Preparation and characterization of nanoemulsions stabilized by food biopolymers using microfluidization

Emulsions are widely used in beverage products and typically impart cloudiness to the beverage. Nanoemulsions have the potential to provide a transparent appearance to the beverage. The objective of the present study was to investigate the formation of nanoemulsions using food biopolymers and its potential for clear beverage applications. The biopolymers chosen for study were Gum Arabic (GA), modified gum arabic (MGA), whey protein isolate (WPI) and modified starch (Purity Gum 2000, MS). Weighted orange oil terpenes (OT) and medium chain triglycerides (MCT) were used as the dispersed phase. Nanoemulsions were characterized by dynamic light scattering (DLS), cryogenic scanning electron microscopy (Cryo-SEM) and turbidimeter. Except for the WPI stabilized nanoemulsions, higher homogenization pressures (up to 22 000 psi) and a greater number of passes (up to 7) through a Microfluidizer® produced nanoemulsions with a smaller mean droplet diameter in volume (MDD, d_V). MS showed the best performance of the food biopolymers resulting in a MDD as small as 77 nm and a corresponding turbidity of 72 NTU (Nephelometric Turbidity Units) at 0.05% of the dispersed phase, whereas GA produced emulsions with the largest MDD. The MDD of MS stabilized nanoemulsions decreased with increasing MS concentrations (from 5 to 25 wt %). The effect of oil types on MDD was complex being dependent on the emulsifier and homogenization pressure. Turbidity of diluted nanoemulsions increases with MDD within the range of 70-300 nm. This study shows food biopolymers can be used to produce nanoemulsions using microfluidization under a high pressure. It was also demonstrated that nanoemulsions with a MDD < 100 nm can provide a clear appearance in beverage applications. The results provide an understanding of how manufacturing parameters and formulation influence the formation of nanoemulsions.