Chemistry Reference
In-Depth Information
Figure 6 The cooling 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
Table 2 Transition enthalpy change
D
H, transition point temperature and
transition temperature range of the endothermic events occurring on
cooling of the control samples and in the presence of increasing
quantities of solubilized phytosterols
D
H(Jg
1
)
Temperature (1C)
L
a
L
b
L
a
L
b
(1.14-2.70)
a
Q
L
1.03
2.03
b
(1.63-2.81)
a
Q
L
+ 0.2-wt% phytosterols
1.18
2.10
b
(1.68-3.91)
a
Q
L
+ 1.4-wt% phytosterols
0.91
2.94
b
(1.77-4.62)
a
Q
L
+ 2.5-wt% phytosterols
0.70
3.09
b
a
Range of peak.
b
Centre of peak.
detected. It should be also stressed that the intensities of the SAXS diffrac-
tions were more pronounced.
Once a higher quantity (2.5 wt%) of phytosterols had been solubilized, the
SAXS diffraction again became less pronounced and a clear loss of peak
resolution was observed. Figure 7 shows that the peaks have profiles similar to
those of an empty blank sample of the Q
L
phase, but with lower intensity (64%
for the blank system of the Q
L
phase and 53% for the enriched Q
L
phase with
2.5 wt% solubilized phytosterols). Four diffraction peaks with d-spacing ratios
of
O
2:
O
5:
O
8:
O
9 can be attributed to a cubic symmetry, but the peaks are
insufficiently well resolved to identify precisely the symmetry of the cubic
phase. We can provide a possible explanation for this behaviour: high levels of
solubilized phytosterols cause structural defects in the cubic phase due to the
differences in molecular size and packing between GMO and phytosterols
which affects the inner order once the levels of added phytosterol become
significant.
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