3.1. Bigel Appearance
The successfully prepared bigel samples were evaluated based on their
appearance after gelation. Bigels were classified as successful if they
were opaque, white and showed no signs of phase separation. Fig. 1 shows
the 60:40 and 70:30 OG:HG bigel formulations cut into a cylinder shape.
80:20 OG:HG formulations (not shown) could not be stabilized and showed
phased separation immediately after preparation despite the addition of
MDG. For this reason, 80:20 OG:HG were excluded from further testing.
Most of the formulations for 60:40 and 70:30 OG:HG were successful with
the exception of 70:30(3) as can be observed in Fig. 1. The 70:30(3)
bigel formulation resulted in phase separation, whereas the control,
70:30(0), showed excellent physical stability. With an increase in MDG
concentration, going from 0% to 3%, the bigel became more malleable
for both 60:40 and 70:30 OG:HG ratios. The presence of MDG creates a
softer, more pliable bigel without altering the visual appearance from
the control and without the use of a large amount of hydrogel which can
be beneficial for applications where more lipidic phase is desirable.
The fact that MDG creates a softer, more malleable bigel may be
attributed to MDG being a known lipid modifier (Ribeiro et al., 2015;
Alfutimie et al., 2016). It can be hypothesized that MDG may have a dual
effect on the bigel system, serving as both a lipid modifier in the
lipid phase and an emulsifier at the aqueous-lipid interface.