Preparation and characterization of patauá and pracaxi Brazilian vegetable oil emulsions

Abstract

In this work, the stability of oil-in-water emulsions (O/W) of patauá (Oenocarpus bataua) and pracaxi (Pentaclethra macroloba) oils, both from Amazon rainforest, was investigated. Low-energy emulsification methods were used, such as Emulsion Inversion Point (EIP) and Phase Inversion Temperature (PIT), both based on the minimal interfacial surface, combined with optimized Hydrophilic-Lipophilic Balance (HLB). Phase inversion was determined by electrical conductivity measurements. The surfactants used were Span® 80, Tween® 20, Tween® 60, and Tween® 80. Surfactant mixtures of Span® 80 + Tween® 80 were the best samples prepared. The composition of the most stable samples was 80.00 wt% aqueous phase, 15.00 wt% nonionic surfactants, and 5.00 wt% oil phase (patauá or pracaxi oil). The samples with the best kinetic results were those prepared with the required HLB and PIT values of 12.86 and 84.05 °C, for patauá oil, and of 9.61 and 79.50 °C for pracaxi oil. The kinetic stability of the oil emulsions was characterized by creaming index (CI), by evolution over time of the droplet size, viscosity, and electric conductivity. The results showed that: (1) the droplet size distribution influenced electric conductivity; (2) the relative amount of surfactants Tween® and Span® used is more important to determine the physicochemical and interfacial properties of the emulsion than the oil identity itself; (3) it is crucial to pay attention to the influence of air bubbles—involuntarily inserted into the mixture during the emulsification process—in the physicochemical properties of the system. These conclusions can be extended to other oil-in-water emulsions.