Transparent Dispersions of Milk Fat-Based Solid Lipid Nanoparticles for Delivery of beta-Carotene

Solid lipid nanoparticles (SLNs) are a category of delivery systems applicable to various bioactive compounds in the food industry. Compared to conventional emulsions that have a fluidic oil phase, the mobility and release of bioactive compounds can be controlled by encapsulation in the solid lipid matrix with appropriate properties. Common approaches of preparing SLNs are high energy methods and solvent evaporation methods, which have can lead to degradation of compounds during processing and residues of organic solvent, respectively. In this thesis, a low energy approach based on the phase inversion temperature method has been used to prepare SLNs based on anhydrous milk fat (AMF). Food grade surfactant Tween 80 was used as a surfactant, and beta-carotene was used as a model lipophilic bioactive compound. AMF and surfactant solution with 0-1.0 M NaCl were mixed to form coarse emulsions that were heated at 80-95 °C [Celsius degree] for 30 min to induce phase inversion, followed by a fast cooling process in ice bath. The phase inversion temperature decreased from >95 °C to 73°C when NaCl increased from 0 to 1.0 M in the aqueous phase. Up to 10% w/w of AMF can be encapsulated in the system as transparent dispersions, with particle mean diameter smaller than 25 nm. The SLN dispersions were dilution and dialysis stable, and the particle size and turbidity maintained unchanged during the 90-day storage at room temperature. Compared with beta-carotene encapsulated in soybean oil-based nanoemulsion, degradation of beta-carotene in SLNs was much reduced. The studied SLNs may find unique applications in incorporating lipophilic bioactive compounds in transparent beverages.