Development of food grade O/W nanoemulsions as carriers of vitamin D for the fortification of emulsion based food matrices: A structural and activity study

Abstract

Oil-in-water (O/W) edible nanoemulsions were developed and studied as carriers of vitamin D (D3: cholecalciferol) to be used for the fortification of dairy emulsions. The nanoemulsions were produced using polysorbate 20, soybean lecithin and their mixtures as emulsifiers. The dispersed oil phase consisted of either soybean oil or mixtures of the oil with cocoa butter. Coarse emulsion premixes were passed through high pressure homogenizer (800–1000 bar) to produce fine droplets. The influence of system composition and preparation conditions on the stability of the nanoemulsions was investigated using Dynamic Light Scattering (DLS). Nanoemulsions containing oil droplets with mean diameters <200 nm and narrow particle size distributions (PdI < 0.3) were obtained. Different concentrations of vitamin D3 ranging from 0.1 to 0.5 μg/mL were encapsulated in the oil cores of selected stable nanoemulsions and their physical stability was evaluated by the maintenance of size distribution for several weeks. Interfacial properties of empty and vitamin enriched nanoemulsions were studied using Electron Paramagnetic Resonance (EPR) spectroscopy and an amphiphilic spin probe. Spin probe's mobility was decreased upon increase of systems complexity and also the presence of vitamin D3. Moreover, partial vitamin's embedment in the interface thus rendering it more fluid was evidenced in systems stabilized by polysorbates. Finally, whole-fat milk was fortified with the aforementioned vitamin enriched nanoemulsions and remained stable to particle growth and gravitational separation for at least ten days. Antiradical properties of encapsulated cholecalciferol were investigated using an EPR approach.