Chemistry Reference
In-Depth Information
(Beer-Sheva, Israel) as powdered material (all trans) containing 67.4% lycopene
and the rest being tomato oleoresins. The phytosterols (Z 97%-free phytoster-
ols, extracted from soybeans) were a gift from ADM Nutraceuticals (Decatur,
IL, USA). The lycopene and phytosterols were used without any further
purification. Analytical grade ethanol (EtOH, purity > 99%) was purchased
from Frutarom (Israel). The water was double distilled.
The samples of Q
L
mesophase were prepared by weighing appropriate
amounts of molten GMO into culture tubes sealed with Viton-lined screw
caps. The lycopene and the phytosterols were melted prior to being added to
the GMO. Once the samples had reached room temperature, the ethanol and
water were added. The clear samples were stored for several days at 251Cto
make sure that no precipitation of the solubilizates occurred. The transparent
samples were analysed by small-angle X-ray scattering (SAXS), synchrotron-
SAXS and differential scanning calorimetry (DSC) as described below.
SAXS measurements were performed using Ni-filtered Cu Ka radiation
(1.540 A
˚
) from an Elliott GX6 rotating anode operating at 1.2 kW. X-ray
radiation was further monochromated and collimated by a single Franks
mirror and then collimated by a series of slits and height limiters. The scattering
profile was measured by a linear position-sensitive detector of the delay line
type; it was stored on a PC as a 256-channel histogram. The sample-to-detector
distance was approximately 48 cm. Each sample was sealed in a glass capillary
tube (diameter 1.5 mm) placed in a thermostatic bath. Measurements were
carried out at 25
0.51C with an exposure time of 1-3 h.
Temperature-dependent synchrotron measurements of SAXS and wide-angle
X-ray scattering (WAXS) combined with DSC were carried out on a modified
Mettler model FP99A-V4.0 (SAXS
WAXS
DSC) at BL-15A Photon Fac-
tory (KEK, Tsukuba, Japan). The X-ray wavelength was 0.15 nm and the beam
size was 500
500 mm at the sample position. The images of SAXS and WAXS
were measured with an X-ray CCD detector coupled with a 230 mm diameter
X-ray image intensifier (XRII), which was set at a distance of 160 mm from the
sample. In addition to a usual beam stop, a small beam stop of 3 mm in
diameter was set at a distance of 35 mm from the sample in order to reduce air
scattering. The samples were sealed in the same cell, and were heated to 401C
and cooled at a rate of 21C min
1
to
201C for 15 min, and then heated to 251C
at a rate of 11C min
1
. The SAXS
WAXS data were recorded at 10 s intervals
with an exposure time of 1.5 s.
Some DSC measurements were carried out on a Mettler Toledo DSC822
instrument. Samples (5-15 mg) were weighed in standard 40 mL aluminium
pans using a Mettler M3 microbalance and immediately sealed by a press. The
samples were rapidly cooled to
101C at pre-determined quenching rates from
ambient to
101C. Each sample remained at this temperature for 20min and
was then heated (from ca.
101C) at 21C min
1
to 401C. The cooling/heating
cycle was repeated twice. An empty pan was used as reference. The fusion
temperatures of the solid components and the total heat transferred in any of
the observed thermal processes were determined. The enthalpy changes, asso-
ciated with thermal transition, were obtained by integrating the area of each
Search WWH ::
Custom Search