Furthermore, just after the homogenization, low viscosity fluids were obtained with water and soybean oil with lecithin, with Newtonian behavior at 30:70 ratio and shear-thinning at 60:40 W:O ratio. Those fluids were unstable and phase separated. In one day, the systems presented yield stress and higher apparent viscosity. That characterizes the formation of a gel network, which was intensified along the observation time.
On the other hand, the water–soybean oil system with Span 80, mainly at 60:40 W:O ratio, presented yield stress and high apparent viscosity just after the homogenization. The systems presented Bingham plastic and HB fluid behavior at 30:70 and 60:40 W:O ratios, respectively. After one day, at 30:70 ratio, the rheological characteristics practically did not change with time. At 60:40, the apparent viscosity at 3 s−1 decreased, probably due to a change into a weaker structure.
The water–hexadecane emulsions presented a shear–thinning behavior in most of the conditions, except at 30:70 W:O ratio using lecithin as emulsifier, which showed a Newtonian behavior. The shear–thinning behavior indicates that the droplets of water formed in the hexadecane are affected by the shear deformation. Most of the emulsions presented lower apparent viscosity than the water–soybean oil systems, since the viscosity of pure hexadecane (0.003 Pa s) is lower than that of soybean oil (0.050 Pa s) and no structured system was formed. Most of the samples showed an increase in the apparent viscosity after one day because of the oil phase separation. The exceptions were the PGPR and Span 80 emulsions at 60:40 W:O ratio, which were the most stable among the hexadecane systems