Nanoemulsions fabricated from food-grade ingredients are being increasingly utilized in the food industry to encapsulate, protect, and deliver lipophilic functional components, such as biologically-active lipids (e.g., ω-3 fatty acids, conjugated linoleic acid) and oil-soluble flavors, vitamins, preservatives, and nutraceuticals. The small size of the particles in nanoemulsions (r<100 nm) means that they have a number of potential advantages over conventional emulsions-higher stability to droplet aggregation and gravitational separation, high optical clarity, ability to modulate product texture, and, increased bioavailability of lipophilic components. On the other hand, there may also be some risks associated with the oral ingestion of nanoemulsions, such as their ability to change the biological fate of bioactive components within the gastrointestinal tract and the potential toxicity of some of the components used in their fabrication. This review article provides an overview of the current status of nanoemulsion formulation, fabrication, properties, applications, biological fate, and potential toxicity with emphasis on systems suitable for utilization within the food and beverage industry.

Food-grade nanoemulsions: formulation, fabrication, properties, performance, biological fate, and potential toxicity.

Amyloid or amyloid-like fibrils represent a general class of nanomaterials that can be formed from many different peptides and proteins. Although these structures have an important role in neurodegenerative disorders, amyloid materials have also been exploited for functional purposes by organisms ranging from bacteria to mammals. Here we review the functional and pathological roles of amyloid materials and discuss how they can be linked back to their nanoscale origins in the structure and nanomechanics of these materials. We focus on insights both from experiments and simulations, and discuss how comparisons between functional protein filaments and structures that are assembled abnormally can shed light on the fundamental material selection criteria that lead to evolutionary bias in multiscale material design in nature.

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Nanomechanics of functional and pathological amyloid materials

Self-assembled peptide and protein amyloid nanostructures have traditionally been considered only as pathological aggregates implicated in human neurodegenerative diseases. In more recent times, these nanostructures have found interesting applications as advanced materials in biomedicine, tissue engineering, renewable energy, environmental science, nanotechnology and material science, to name only a few fields. In all these applications, the final function depends on: (i) the specific mechanisms of protein aggregation, (ii) the hierarchical structure of the protein and peptide amyloids from the atomistic to mesoscopic length scales and (iii) the physical properties of the amyloids in the context of their surrounding environment (biological or artificial). In this review, we will discuss recent progress made in the field of functional and artificial amyloids and highlight connections between protein/peptide folding, unfolding and aggregation mechanisms, with the resulting amyloid structure and functionality. We also highlight current advances in the design and synthesis of amyloid-based biological and functional materials and identify new potential fields in which amyloid-based structures promise new breakthroughs.

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Self-assembling peptide and protein amyloids: from structure to tailored function in nanotechnology

The aggregation of proteins is central to many aspects of daily life, including food processing, blood coagulation, eye cataract formation disease and prion-related neurodegenerative infections(1-5). However, the physical mechanisms responsible for amyloidosis-the irreversible fibril formation of various proteins that is linked to disorders such as Alzheimer's, Creutzfeldt-Jakob and Huntington's diseases-have not yet been fully elucidated(6-9). Here, we show that different stages of amyloid aggregation can be examined by performing a statistical polymer physics analysis of single-molecule atomic force microscopy images of heat-denatured beta-lactoglobulin fibrils. The atomic force microscopy analysis, supported by theoretical arguments, reveals that the fibrils have a multistranded helical shape with twisted ribbon-like structures. Our results also indicate a possible general model for amyloid fibril assembly and illustrate the potential of this approach for investigating fibrillar systems.

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Understanding amyloid aggregation by statistical analysis of atomic force microscopy images

Solid particles of nanoscale and microscale dimensions are becoming recognized for their potential application in the formulation of novel dispersed systems containing emulsified oil or water droplets. This review describes developments in the formation and properties of food-grade emulsion systems based on traditional edible dispersed particles (fat crystals), commercial nanoparticles (silica nanoparticles), and novel particles of biological origin (starch microparticles, chitin nanocrystals). The special features characterizing the properties of particle-stabilized droplets are highlighted in comparison with those of conventional protein-stabilized emulsions. Complexities arising from synergistic interactions of particles with other surface-active ingredients are discussed.

Use of nanoparticles and microparticles in the formation and stabilization of food emulsions

https://doc.rero.ch/record/10758/files/mezzenga_shi.pdf

Structure of Heat-Induced β-Lactoglobulin Aggregates and their Complexes with Sodium-Dodecyl Sulfate

Interfacial properties of native β-lactoglobulin monomers and their heat-induced fibers, of two different lengths, were investigated at pH 2, through surface tension measurements at water-air and water-oil interfaces and interfacial shear rheology at the water-oil interface. The applied heat treatment generates a mixed system of fibers with unconverted monomers and hydrolyzed peptides. The surface tension of this system at the water-air interface decreased more rapidly than the surface tension of native monomers, especially at short times (10(-3) to 10(2) s). This behavior was not observed when the unconverted monomers and peptides were removed by dialysis. At the water-oil interface, the adsorption kinetics was much faster than at the water-air interface, with a plateau interfacial pressure value reached after 1 h of adsorption. For all the systems, interfacial shear rheology showed the formation of a highly elastic interface, with solid-like behavior at 1-10(3) s time scales. The highest modulus was observed for the long fibers and the lowest for the native monomers. Creep-compliance curves in the linear regime could be reduced to a single master curve, showing similar spectra of relaxation times for all investigated systems. Upon large deformations, the interfaces formed with long fibers showed the most rigid and fragile behavior. This rigidity was even more pronounced in the presence of unconverted monomers.

https://doc.rero.ch/record/21696/files/jun_iai.pdf

Interfacial Activity and Interfacial Shear Rheology of Native β-Lactoglobulin Monomers and Their Heat-Induced Fibers

We have developed a new method allowing the study of the thermodynamic phase behavior of mesoscopic colloidal systems consisting of amyloid protein fibers in water, obtained by heat denaturation and aggregation of beta-lactoglobulin, a dairy protein. The fibers have a cross section of about 5.2 nm and two groups of polydisperse contour lengths: (i) long fibers of 1-20 microm, showing semiflexible behavior, and (ii) short rods of 100-200 nm long, obtained by cutting the long fibers via high-pressure homogenization. At pH 2 without salt, these fibers are highly charged and stable in water. We have studied the isotropic-nematic phase transition for both systems and compared our results with the theoretical values predicted by Onsager's theory. The experimentally measured isotropic-nematic phase transition was found to occur at 0.4% and at 3% for the long and short fibers, respectively. For both systems, this phase transition occurs at concentrations more than 1 order of magnitude lower than what is expected based on Onsager's theory. Moreover, at low enough pH, no intermediate biphasic region was observed between the isotropic phase and the nematic phase. The phase diagrams of both systems (pH vs concentration) showed similar, yet complex and rich, phase behavior. We discuss the possible physical fundamentals ruling the phase diagram as well as the discrepancy we observe for the isotropic-nematic phase transition between our experimental results and the predicted theoretical results. Our work highlights that systems formed by water-amyloid protein fibers are way too complex to be understood based solely on Onsager's theories. Experimental results are revisited in terms of the Flory's theory (1956) for suspensions of rods, which allows accounting for rod-solvent hydrophobic interactions. This theoretical approach allows explaining, on a semiquantitative basis, most of the discrepancies observed between the experimental results and Onsager's predictions. The sources of protein fibers complex colloidal behavior are analyzed and discussed at length.

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Liquid Crystalline Phase Behavior of Protein Fibers in Water: Experiments versus Theory

We investigate the effects of variable linear charge density and Debye length on the mesoscopic properties of β-lactoglobulin fibers in water, by changing the pH and ionic strength, respectively. W...

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Jin-Mi Jung

Papers

Understanding amyloid aggregation by statistical analysis of atomic force microscopy images

Structure of Heat-Induced β-Lactoglobulin Aggregates and their Complexes with Sodium-Dodecyl Sulfate

Interfacial Activity and Interfacial Shear Rheology of Native β-Lactoglobulin Monomers and Their Heat-Induced Fibers

Liquid Crystalline Phase Behavior of Protein Fibers in Water: Experiments versus Theory

Effects of charge double layer and colloidal aggregation on the isotropic-nematic transition of protein fibers in water.