C. Characterization of linseed fish oil emulsions (LSFE)
oxidative stability and structural changes during thermal oxidation,
using H1 LF-NMR energy relaxation time analysis and supportive
methodologies.
LSFE was prepared, as described in the Material and Methods section by
the addition of fish oil rich in the long chain PUFAs EPA and DHA. The
chemical and morphological structure of LSFE is characterized by oil
bodies vesicles with an amphiphilic interface surface and lipophilic
core encapsulating PUFA-rich linseed and fish oil. The1H LF-NMR energy relaxation TD fingerprinting for LSFE
before (T 0) and after thermal oxidation at 55 oC for
96 hours (T 96 h) are shown in Fig. 6.
It is interesting to note that before and after thermal oxidation at 55oC for 96 hours only minimal phase separation could be
observed in the LSFE samples (see supplemental 1). The analysis of Fig.
6 shows that LSFE T 0 h and LSFE T 96 h have similar characteristics
T1 and T2 energy relaxation time
graphics. The 1D T2 energy relaxation time graphics of
LSFE T 0 h and LSFE T 96 h shows fours small peaks corresponding to the
four segmental motions of the PUFA-rich oil molecules within the core of
the oil bodies emulsion and one peak of higher intensity related to the
oil energy relaxation time in the surface of the oil bodies vesicles.
The 2D T1-T2 relaxation time graphics of
LSFE T 0 h and LSFE T 96 h shows small peaks assigned as the PUFA-rich
oil molecules within the OB core and one peak of higher intensity
related to the energy relaxation time in the OB’s vesicle surface.
In Table 5 the T1 and T2 energy
relaxation times values of LSFE T 0 h and LSFE T 96 h are tabulated. It
can be seen that the relaxation time values of T1 and
T2 of the main peak assigned as the vesicles surface are
somewhat lower for LSFE after the thermal oxidation of 96 hours as are
most of the other peaks that could be observed. These data are in the
same general pattern of the results obtained for LSE described above
(Table 3).
Microscopic images of LSFE oil bodies emulsion of non-heated fresh
sample and after 96 h of thermal heating (Fig. 7), show some increase of
oil bodies after the heating period. Interesting to note that in both
cases before and after heating only minimal phase separation could be
observed in the LSFE samples. A similar pattern for LSFE (Table 6), some
increase of droplet particle size distribution from 1374 to 1951 nm for
fresh and heated sample, respectively was obtained. Zeta potential
values were -27.3 and -25.1 mv for the two samples, suggested of a
moderate rate of stability of the emulsion samples. The rate of self
diffusion was slightly reduced from 2.902 to 2.734 10^-9m*m/s,
respectively. All these supportive analyses well correlated with the
T1-T2 energy relaxation time information
obtained from NMR analyses (Fig. 6) that is also summarized in the small
increase of T1/T2 ratio.