Preparation of W₁/O/W₂ emulsions and droplet size distribution measurements by pulsed‐field gradient nuclear magnetic resonance (PFG‐NMR) technique

Abstract

manyMultiple emulsions of W 1 /O/W 2 type are of major interest in life sciences, offering possibilities for the encapsulation of water-soluble active agents. In food science, they are also applied for fat reduction. The droplet size distributions of the inner and outer emulsions are of main importance as they influence the rheological and sensorial properties, the release kinetics, as well as the structural and microbial stability. However, the determination of the inner and outer droplet size distributions is a major challenge, as conventional measurement techniques cannot be applied. Pulsed-field gradient nuclear magnetic resonance (PFG-NMR) is well known as a non-destructive tool for droplet size determination, especially in simple emulsions. In this work, double emulsions of the W 1 /O/W 2 type were prepared with polyglycerol-polyricinoleate (PGPR) and polyoxyethylen-20-sorbitan monolaurate (Tween 20) as emulsifiers by means of rotor-stator emulsification machines. PFG-NMR was applied for measurements of the inner phase (W 1 ) droplet size distribution as well as for the characterization of the O phase. The W 1 values were compared with results from laser light diffraction of simple emulsions (W 1 /O type) and were found to be consistent within the experimental errors, if restricted diffusion in the outer water phase (W 2 ) and additional effects are considered.

Detecting diffusion-diffraction patterns in size distribution phantoms using double-pulsed field gradient NMR: Theory and experiments

“…39,40 This major caveat is probably why diffusion-diffractions are not observed in most diffusion NMR studies of neuronal tissue, 1,41,42 broadly distributed emulsions, [43][44][45][46] and other porous media which are characterized by a relatively broad size distribution. In fact, in a recent work, Pages et al 47 showed the reversible loss of diffusion-diffraction minima when RBCs transformed from discocytes ͑relatively monodispere͒ to spherocytes ͑broader size distribution͒.…”

NMR on emulsions: characterisation of liquid dispersed systems

“…9(a). At larger values, the steep decrease is diminished indicating that the two compartment limit is not fully reached, which is also reflected by the increase of d 33 with D (see also Wolf et al [89] ). The noise level has to be considered during fitting because of normalisation of the signal.…”

“…In 2009, the results were confirmed by applying PFG-STE to WOW-double emulsions produced in a two-step procedure. [89] At small g values deviating, but at higher gradient steps parallel signal attenuation of the double emulsion compared with the corresponding single emulsion was found. Molecular exchange between the inner and the outer water phase was supposed to be responsible for the observation.…”

PFG-NMR on Double Emulsions: a Detailed Look into Molecular Processes

“…In several publications, the possibility of molecular exchange in double emulsions is discussed [5][6][7][8][9][10][11][12] . In some publications [8][9][10] , a molecular exchange model was applied, which originally was found to be applicable in case of cellular systems [5][6][7] .…”

“…In some publications [8][9][10] , a molecular exchange model was applied, which originally was found to be applicable in case of cellular systems [5][6][7] . There is, however, some controversy whether such effects are observed or other phenomena are responsible for the experimental results.…”