Synergistic Solubilization of Mixed Nutraceuticals in Modified Discontinuous Micellar Cubic Structures - Food Colloids: Self-Assembly and Material Science - page 91

pertinent DSC peak. The DSC temperatures reported here were reproducible
to 0.51C.
6.3 Results and Discussion
6.3.1 Thermal Behaviour of the Q L Phase
A typical DSC thermogram of the first heating scan of the frozen GMO +
water + ethanol mixture (pre-cooled to 101C) reveals the existence of three
endothermic events at 0.26, 6.0 and 19.321C (Figure 2). The endothermic peak
at 0.261C is partially overlapped by a large endothermic peak (as indicated by
an asterisk in the thermogram) and so is difficult to resolve. This endotherm
corresponds to the thawing of free water. The existence of this free water was
confirmed by replacing H 2 O with D 2 O, which resulted in an endotherm shift of
2.741C (not shown). The endotherm is small, even at 50-wt% water content,
with a melting enthalpy of only 5.16 10 2 Jg 1 . The small enthalpy
involved in the thawing process means that most of the water is bound to the
lipid and alcohol, and that only minor amounts remain as free water.
The second event, appearing at 6.01C, has a DH value of 15.91 J g 1 . This
endothermic event corresponds to a typical L b L a phase transition. Usually,
the L b phase is formed under intermediate conditions between the crystalline
state and the more fluid mesophases, particularly where the crystal structure
itself consists of parallel stacks of bilayers. 1 Formation of the L b phase can be
further confirmed by the SAXS and WAXS synchrotron measurements. The
analysis of the reciprocal spacing of SAXS data in this temperature range
(0-61C) reveals diffractogram peaks typical of L b with a 1:2 ratio of first and
second diffraction orders. The d-spacing of L b is 49.6 A ˚ , in good agreement
with the previously reported values. 32,33 The WAXS results show five sharp
peaks, cooperative with a broad peak centred at 4.611 A ˚ 1 [Figure 3(a)]. These
Figure 2 Typical DSC thermogram of the first scan following heating of the Q L phase.
Enthalpy change D H is plotted against temperature. The shoulder at position *
is explained in the text