Synergistic Solubilization of Mixed Nutraceuticals in Modified Discontinuous Micellar Cubic Structures - Food Colloids: Self-Assembly and Material Science - page 94

based on a hydrated N-monomethylated dioleoylphosphatidyl ethanolamine
system.
6.3.2 Systems Loaded with Phytosterols
The main purpose of this set of experiments was to determine the effect of
added guest nutraceutical molecules such as phytosterols on the integrity of the
Q L mesophase, and to detect any phase transformation that might occur as a
result of the incorporation of the lipophilic guest molecules.
Samples loaded with phytosterols at several solubilization capacities were
tested for their thermal behaviour. Figure 5 shows DSC measurements carried
out using the same thermal protocol on samples containing 0.2, 1.4 and 2.5
wt% phytosterols. All the samples were liquid, optically isotropic and com-
pletely transparent; and no phytosterol crystals were detected, meaning that all
the added phytosterol was fully solubilized within the mesophase. The DSC
measurements were carried out with the same heating protocol as that of the
unloaded (control) Q L sample. The enthalpy values of all the endothermic
events occurring in the control sample and in the presence of increasing
amounts of solubilized phytosterols are summarized in Table 1. The thermo-
grams of the heating scans revealed that the temperature of the L b -L a phase
transition almost did not shift: the endothermic events occurred at 6.04, 5.66,
5.63 and 5.681C for increasing amounts of solubilized phytosterols. Yet the
magnitude of the enthalpy of transformation was found to decrease substan-
tially with increase in the phytosterol content. The effect of phytosterols on the
L a -Q L transition enthalpies is also significant, although the transition temper-
ature did not change. The enthalpy change was larger for 0.2-wt% phytosterols
( 1.24 J g 1 ), but it decreased with increased content of phytosterols above
0.2 wt%. The sharp drop in the transition entropy indicates that the phase is
almost completely disordered in the presence of a high concentration of
solubilized phytosterols.
Figure 5 The heating curve from the DSC thermograms carried out on samples containing
various concentrations of phytosterols: (a) 0 wt%, (b) 0.2 wt%, (c) 1.4 wt%
and (d) 2.5 wt%. Enthalpy change D H is plotted against temperature