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Weiche Materie Poster: Do., 13:00–15:30 D-P339
A simultaneous SWAXS/Shear/DSC study of a lipid model emulsion
Daniel Kalnin 1,4 , Olivier Schafer 2 , Gerard Keller 1 , Heinz Amenitsch 3 ,
Michel Ollivon 1
1 UMR 8612 CNRS, Equipe de Physico-Chimie des Systèmes Polyphasés, 92296
Châtenay-Malabry, France – 2 CRN, Centre de Recherche Nestlé, Vers-Chez-les-Blanc,
1000 Lausanne 26, Switzerland – 3 SAXS-Beamline 5.2, ELETTRA Sincrotrone, Trieste,
34012 Basovizza (TS), Italy – 4 current adress: WUR, Wageningen University and
Research center, Agrotechnology Food Sciences, Physical-Chemistry of Foods Group,
PO Box 8129, 6700 EV Wageningen, The Netherlands; mail : daniel.kalnin@web.de
The influence of shear on crystallization behavior of emulsified triacylglycerols (TAG)
is investigated using a new micro-Couette device consisting of two coaxial quartz capillaries.
The setup allows for simultaneous measurement of thermal and structural
properties of micro samples under shear or in quiescent conditions. Small and wide
angle X-ray diffraction is performed simultaneously with DSC measurements under or
in the absence of shear. A structural study of lipids under shear was undertaken by
Mazzanti et al. focussing on bulk lipids [1]. Hereafter, the crystallization behavior
of a model emulsion consisting of palm oil stabilized with sodium caseinate (SC) is
analyzed. The combination of the thermal and structural measurements allows for
the determination of the molecular packing of lipids[2] even within emulsion droplets.
In quiescent conditions where a detailed study recently showed the influence of the
concentration of an emulsifier of the crystallisation behaviour[3], a lamellar phase of
TAG of 2Lα type crystallizes first showing a d-spacing of 41 ˚A on cooling. Its progressive
transformation through a monotropic phase transition 2Lα 2Lβ is observed
during the subsequent heating. However, under shear conditions, the more stable 2Lβ
lamellar phase crystallizes first but partially with a smaller d-spacing of 37 ˚A. A still
liquid remaining moiety of the roplets crystallizes in the unstable 2Lα, alike in static
conditions. It can be concluded that shear stress favors the formation of more stable
polymorphs within emulsiondroplets of oil in water emulsions.
[1] Mazzanti G. et al.: Modeling phase transitions during the crystallization of a multicomponent
fat under shear, Phys. Rev. E 71(2005) 041607.
[2] Kalnin et al.: Systematic investigation of lard polymorphism using combined DSC
and time-resolved synchrotron X-ray diffraction, Eur. J. Lipid Sci. Technol. 107 (2005)
594-606.
[3] Kalnin, D. et al.: Fat Crystallization in Emulsion: Influence of the emulsifier concentration
on triacylglycerol crystal growth and polymorphism, Cryst. Growth Des.
4, 6 (2004) 1283-1293.