Hydration behavior of casein micelles in thin film geometry: a GISANS study?

Small-Angle Neutron Scattering Study of High Fat Fish Oil-In-Water Emulsion Stabilized with Sodium Caseinate and Phosphatidylcholine

We report on small-angle neutron scattering (SANS) investigations of separate phase domains in high fat (70%) oil-in-water emulsions emulsified with the combination of sodium caseinate (CAS) and phosphatidylcholine (PC). The emulsion as a whole was studied by contrast variation to identify scattering components dominated by individual emulsifiers. The emulsion was subsequently separated into the aqueous phase and the oil-rich droplet phase, which were characterized separately. Emulsions produced with 1.05% (w/w) CAS and PC fraction which varies between 1.75% (w/w) and 0.35% (w/w) provided droplets between 10 and 19 μm in surface weighted mean in 70% fish oil-in-water emulsions. At least two-third of the overall CAS is associated with the interface, while the rest remains with the aqueous phase. Six percent of PC formed a monolayer in the interface, while the rest of the PC remains in the droplet phase in the form of multilayers. When the separated components were resuspended, the resuspended emulsion showed similar characteristics compared to the original emulsion in terms of droplet size distribution and neutron scattering. Instead, CAS in the aqueous phase separated from the emulsion shows aggregation not present in the corresponding CAS-in-D₂O system.

Water ingress into a casein film quantified using time-resolved neutron imaging

The migration of water into a casein film was probed with neutron radiography. From the neutron transmission images, the evolution of the water saturation profiles was extracted. The results indicate that the water influx is dominated by imbibition but also contains a diffusional component. The time dependence of the water ingress was quantified using a diffusion-like equation previously also applied to imbibition. A water transport coefficient D = 0.9 × 10(-9) m(2) s(-1) was found. This value and direct observation of the images indicate that the time taken for a typical adhesive casein-based layer to become saturated with water is of the order of hours.

The structure of the casein micelle of milk and its changes during processing

The majority of the protein in cow's milk is contained in the particles known as casein micelles. This review describes the main structural features of these particles and the different models that have been used to define the interior structures. The reactions of the micelles during processing operations are described in terms of the structural models.

AFM imaging of milk casein micelles: evidence for structural rearrangement upon acidification

Milk casein micelles are natural association colloids that we all encounter in everyday life, yet we still lack an accurate description of their internal structure and the interactions that stabilize it. In this letter, we provide for the first time detailed images of intact casein micelles as obtained through atomic force microscopy under liquid conditions close to physiological. The micelles appear as heterogeneous raspberry-like particles, which is consistent with a hierarchical/spongelike structure made of connected 10-40 nm dense casein regions. Upon in situ acidification to pH 5, the micelles decrease in size and lose their surface heterogeneities, indicating that this structure is highly sensitive to variations in mineral content and caseins net charge.

Phase Separation and Molecular Intermixing in Polymer-Fullerene Bulk Heterojunction Thin Films

The phase separation and molecular intermixing in poly(3-hexylthiophene) (P3HT)/[6,6]-phenyl-C61 butyric acid methyl ester (PCBM) bulk heterojunction thin films are investigated as a function of the overall PCBM content. The structural length scales, phase sizes, and molecular miscibility ratio in bulk heterojunction films are probed with grazing incidence small-angle neutron scattering (GISANS). The PCBM content is varied between 9 and 67 wt %. For the symmetric P3HT/PCBM ratio, which is typically highly efficient in photovoltaic devices, a structure size of 20 nm, the largest PCBM phases, and 18 vol % dispersed PCBM in the amorphous P3HT phase are found. The molecularly dispersed PCBM content is found to increase with the overall PCBM content. Absorption measurements complement the GISANS investigation.

How to squeeze a sponge: casein micelles under osmotic stress, a SAXS study

By combining the osmotic stress technique with small-angle x-ray scattering measurements, we followed the structural response of the casein micelle to an overall increase in concentration. When the aqueous phase that separates the micelles is extracted, they behave as polydisperse repelling spheres and their internal structure is not affected. When they are compressed, the micelles lose water and shrink to a smaller volume. Our results indicate that this compression is nonaffine, i.e., some parts of the micelle collapse, whereas other parts resist deformation. We suggest that this behavior is consistent with a spongelike casein micelle having a triple hierarchical structure. The lowest level of the structure consists of the CaP nanoclusters that serve as anchors for the casein molecules. The intermediate level consists of 10- to 40-nm hard regions that resist compression and contain the nanoclusters. Those regions are connected and/or partially merged with each other, thus forming a continuous and porous material. The third level of structure is the casein micelle itself, with an average size of 100 nm. In our view, such a structure is consistent with the observation of 10- to 20-nm casein particles in the Golgi vesicles of lactating cells: upon aggregation, those particles would rearrange, fuse, and/or swell to form the spongelike micelle.