ones. Finally, incorporation of curcumin-loaded nanoemulsions gave the dressings a strong orange/yellow color (negative a*, positive b*) due to selective light absorption by curcumin.