Microstructure
Micrographs were obtained with a polarized light filter (10X objective),
where the birefringence of the structures formed by the MY is present
(Fig. 6). More crystalline structures were found in the SAT systems.
This is due to the fact that a higher concentration of MY provides more
nucleation points from which the formation of fibrillar crystalline
structures occurs, which in turn form the three-dimensional network that
immobilizes the liquid oil. Gelator saturation in SAT systems affects
the crystalline units in oleogels, this can trigger a decrease in their
structural integrity in the initial crystallization process, due to the
increased nucleation-crystallization rate, resulting in lower nvalues due to the formation of individual crystal lattices (Table 4).
This can be understood as a constraint on network structuring, since
individual networks will exhibit less bonding between their structures
in the long term. The nucleation rate is closely related to the number
of structural elements in an oleogel.
In Figure 6, a higher degree of structuring is observed in CN systems,
because the presence of MY promotes early crystallization of the oil at
ambient temperature, even at low concentrations (MGC). A better
distribution of crystalline structures throughout the plane can be
beneficial to obtain desired solid properties, however, an
oversaturation of the same can also result in a high hardness and
brittle system. From an image analysis, fractal dimensionality values
were determined by the correlation method (FD) with high
R2 values (Table 4). Fractal dimensionality is an
index that points out the crystalline mass distribution in the lattice
of an oleogel. All systems present ≈2 values, it is worth mentioning
that the geometry of a growing crystal is not determinant of its
dimensionality due to the fact that nucleation can be homogeneous or
heterogeneous. The DF values reported here are lower than those reported
by Palla et al. (2019), with a saturated monoglyceride concentration in
a high oleic oil. Differences can be found between the Avrami and FD
values of n (Table 4). The geometrical growth of a crystalline
structure, in turn, is not independent of the MY concentration, since a
higher concentration of gelator in a mostly saturated solvent promotes
heterogeneous crystallization from the first structures formed also
inducing the sporadic generation of new nucle.