Berlin 2015 – wissenschaftliches Programm
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 75: Physics of Food (joint session CPP, BP)
CPP 75.1: Vortrag
Donnerstag, 19. März 2015, 18:00–18:15, C 264
Small-angle scattering study on the structure of the lecithin stabilizer layer in tetracosane-water nanoemulsions and -suspensions — •Martin Schmiele and Tobias Unruh — Physik Department, Friedrich-Alexander-Universität Erlangen–Nürnberg, Staudtstr. 3, 91058 Erlangen, Germany
Tetracosane (C24, TCS) o/w nanoemulsions stabilized by the lecithin 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) were prepared by high-pressure melt homogenization. The droplets (diameters of about 65 nm as measured by photon correlation spectroscopy) exhibit a strong super-cooling (Δ T about 20 K) and crystallize in a for TCS unusual orthorhombic crystal structure (space group Pca21 as verified by wide-angle x-ray scattering).
Using small-angle x-ray and neutron scattering and nanodispersions with different neutron scattering contrasts for the TCS core and the DMPC stabilizer layer, the molecular arrangement of DMPC in the interfacial layer was studied. For the nanoemulsions a dense monolayer of DMPC with a thickness of about 16.2 Å was found with only a minor interpenetration between TCS and the acyl chains of DMPC. For the nanosuspensions a monolayer thickness of 10.5 Å is found, indicating a more flat arrangement of the DMPC molecules at the interface. This could be explained by the expanded surface of the nanocrystals with respect to the emulsion droplets.
The structure of the interfacial stabilizer layer of lipid emulsions and suspensions is highly relevant with regard to lipid oxidation of bioactive compounds in food and the crystallization of nanoemulsions.