The rheology and foamability of crystal-melt suspensions composed of triacylglycerols.

The rheology of triacylglycerol (TAG) crystal-melt suspensions (CMSs) consisting of anhydrous milk fat (AMF), cocoa butter (CB), and palm kernel oil (PKO) as function of crystallization shear rate cryst and crystal volume fraction ΦSFC is investigated by in-line ultrasound velocity profiling - pressure difference (UVP-PD) rheometry. Measurements up to ΦSFC = 8.8% are presented. Below the percolation threshold Φc, no yield stress τ0 is observed and the viscosity η scales linearly with ΦSFC. Above Φc, a non-linear dependency of both τ0 and η as function of ΦSFC is apparent. For AMF and CB, the increase in cryst leads to a decrease in η and τ0 as function of ΦSFC, whereas for PKO based CMSs the opposite is the case. Scanning electron microscopy (SEM) and polarized light microscopy (PLM) relate these rheological findings to the microstructure of the investigated CMSs by taking the effective aspect ratio aeff and the concept of the effective crystal volume fraction ΦeffSFC into account. Foam formation by dynamically enhanced membrane foaming (DEMF) is performed directly after crystallization and reveals that depending on the CMS rheology and crystallite-, crystallite cluster- and crystal floc microstructure, a wide range of gas volume fractions between 0.05-0.6 are achievable.

Crystallization-Induced Network Formation of Tri- and Monopalmitin at the Middle-Chain Triglyceride Oil/Air Interface.

Crystalline glycerides play an important role in the formation of multiphase systems such as emulsions and foams. The stabilization of oil/water interfaces by glyceride crystals has been extensively studied compared to only few studies which have been dedicated to oil/air interfaces. This study investigates the crystallization and network formation of tripalmitin (TP) and monopalmitin (MP) at the middle-chain triglyceride (MCT) oil/air interface. TP crystals were found to crystallize in the bulk before aggregating as large rectangular crystal conglomerates at the MCT oil/air interface. This leads to the slow formation of a plastic deformable, macroscopic crystal layer with high interfacial rheological moduli. MP crystals form directly at the MCT oil/air interface resulting in a comparatively fast formation of an elastic deformable network. Crystals with tentacle-like morphology were found to be responsible for the network elasticity. In this work, we show how interfacial crystallization dynamics and mechanical strength can be linked to the molecular structure and crystallization behavior of glyceride crystals.

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.e., their surface activity, which was demonstrated by surface tension measurements of the particles at the air/water interface. The buildup and mechanical strength of the interfacial structure were investigated using interfacial shear and dilatational rheometry. In contrast to most particle or protein-based interfacial adsorption layers, we observe in shear flow a Maxwellian behavior instead of a glasslike frequency response. The slow and reversible buildup of the layer and its unique frequency dependence indicate a weakly aggregated system, which depends on the hydrophobicity and, thus, on the contact angle of the CNC particles at the air/water interface. Exposed to dilatational flow, the weakly aggregated particles cluster and form compact structures. The interfacial structure generated by the different flow fields is characterized by the contact angle, immersion depth, and layer roughness obtained by neutron reflectometry with contrast variation while the size and local structural arrangement of the CNC particles were investigated by AFM imaging.

The rheology of batch and continuously prepared gluten-free bread dough in oscillatory and capillary shear flow.

Reduced elasticity and high stickiness of gluten-free bread doughs are major issues regarding the industrial breadmaking process. In this work, we compared traditional batch mixing with a revised continuous extrusion process and extensively study the rheological properties of both doughs. Shear viscosities were measured offline with a capillary rheometer and inline at the extruder die over a large range of apparent shear rates. Data were corrected for entrance effects, wall slip and non-Newtonian flow behaviour. Good agreement between inline and offline measured viscosities were supplemented by amplitude and frequency sweep tests. The results highlight that this extrusion process fostered the production of gluten-free bread dough. We demonstrated that extrusion processing support the combined mixing, kneading, and moulding of gluten-free dough in one single unit. This fundamental study linked physical dough characterization with applied engineering and yielded the understanding and processing of corresponding products.

Microfluidic Technique for the Simultaneous Quantification of Emulsion Instabilities and Lipid Digestion Kinetics.

Quantifying the impact of environmental physicochemical changes on the microstructure of lipid delivery systems is challenging. Therefore, we have developed a methodology to quantify the coalescence of oil-in-water emulsion droplets during lipid digestion in situ on a single droplet level. This technique involves a custom-made glass microfluidic platform, in which oil droplets can be trapped as single droplets, or several droplets per trap. The physicochemical environment can be controlled, and droplet digestion, as well as coalescence, can be visualized. We show that the exchange of the physicochemical conditions in the entire reaction chamber can be reached in under 30 s. Microparticle image velocimetry allowed mapping of the flow profile and demonstrated the tuneability of the shear profile in the device. The extraction of quantitative information regarding the physical characteristics of the droplets during digestion was performed using an automated image analysis throughout the digestion process. Therefore, we were able to show that oil-in-water emulsions stabilized by proteins coalesced under human gastric conditions. This coalescence delayed the overall lipid digestion kinetics. The droplets that coalesced during digestion were hydrolyzed 1.4 times slower than individually trapped droplets. Thus, the microstructural evolution of lipid delivery systems is a crucial factor in lipid digestion kinetics. This novel technique allows the simultaneous quantification of the impact that the physicochemical environment has on both the lipid droplet microstructure and the lipid release patterns.

Methods for Generating Highly Magnetically Responsive Lanthanide-Chelating Phospholipid Polymolecular Assemblies.

Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and its lanthanide ion (Ln3+) chelating phospholipid conjugate, 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), assemble into highly magnetically responsive polymolecular assemblies such as DMPC/DMPE-DTPA/Ln3+ (molar ratio 4:1:1) bicelles. Their geometry and magnetic alignability is enhanced by introducing cholesterol into the bilayer in DMPC/Cholesterol/DMPE-DTPA/Ln3+ (molar ratio 16:4:5:5). However, the reported fabrication procedures remain tedious and limit the generation of highly magnetically alignable species. Herein, a simplified procedure where freeze thawing cycles and extrusion are replaced by gentle heating and cooling cycles for the hydration of the dry lipid film was developed. Heating above the phase transition temperature Tm of the lipids composing the bilayer before cooling back below the Tm was essential to guarantee successful formation of the polymolecular assemblies composed of DMPC/DMPE-DTPA/Ln3+ (molar ratio 4:1:1). Planar polymolecular assemblies in the size range of hundreds of nanometers are achieved and deliver unprecedented gains in magnetic response. The proposed heating and cooling procedure further allowed to regenerate the highly magnetically alignable DMPC/Cholesterol/DMPE-DTPA/Ln3+ (molar ratio 16:4:5:5) species after storage for one month frozen at -18 °C. The simplicity and viability of the proposed fabrication procedure offers a new set of highly magnetically responsive lanthanide ion chelating phospholipid polymolecular assemblies as building blocks for the smart soft materials of tomorrow.

Understanding the Enhanced Magnetic Response of Aminocholesterol Doped Lanthanide-Ion-Chelating Phospholipid Bicelles.

Cholesterol (Chol-OH) and its conjugates are powerful molecules for engineering the physicochemical and magnetic properties of phospholipid bilayers in bicelles. Introduction of aminocholesterol (3ß-amino-5-cholestene, Chol-NH2) in bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and the thulium-ion-chelating phospholipid 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA/Tm3+) results in unprecedented high magnetic alignments by selectively tuning the magnetic susceptibility Δχ of the bilayer. However, little is known on the underlying mechanisms behind the magnetic response and, more generally, on the physicochemical forces governing a Chol-NH2 doped DMPC bilayer. We tackled this shortcoming with a multiscale bottom-up comparative investigation of Chol-OH and Chol-NH2 mixed with DMPC. First, simplified monolayer models on a Langmuir trough were employed to compare the two steroid molecules at various contents in DMPC. In a second step, a molecular dynamics (MD) simulation allowed for a more representative model of the bicelle bilayer while monitoring the amphiphiles and their interactions on the molecular level. In a final step, we moved away from the models and investigated the effect of temperature on the structure and magnetic alignment of Chol-NH2 doped bicelles by SANS. The DMPC/steroid monolayer studies showed that Chol-OH induces a larger condensation effect than Chol-NH2 at steroid contents of 16 and 20 mol %. However, this tendency was inversed at steroid contents of 10, 30, and 40 mol %. Although the MD simulation with 16 mol % steroid revealed that both compounds induce a liquid-ordered state in DMPC, the bilayer containing Chol-NH2 was much less ordered than the analogous system containing Chol-OH. Chol-NH2 underwent significantly more hydrogen bonding interactions with neighboring DMPC lipids than Chol-OH. It seems that, by altering the dynamics of the hydrophilic environment of the bicelle, Chol-NH2 changes the crystal field and angle of the phospholipid-lanthanide DMPE-DTPA/Tm3+ complex. These parameters largely determine the magnetic susceptibility Δχ of the complex, explaining the SANS results, which show significant differences in magnetic alignment of the steroid doped bicelles. Highly magnetically alignable DMPC/Chol-NH2/DMPE-DTPA/Tm3+ (molar ratio 16:4:5:5) bicelles were achieved up to temperatures of 35 °C before a thermoreversible rearrangement into nonalignable vesicles occurred. The results confirm the potential of Chol-NH2 doped bicelles to act as building blocks for the development of the magnetically responsive soft materials of tomorrow.

Mastering the magnetic susceptibility of magnetically responsive bicelles with 3ß-amino-5-cholestene and complexed lanthanide ions.

The magnetic susceptibility of lanthanide-chelating bicelles was selectively enhanced by introducing 3ß-amino-5-cholestene (aminocholesterol, Chol-NH2) in the bilayer. Unprecedented magnetic alignment of the bicelles was achieved without altering their size. An aminocholesterol conjugate (Chol-C2OC2-NH2), in combination with different lanthanide ions, offers the possibility of fine-tuning the bicelle's magnetic susceptibility.

Molecular engineering of lanthanide ion chelating phospholipids generating assemblies with a switched magnetic susceptibility.

Lanthanide ion (Ln3+) chelating amphiphiles are powerful molecules for tailoring the magnetic response of polymolecular assemblies. Mixtures of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA) complexed to Ln3+ deliver highly magnetically responsive bicelles. Their magnetic properties are readily tuned by changing the bicellar size or the magnetic susceptibility Δχ of the bilayer lipids. The former technique is intrinsically bound to the region of the phase diagram guarantying the formation of bicelles. Methods aiming towards manipulating the Δχ of the bilayer are comparatively more robust, flexible and lacking. Herein, we synthesized a new Ln3+ chelating phospholipid using glutamic acid as a backbone: DMPE-Glu-DTPA. The chelate polyhedron was specifically engineered to alter the Δχ, whilst remaining geometrically similar to DMPE-DTPA. Planar asymmetric assemblies hundreds of nanometers in size were achieved presenting unprecedented magnetic alignments. The DMPE-Glu-DTPA/Ln3+ complex switched the Δχ, achieving perpendicular alignment of assemblies containing Dy3+ and parallel alignment of those containing Tm3+. Moreover, samples with chelated Yb3+ were more alignable than the Tm3+ chelating counterparts. Such a possibility has never been demonstrated for planar Ln3+ chelating polymolecular assemblies. The physico-chemical properties of these novel assemblies were further studied by monitoring the alignment behavior at different temperatures and by including 16 mol% of cholesterol (Chol-OH) in the phospholipid bilayer. The DMPE-Glu-DTPA/Ln3+ complex and the resulting assemblies are promising candidates for applications in numerous fields including pharmaceutical technologies, structural characterization of membrane biomolecules by NMR spectroscopy, as contrasting agents for magnetic resonance imaging, and for the development of smart optical gels.

Tailoring Bicelle Morphology and Thermal Stability with Lanthanide-Chelating Cholesterol Conjugates.

Bicelles composed of DMPC and phospholipids capable of chelating lanthanide ions, such as 1,2-dimyristoyl-sn-glycero-3-phospho-ethanolamine-diethylene triaminepentaacetate (DMPE-DTPA), are highly tunable magnetically responsive soft materials. Further doping of these systems with cholesterol-DTPA conjugates complexed to a lanthanide ion considerably enhances the bicelle's size and magnetic alignability. The high value of these cholesterol conjugates for bicelle design remains largely unexplored. Herein, we examine how molecular structural alterations within the cholesterol-DTPA conjugates lead to contrasting self-assembled polymolecular aggregate structures when incorporated into DMPC/DMPE-DTPA/Tm(3+) bilayers. The nature of the linker connecting the DTPA-chelating moiety to the sterol backbone is examined by synthesizing conjugates of various linker lengths and polarities. The incorporation of these compounds within the bilayer results in polymolecular aggregate geometries of higher curvature. The increasing degrees of freedom for conformational changes conveyed to the chelator headgroup with increasing linker atomic length reduce the cholesterol-DTPA conjugate's critical packing parameter. Consequently, an inverse correlation between the number of carbon atoms in the linker and the bicelle radius is established. The introduction of polarity into the carbon chain of the linker did not cause major changes in the polymolecular aggregate architecture. Under specific conditions, the additives permit the formation of remarkably temperature-resistant bicelles. The versatility of design offered by these amphiphiles gives rise to new and viable tools for the growing field of magnetically responsive soft materials.

Quantification of Spontaneous W/O Emulsification and its Impact on the Swelling Kinetics of Multiple W/O/W Emulsions.

An osmotic imbalance between the two water phases of multiple water-in-oil-in-water (W1/O/W2) emulsions results in either emulsion swelling or shrinking due to water migration across the oil layer. Controlled mass transport is not only of importance for emulsion stability but also allows transient emulsion thickening or the controlled release of encapsulated substances, such as nutriments or simply salt. Our prior work has shown that mass transport follows two sequential stages. In the first stage, the oil-phase structure is changed in a way that allows rapid, osmotically driven water transport in the second, osmotically dominated stage. These structural changes in the oil layer are strongly facilitated by the spontaneous formation of tiny water droplets in the oil phase, induced by the oil-soluble surfactant, i.e., polyglycerol polyricinoleate (PGPR). This study provides a simple method based on microscopy image analysis, allowing a detailed investigation of spontaneous W/O emulsification. It quantitatively describes the volume of droplets generated and the rate of droplet creation. Moreover, it describes the effect of spontaneous W/O emulsification on the swelling kinetics of microfluidic processed W1/O/W2 emulsions. Two different concentration regimes of the oil-soluble surfactant are identified: below a critical concentration the overall water transport rate increases, and above a critical concentration water transport stagnates because of maximized structure formation.

Decoupling of mass transport mechanisms in the stagewise swelling of multiple emulsions.

This contribution reports on the mass transport kinetics of osmotically imbalanced water-in-oil-in-water (W1/O/W2) emulsions. Although frequently studied, the control of mass transport in W1/O/W2 emulsions is still challenging. We describe a microfluidics-based method to systematically investigate the impact of various parameters, such as osmotic pressure gradient, oil phase viscosity, and temperature, on the mass transport. Combined with optical microscopy analyses, we are able to identify and decouple the various mechanisms, which control the dynamic droplet size of osmotically imbalanced W1/O/W2 emulsions. So, swelling kinetics curves with a very high accuracy are generated, giving a basis for quantifying the kinetic aspects of transport. Two sequential swelling stages, i.e., a lag stage and an osmotically dominated stage, with different mass transport mechanisms are identified. The determination and interpretation of the different stages are the prerequisite to control and trigger the swelling process. We show evidence that both mass transport mechanisms can be decoupled from each other. Rapid osmotically driven mass transport only takes place in a second stage induced by structural changes of the oil phase in a lag stage, which allow an osmotic exchange between both water phases. Such structural changes are strongly facilitated by spontaneous water-in-oil emulsification. The duration of the lag stage is pressure-independent but significantly influenced by the oil phase viscosity and temperature.

Structural and mechanical anisotropy in plant-based meat analogues.

The rising demand for plant-based meat analogues as alternatives to animal products has sparked interest in understanding the complex interplay between their structural and mechanical properties. The ability to manipulate the processing parameters and protein blend composition offers fundamental insights into the texturization process and holds economic and sustainable implications for the food industry. Consequently, the correlation between mechanical and structural properties in meat analogues is crucial for achieving consumer satisfaction and successful market penetration, providing comprehensive insights into the textural properties of meat analogues and their potential to mimic traditional animal produce. Our study delves into the relationship between structural and mechanical anisotropy in meat analogues produced using high moisture extrusion cooking, which involves blending protein, water, and other ingredients, followed by a controlled heating and cooling process to achieve a fibrous texture akin to traditional meat. By employing techniques such as scanning small-angle X-ray scattering, scanning electron microscopy, and mechanical testing we investigate the fibrous structure and its impact on the final texture of meat analogues. We show that textural and structural anisotropy is reflected on the mechanical properties measured using tensile and dynamic mechanical techniques. It is demonstrated that the calculated anisotropy indexes, a measure for the degree of textural and structural anisotropy, increase with increasing protein content. Our findings have significant implications for the understanding and development of plant-based meat analogues with structures that can be tuned to closely resemble the animal meat textures of choice, thereby enabling consumers to transition to more sustainable dietary choices while preserving familiar eating habits.

Enzymatic degradation of pea fibers changes pea protein concentrate functionality.

Pea proteins are gaining increased interest from both the food industry as well as from consumers. Pea protein isolates (PPI) excel at forming meat-like textures upon heating while pea protein concentrates (PPC) are more challenging to transform into highly sought-after foods. PPCs are richer in dietary fibers (DF) and are more sustainable to produce than PPI. In this work, degradative enzymes were used to modify the functionality of PPC-water blends with a focus on texturization upon heating. Three enzyme solutions containing ß-glucanases, hemicellulases, pectinases, xylanase, and cellulases were added to 65 wt% PPC blends. The effect of these enzymatic pretreatments was measured by monitoring the torque in a mixing reactor during blending, differential scanning calorimetry (DSC), high-pressure shear rheology (HPSR), and DF content and size analysis. Four endothermic peaks were detected in the DSC thermograms of PPC, namely at 63 °C, 77 °C, 105 °C and 123 °C. The first three peaks were attributed to phase transition and gelation temperatures of the starches and proteins constituting PPC. No endothermic peaks were measured for PPI blends. Enzyme solutions containing ß-glucanases, hemicellulases, pectinases, and xylanases increased the endothermic energy of all peaks, hinting at an effect on the gelation properties of PPC. The same enzymes decreased the resistance to flow of PPC blends and induced a shift of the weight average molecular weight (Mw) distribution of soluble dietary fibers (SDF) towards smaller values while increasing the fraction of SDF by decreasing the insoluble dietary fiber (IDF) content. The solution containing cellulases did not change the DSC results or the viscosity of the PPC mixture, nor did it affect the IDF and SDF contents. On the other hand HPSR measurements of heated PPC samples up to 125 °C showed that all tested enzyme solutions decreased the complex viscosity of PPC-water blends to values similar to PPI-water blends. We demonstrated that degradative enzymes can enhance the functionality of less refined protein-rich ingredients based on pea and other vegetal sources. Using optimized enzyme blends for targeted applications can prove to be a key changer in the development and improvement of sustainable protein-rich foods.

Exploring the effects of structure and melting on sweetness in additively manufactured chocolate.

In view of the health concerns associated with high sugar intake, this study investigates methods to enhance sweetness perception in chocolate without increasing its sugar content. Using additive manufacturing, chocolate structures were created from masses with varying sugar and fat compositions, where hazelnut oil served as a partial cocoa butter replacement. The study found that while variations in sugar content minimally affected the physical properties of the chocolate masses, hazelnut oil significantly modified melting behavior and consumption time. Chocolate masses with higher hazelnut oil content but similar sugar content exhibited a 24% increase in sweetness perception, likely due to accelerated tastant (i.e., sucrose) release into saliva. Multiphase structures, designated as layered, cube-in-cube, and sandwich structures, exhibited less sensory differences compared to the homogeneous control. Nonetheless, structures with hazelnut oil-rich outer layers resulted in an 11% increase in sweetness perception, even without sugar gradients. This suggests that tastant release plays a more critical role than structural complexity in modifying sweetness perception. This research highlights the efficacy of simpler multiphase structures, such as sandwich designs, which offer sensory enhancements comparable to those of more complex designs but with reduced manufacturing effort, thus providing viable options for industrial-scale production.

Valorization of cocoa pod side streams improves nutritional and sustainability aspects of chocolate.

Chocolate production faces nutritional, environmental and socio-economic challenges present in the conventional cocoa value chain. Here we developed an approach that addresses these challenges by repurposing the often-discarded pectin-rich cocoa pod endocarp and converting it into a gel. This is done using cocoa pulp juice concentrate to replace traditional sugar from sugar beets. Although swelling of fibres, proteins and starches can limit gel incorporation, our proposed chocolate formulation contains up to 20 wt% gel. It also has comparable sweet taste as traditional chocolate while offering improved nutritional value with higher fibre and reduced saturated fatty acid content. A cradle-to-factory life cycle assessment shows that large-scale production of this chocolate could reduce land use and global warming potential compared with average European dark chocolate production. The process also provides opportunities for diversification of farmers' income and technology transfer, offering potential socio-economic benefits for cocoa-producing regions.

External surface area determination of lipid vesicles using trinitrobenzene sulfonate and ultraviolet/visible spectrophotometry.

The lamellarity of liposomes is an important parameter to be controlled in liposomal delivery-release applications. A practical estimate of the degree of liposome lamellarity can be obtained by measuring the relative external surface area of the liposomes using a chemical assay. All such assays are based on a signal change caused by exposed marker lipids on reaction with a specific externally added reagent. However, a quantitative determination is often distorted by background reactions and contributions of internal lipid labeling. In the so-called TNBS assay, the marker lipid is phosphatidylethanolamine (PE) and the externally added reagent is TNBS (2,4,6-trinotrobenzene sulfonate). Mechanistic aspects of the TNBS assay were considered for improving the assay. Internal lipid labeling via PE flip-flop and/or TNBS permeation was minimal not only in cholesterol-containing liposomes but also in cholesterol-free liposomes if in the latter case membrane fluidity was decreased by slightly increasing the PE content. Compared with earlier versions of the TNBS assay, the amount of marker lipid and the time for analysis could be reduced considerably. The elaborated protocol was also applied to liposomes prepared from lipidic egg yolk isolates, offering a simple and inexpensive method for the development and in-process control of new liposome formation technologies.

Alignment of bicelles studied with high-field magnetic birefringence and small-angle neutron scattering measurements.

Birefringence measurements at high magnetic field strength of up to 33 T were used to detect magnetically induced alignment of bicelles composed of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC), cholesterol, and 1,2-dimyristoyl-sn-glycero-3-phosphoethanolamine-diethylenetriaminepentaacetate (DMPE-DTPA) with complexed lanthanide ions. These birefringence measurements together with a small-angle neutron scattering (SANS) analysis in a magnetic field showed parallel alignment of the bicelles if the lanthanide was thulium (Tm(3+)), and perpendicular alignment with dysprosium (Dy(3+)). With the birefringence measurements, the order parameter S can be determined as a function of the magnetic field strength, if the magnetic alignment reaches saturation. Additional structural information can be obtained if the maximum induced birefringence is considered. The degree of alignment of the studied bicelles increased with decreasing temperature from 40 to 5 °C and showed a new bicellar structure comprising a transient hole formation at intermediate temperatures (20 °C) during heating from 5 to 40 °C.

Foams stabilized by multilamellar polyglycerol ester self-assemblies.

The importance of surfactant self-assemblies in foam stabilization is well-known. The aim of the current study was to investigate the self-assemblies of the nonionic surfactant polyglycerol ester (PGE) in bulk solutions, at the interface and within foams, using a combined approach of small-angle neutron scattering, neutron reflectivity, and electron microscopy. PGE bulk solutions contain vesicles as well as open lamellar structures. Upon heating of the solutions the lamellar spacing increases, with significant differences in the presence of NaCl or CaCl(2) as compared to the standard solution. The adsorption of the multilamellar structures present in the bulk solutions lead to a multilayered film at the air-water interface. The ordering within this film was increased as a result of a 20% area compression mimicking a coalescence event. Finally, PGE foams were shown to be stabilized not only by strong interfacial films but also by agglomerated self-assemblies within the interstitial areas of the foams.

Micro-foaming of plant protein based meat analogues for tailored textural properties.

Meat-like foods based on plant protein sources are supposed to be a solution for a more sustainable sustenance of the world population while also having a great potential to reduce the impact on climate change. However, the transition from animal-based products to more climate-friendly alternatives can only be accomplished when consumers' acceptance of plant-based alternatives is high. This article introduces a novel micro-foaming process for texturized High-Moisture Meat Analogues (HMMA) conferring enhanced structural properties and a new way to tailor the mechanical, appearance and textural characteristics of such products. First, the impact of nitrogen injection and subsequent foaming on processing pressures, temperatures and mechanical energy were assessed using soy protein concentrate and injecting nitrogen fractions in a controlled manner in the range of 0 wt% to 0.3 wt% into the hot protein melt. Direct relationships between related extrusion parameters and properties of extruded HMMAs were established. Furthermore, optimized processing parameters for stable manufacturing conditions were identified. Secondly, so produced HMMA foams were systematically analyzed using colourimetry, texture analysis, X-ray micro-tomography (XRT) and by performing water and Preprint submitted to Innovative Food Science and Emerging Technologies June 17, 2023 oil absorption tests. These measurements revealed that perceived lightness, textural hardness, cohesiveness and overrun can be tailored by adapting the injected N2 concentrations provided that the gas holding capacity of the protein matrix is high enough. Moreover, the liquid absorption properties of the foamed HMMA were greatly optimized. XRT measurements showed that the porosity at the center of the extrudate strands was the highest. The largest porosity of 53% was achieved with 0.2 wt% N2 injection, whilst 0.3 wt% N2 lead to destructuration of the HMMA foam structure through limited gas dispersion and wall slip layer formation. The latter can, nonetheless, be improved by adapting the processing parameters. All in all, this novel extrusion microfoaming process opens new possibilities to enhance the structural properties of plant-based HMMA and ultimately, consumers' acceptance.