Thin liquid films stabilized by plant proteins: Implications for foam stability.

Hypothesis: Plant-based proteins offer a sustainable solution for stabilizing multiphase food materials like edible foams and emulsions. However, challenges in understanding and engineering plant protein-stabilized interfaces persist, mostly because of the commonly poorer functionality and complex composition of the respective protein isolates. We hypothesize that part of the limited understanding is related to the lack of experimental data on the length-scale of the thin liquid film that separates two neighboring bubbles.

The role of oleosins and phosphatidylcholines on the membrane mechanics of oleosomes.

Hypothesis: Oilseeds use triacylglycerides as main energy source, and pack them into highly stable droplets (oleosomes) to facilitate the triacylglycerides' long-term storage in the aqueous cytosol. To prevent the coalescence of oleosomes, they are stabilized by a phospholipid monolayer and unique surfactant-shaped proteins, called oleosins. In this study, we use state-of-the-art interfacial techniques to reveal the function of each component at the oleosome interface.

Impact of Deformability and Rigidity of Starch Granules on Linear and Non-Linear Rheological Behavior of Waxy Rice Starch Gels and Applicability for Food End Uses.

The objective of this study was to investigate granule size and distribution and deformability of granules and their effect on the rheological properties of waxy starch gels. Native (granular) waxy rice gels (10%) were prepared, and their response in oscillatory shear was investigated in the linear and non-linear viscoelastic regime. The results show the gels were mainly composed of aggregated and deformed swollen granules.

Ion-Induced Reassembly between Protein Nanotubes and Nanospheres.

Proteins used as building blocks to template nanostructures with manifold morphologies have been widely reported. Understanding their self-assembly and reassembly mechanism is important for designing functional biomaterials. Herein, we show that enzyme-hydrolyzed α-lactalbumin (α-lac) can self-assemble into either nanotubes in the presence of Ca ions or nanospheres in the absence of Ca in solution.

Molecular structure and linear-non linear rheology relation of rice starch during milky, dough, and mature stages.

Immature rice has potential to be used as healthy food. The relation between molecular structure and rheological properties was investigated. The lamellar repeating distance (8.

Surface stress decomposition in large amplitude oscillatory interfacial dilatation of complex interfaces.

Hypothesis: Multiphase materials are often subjected to large deformations during processing, but the rheological responses of complex interfaces (e.g. stabilized by proteins) in this nonlinear deformation regime are still poorly understood.

Pasting and Rheological Properties of Starch Paste/Gels in a Sugar-Acid System.

This study was to investigate the impact of granule size, amylose content, and starch molecular characteristics on pasting and rheological properties of starch paste/gels in neutral (water) and sugar-acid systems. Normal rice starch (RS), waxy rice starch (WRS), normal tapioca starch (TS), and waxy tapioca starch (WTS) representing small-granule starches and intermediate-granule starches respectively, were used in the study. Impacts of granule size, AM content, and their synergistic effects resulted in different starch susceptibility to acid hydrolysis and interactions between starch and sucrose-water, yielding different paste viscosities in both systems.

Impact of Particle Sedimentation in Pendant Drop Tensiometry.

Understanding the interface-stabilizing properties of surface-active components is key in designing stable macroscopic multiphase systems, such as emulsions and foams. When poorly soluble materials are used as an interface stabilizer, the insoluble material may sediment and interfere with the analysis of interfacial properties in pendant (or hanging) drop tensiometry. Here, the impact of sedimentation of particles on the interfacial properties determined by pendant drop tensiometry was evaluated using a model system of whey protein isolate and (non surface-active) glass beads (2.

Non-linear rheology reveals the importance of elasticity in meat and meat analogues.

The interest in plant-based meat analogues as an alternative to meat is currently growing. Rheological benchmarking is used to reveal how closely meat analogues resemble the original meat products. Texture maps and dissipation colour schemes were used to reveal similarities in and differences between rheological responses of meat and meat analogues (especially chicken analogues).

Air-water interfacial behaviour of whey protein and rapeseed oleosome mixtures.

Hypothesis: Plant seeds store lipids in oleosomes, which are storage organelles with a triacylglycerol (TAG) core surrounded by a phospholipid monolayer and proteins. Due to their membrane components, oleosomes have an affinity for the air/oil-water interface. Therefore, it is expected that oleosomes can stabilise interfaces, and also compete with proteins for the air-water interface.

Large amplitude oscillatory shear (LAOS) for nonlinear rheological behavior of heterogeneous emulsion gels made from natural supramolecular gelators.

The linear and nonlinear rheological behaviors of heterogeneous emulsions gels made from natural glycyrrhizic acid (GA) nanofibrils and sitosterol-oryzanol mixtures (sterols) were investigated using small amplitude oscillatory shear (SAOS) and large amplitude oscillatory shear (LAOS). The nonlinear rheological response was qualitatively analyzed using normalized Lissajous-Bowditch curves. The microstructure of the emulsion gels strongly depended on the concentration of sterols in the oil phase, and showed a percolated segregated network at 10-20 wt% sterols due to the partial coalescence of droplets, and a jamming transition without coalescence at higher sterols concentration of 30 wt%.

Adsorption of rapeseed proteins at oil/water interfaces. Janus-like napins dominate the interface.

Plants offer a vast variety of protein extracts, typically containing multiple species of proteins that can serve as building blocks of soft materials, like emulsions. However, the role of each protein species concerning the formation of emulsions and interfaces with diverse rheological properties is still unknown. Therefore, deciphering the role of the individual proteins in an extract is highly relevant, since it determines the optimal level of purification, and hence the sustainability aspects of the extract.

Interfacial rheology and relaxation behavior of adsorption layers of the triterpenoid saponin Escin.

Hypothesis: Escin, a monodesmosidic triterpenoid saponin, was shown previously to form viscoelastic interfaces with a very high dilatational and surface shear storage modulus. This is expected to be due to the arrangement of Escin into 2D disordered soft viscoelastic solid interfacial structures, which results in turn in a distribution of relaxation times.

Experiments: The responses to dilatational and surface shear deformations of Escin-stabilized air-water interfaces were studied, both in the linear viscoelastic (LVE) and non-linear (NLVE) regime.

Relaxation Behavior and Nonlinear Surface Rheology of PEO-PPO-PEO Triblock Copolymers at the Air-Water Interface.

Surface dilatational viscoelasticity of adsorbed layers of pluronics triblock copolymers at the air-water interface was measured using the oscillating barrier technique. The effect of molecular architecture and concentration on surface viscoelasticity was explored for two different types of pluronics with different degrees of hydrophobicity, Pluronic F-108 ( ≈ 14 600 g/mol) and Pluronic P-123 ( ≈ 5800 g/mol), the former exhibiting a larger hydrophilic to hydrophobic block length ratio. Frequency sweeps in the linear regime suggested that interfacial films of F-108 have higher surface limiting elasticity and larger in-plane and out-of-plane relaxation times at the same bulk concentration (the former possibly related to in-plane microstructure rearrangements, the latter to surface/bulk diffusion).

Dynamic heterogeneity in complex interfaces of soft interface-dominated materials.

Complex interfaces stabilized by proteins, polymers or nanoparticles, have a much richer dynamics than those stabilized by simple surfactants. By subjecting fluid-fluid interfaces to step extension-compression deformations, we show that in general these complex interfaces have dynamic heterogeneity in their relaxation response that is well described by a Kohlrausch-Williams-Watts function, with stretch exponent β between 0.4-0.

Gas-liquid phase equilibrium of a model Langmuir monolayer captured by a multiscale approach.

The gas-liquid expanded phase transition of a Langmuir monolayer happens at very low surface concentrations which makes this phenomenon extremely expensive to explore in finite three-dimensional (3D) atomistic simulations. Starting with a 3D model reference system of amphiphilic surfactants at a 2D vapor-liquid interface, we apply our recently developed approach (Phys. Chem.

Self-assembly of ellipsoidal particles at fluid-fluid interfaces with an empirical pair potential.

Colloidal particles adsorbed at fluid-fluid interfaces interact via mechanisms that can be specific to the presence of interfaces, for instance, lateral capillary interactions induced by nonspherical particles. Capillary interactions are highly relevant for self-assembly and the formation of surface microstructures, however, these are very challenging to model due to the multibody nature of capillary interactions. This work pursues a direct comparison between our computational modelling approach and experimental results on surface microstructures formed by ellipsoidal particles.

Modifying the Contact Angle of Anisotropic Cellulose Nanocrystals: Effect on Interfacial Rheology and Structure.

Cellulose nanocrystals (CNCs) are an emerging natural material with the ability to stabilize fluid/fluid interfaces. Native CNC is hydrophilic and does not change the interfacial tension of the stabilized emulsion or foam system. In this study, rodlike cellulose particles were isolated from hemp and chemically modified to alter their hydrophobicity, i.

Contribution of Long Fibrils and Peptides to Surface and Foaming Behavior of Soy Protein Fibril System.

When soy glycinin (11S) is heated for a prolonged time at pH 2 (20 h at 85 °C), a mixture is formed consisting of long semiflexible 11S fibrils and small peptides. The surface and foaming properties of this mixture were investigated at different pHs, and compared to the behavior of pure fibrils and pure peptides, to determine the individual contributions of these two factions to the behavior of the mixture. The adsorption of these three systems at air-water interfaces and the resulting surface rheological properties were studied by combining drop shape analysis tensiometry, ellipsometry, and surface large amplitude oscillatory dilatational (LAOD) rheology.