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Optimization of the fabrication, stability, and performance of food grade nanoemulsions with low and high energy methods

There is interest in the production of emulsions by low-energy methods because no expensive equipment is required thus making emulsion formation inexpensive and simple to implement. The goal of this research is to establish the major factors that affect emulsion formation using low-energy methods and possible applications of the emulsions and nanoemulsions formed by this method. Lastly, the use of natural emulsifiers with low- and high-energy methods was investigated. Initially, formation of nanoemulsions using isothermal low energy methods was investigated with a model system (hexadecane, Brij 30). Preliminary experiments showed that nanoemulsions could only be formed when the surfactant was initially mixed in with the oil phase. The major factors that affected particle size included order of addition, surfactant concentration, and storage temperature, while addition rate and stirring speed had minimal effects. The optimal formulation conditions were determined to be at a surfactant-to-oil ratio (SOR) of 0.375, an addition time of 5 minutes, and a stir speed of 700 rpm for both spontaneous emulsification and emulsion phase inversion methods. Additionally, emulsions could be stored for up to a month at temperatures less than 25°C without showing any instability. Experiments were then carried out to establish which factors affect nanoemulsion formation when using food grade ingredients and the spontaneous emulsification method. Droplet size decreased with increasing SOR and was smallest when the non-ionic surfactant Tween 80 was utilized. In order for spontaneous emulsification to occur, the surfactant had to be initially dissolved in the organic phase rather than the aqueous phase. Oil composition affected particle size with medium chain triglycerides (MCT) forming the smallest droplets followed by flavor oils and then long chain triglycerides forming the largest droplets. However, no physiochemical correlation could be made between oil characteristics and particle size. The results obtained using spontaneous emulsification were then compared to those obtained using emulsion phase inversion and similarities were found, implying a common underlying mechanism for the two methods. Next, the formation of nanoemulsions using the spontaneous emulsification method was demonstrated in a model food system: a gelatin-based dessert. The influence of preparation and storage conditions on nanoemulsion formation and stability were investigated. Droplet size decreased with increasing preparation temperature. Translucent filled hydrogels could be formed by incorporating nanoemulsions into the gelatin system. Optical and rheological properties remained unchanged with emulsion incorporation into a model gelatin gel and commercial gelatin dessert. The use of spontaneous emulsification to produce nanoemulsions may be helpful in the production of functional food gels. Finally, sunflower phospholipids were investigated as an emulsifier using spontaneous emulsification. Initial particle diameter was influenced by phospholipid composition, phospholipid concentration, initial phospholipid location, and storage time. Relatively large emulsion droplets (d > 10 mm) could be formed which means it is possible to form emulsions using natural emulsifiers when fine droplets are not essential. However, often fine droplets are more desirable so the use of sunflower phospholipids with the high energy method of microfluidization was also investigated to see if an w-3 fatty acid nanoemulsion delivery system could be formed. Relatively small droplets (d < 150 nm) could be formed by optimizing the phospholipid type and concentration. These results suggest that sunflower phospholipids are a viable emulsifier choice to form nanoemulsions and have added benefits due to their low allergenicity and non-genetically modified sources.
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