After the 14-day storage, each oil–surfactant combination resulted in products with distinct appearance. Those prepared with PGPR were a homogeneous liquid. Similar aspect was observed in all water–hexadecane systems. However, the water–soybean oil emulsions with Span 80 or lecithin showed a gel-like structure. In the Span 80 system at 60:40 W:O ratio the structure was a firmer gel (Table 1).
The emulsions produced with PGPR and soybean oil were the most stable, resulting in low SI at both W:O ratios through the whole observation time (Table 1, Fig. 6a). The systems with Span 80 and soybean oil presented a faster phase separation followed by a tendency to stabilize with time. The phase separation was more accentuated at 30:70 than at 60:40 W:O ratio. In turn, lecithin emulsions produced with soybean oil showed slower phase separation rate than emulsions with Span 80, mainly at 30:70 W:O ratio. However, differently from Span 80 emulsions, the phase separation in lecithin systems did not stabilize with time. In the last observation day, the 30:70 sample had higher SI than the equivalent Span 80 system (Table 1). Moreover, at 60:40 W:O ratio, the separation of the aqueous phase indicated that lecithin could not stabilize the water droplets, oppositely to PGPR and Span 80, which showed higher stability in emulsions at higher water content.