Ultrasound-assisted oil-in-water nanoemulsion produced using Pereskia aculeata Miller mucilage

Abstract

There is considerable interest from the food industry, pharmaceutical, agrochemical and other segments for the use of colloidal dispersions to encapsulate, protect, and deliver lipophilic bioactive components. In certain applications, it is desirable to use colloidal dispersions containing much smaller droplets, because they have many potential advantages over conventional systems. For the preparation of nanoemulsions, the correct choice of emulsifiers, together with the emulsification methods, directly influences the final product quality. The present study reports the ultrasound-assisted preparation of oil-in-water nanoemulsions produced with mucilage extracted from leaves of Pereskia aculeata Miller (ora-pro-nobis; OPN). The OPN mucilage (%) and soybean oil (%) concentration range, and the process operating parameters, ultrasonic power amplitude (%) and sonication time (min), were optimized based on the mean droplet diameter ( 32 d ). The effect of the mucilage and oil concentrations was also investigated by the response variables such as polydispersity, density, turbidity, viscosity, zeta-potential, and interfacial tension. The higher OPN mucilage concentrations (%) with lower amounts of soybean oil (%) favored nanoemulsion formations (116 ≤ 32 d ≤ 171 nm) and increased polydispersity, density, and zeta-potential. On increasing OPN mucilage and soybean oil the turbidity of the dispersions increased. All colloidal systems showed Newtonian behavior, and the viscosity in the systems increased due to the greater OPN mucilage concentration in the aqueous phase at a certain oil concentration. In addition, lower values of equilibrium interfacial tension were found with increasing OPN mucilage concentrations. Qualitative analysis of system microstructures was also performed via compound labeling using fluorochromes, which evidenced the adsorption of polysaccharide and protein molecules at the oil-water interface. Finally, from the stability test, it can be pointed out that the OPN mucilage concentration should be between 1.0 and 1.5% and the oil concentration should be less than 5%, so that lower 32 d values are maintained over time. Therefore, mucilage extracted from OPN and the ultrasound technique can be used in the preparation of nanoemulsions.