Soy protein isolates (SPIs) and concentrates (SPCs), which primarily consist of glycinin (11S globulin) and β[jls-end-space/]-conglycinin (7S globulin), are the dominant ingredients in the production of plant-based meat products using high-moisture extrusion (HME). Yet the links between their gelation and structure formation under HME are not fully understood. In this work, we employ small-angle scattering (SAS) techniques, complemented by rheology, on heat-set gels to elucidate the multiscale aggregation pathways of fractionated 11S and 7S globulins, and relate these to the extrudate structure. Heat-set gels revealed a three-level structural hierarchy: compact protein units that persist after heating; aggregates whose mid-scale size and morphology vary with pH; and networks characterised by clustering strength. Near the isoelectric point (pI), both globulin-enriched fractions formed particulate gels. Under these conditions, 7S globulin-enriched gels were stiffer because their smaller aggregates created a higher density of contacts per unit volume, resulting in a higher clustering strength. Away from the pI, fibrillar aggregation dominated, and 11S globulin-enriched gels became stiffer as a result of forming thicker and more tightly connected strands. At pH 7, blending experiments revealed that even small additions of 7S globulin weaken the gels; however, under HME, the same additions enhance anisotropy. Specifically, 7S globulin promotes deformability and alignment, while 11S globulin contributes to network strengthening through covalent crosslinks. Together, these results establish parallels between heat-induced gelation and extrusion, highlighting the complementary roles of 11S and 7S globulins in structuring high-moisture extrudates of soy proteins.

The development of novel plant-based meat alternatives that closely mimic the anisotropic structure of animal meat offers a solution to mitigate the adverse effects of animal meat consumption. The currently most widely adopted production route is shear processing through high-moisture extrusion (HME). The complex structure formation mechanisms that determine the final fibrous texture of extrudates have yet to be fully understood. The main obstacle is the lack of multiscale studies investigating the principles governing structure formation from the nano- to the macro-structural level. This work aims to address this knowledge gap by studying materials, collected after a dead-stop operation of an industrial pilot-plant scale extruder, with multiple characterisation techniques, such as Magnetic Resonance Imaging (MRI) and Small-Angle Scattering (SAS). We demonstrate that the nm- to μm-scale structure is formed already within the extruder barrels, and that sub-mm-scale anisotropy develops within the cooling die. Furthermore, we show that diffuse light reflectance (DR) probes the size and coarseness of the lamellar phase-separated regions.

Hypothesis: Pea proteins can act not only as interfacial stabilizers of oil-in-water emulsions but also as gelling agents in the continuous phase. Protein gelation, rather than droplet jamming, may be the main mechanism of emulsion stability, providing a physical explanation for the creaminess of high-protein plant-based emulsions. Experimental: Spin-echo small angle neutron scattering (SESANS) with D₂O/H₂O contrast variation was used to study 15% pea protein dispersions and emulsions with 40–60% rapeseed oil, 7.5% protein at pH 3 to 6.5. SESANS investigates length scales up to tens of micrometres, enabling simultaneous analysis of protein networks and oil droplets without dilution. Complementary small angle X-ray/neutron scattering were used to validate protein aggregate size, and hydration. Findings: Protein dispersions at neutral pH formed mass fractal networks with small individual building blocks (radius ∼38 Å, hydration ∼70%). Emulsions consisted of oil droplets embedded in these networks, with droplet radii decreasing at higher oil fractions due to an effective higher protein concentration in the continuous phase, creating a denser network. Dispersions and emulsions at lower pH contained aggregated clusters of denatured proteins. These coarse and inhomogeneous networks gave increasing droplet radii at lower pH. Contrast variation enabled the separation of protein and oil droplet scattering, demonstrating that protein gelation rather than droplet jamming is the main mechanism of stability. This gives a physical explanation of the high viscosity of high-protein plant-based emulsions and is promising for these plant materials to be used as gelling agents in food applications.

High-moisture extrusion (HME) is a proven industrial food processing technique used to create textured plant-protein materials that can serve as alternatives for animal meat. The required multiscale anisotropic structure of the extrudate can be achieved by selecting suitable HME process conditions, as well as by pH-shifting. In this work, we explored pH-shifting via the water feed, which is an attractive industrially-scalable approach. Soy protein concentrate (SPC) was extruded on lab-scale and extrudates were characterized ex situ, from molecular to mm scale, using Diffuse Reflectance (DR), Magnetic Resonance Imaging (MRI), Small-Angle-Scattering of Neutrons (SANS) or X-rays (SAXS). pH-shifting had a non-monotonic effect on extrudate hardness and anisotropic structure at both sub-mm (MRI) and μm (DR) scale. At the sub-μm scale, SANS and SAXS data indicated that, at pH > pI, the radius of protein nano-aggregates monotonically increases, accompanied by a transition from particulate to fibrillar protein aggregation. When pH was further shifted to alkaline conditions, the decrease in clustering strength and nematic order parameter pointed to an increase in intra- and inter-fibrillar repulsion, respectively. Protein extractability experiments indicated that the effects of pH-shifting on anisotropic structure formation could not be attributed to covalent intermolecular crosslinking. Thus, repulsive non-covalent electrostatic protein-protein interactions play a dominant role in the formation of multiscale anisotropic structure during SPC extrusion. The formation of an optimal anisotropic SPC extrudate structure is determined by the pH-dependent balance between fibrillar nano-aggregate clustering and electrostatic repulsion. Alkalization or acidification via the water feed implies that protein charge and structure may not be in equilibrium yet with the imposed pH conditions. The transient nature of pH-shifting via the water feed results in an intricate interplay with extrusion conditions. Therefore, control of anisotropic structure formation, via the water feed, in SPC extrudates, is extruder specific.

Capillary suspensions are unique materials, in which the rheological properties can be tuned by controlling the particle network through capillary interactions. To gain insights into the influence of particle properties on the network formation and accompanying gel strength for water-absorbing, biopolymeric particles, protein particles of two different sizes and water absorption capacities (WACs) were prepared. Utilizing SESANS, we describe a novel approach towards detecting changes in water distribution between and within particles. While effects of WAC seemed to be overpowered by concurrent variations in surface roughness, a larger particle size or lower roughness led to a lower initial gel strength and a subsequent much larger relative increase in gel strength upon water addition. Even though similar maximum gel strengths were obtained, indicating that particle properties had a comparably small influence once capillary forces dominated the systems, particle size played a critical role for network collapse with increasing particle clustering at larger water volumes. The results pinpoint subsequent knowledge gaps in the existing literature and demonstrate the tunability of biopolymer-based capillary suspensions over a wide gel strength range by adjustment of particle properties. These insights offer exciting opportunities for application of capillary-force controlled systems in the food, pharmaceutical and cosmetic industries.

The spin-echo small-angle neutron scattering (SESANS) technique utilises a series of inclined magnetic fields before and after the sample to encode the scattering angle into the polarisation to obtain a much higher resolution than in conventional SANS. The analogous technique (spin echo modulated SANS (SEMSANS)) implements spin manipulations before the sample only to encode the scattering into an intensity modulation. The technique can be combined with SANS to expand the length scale range probed from 1 nm to microns. Using McStas we show that using a series of four magnetic Wollaston prisms in two orthogonal pairs with a 90° rotation can be utilised to create SEMSANS modulations in 2-D. These modulations can also be of different periods in each encoding direction. This method can be applied to anisotropic scattering samples. Also this allows for the simultaneous measurement at two orthogonal independent spin-echo lengths. This technique yields directly information about the structure of oriented structures.

A round-robin study has been carried out to estimate the impact of the human element in small-angle scattering data analysis. Four corrected datasets were provided to participants ready for analysis. All datasets were measured on samples containing spherical scatterers, with two datasets in dilute dispersions and two from powders. Most of the 46 participants correctly identified the number of populations in the dilute dispersions, with half of the population mean entries within 1.5% and half of the population width entries within 40%. Due to the added complexity of the structure factor, far fewer people submitted answers on the powder datasets. For those that did, half of the entries for the means and widths were within 44 and 86%, respectively. This round-robin experiment highlights several causes for the discrepancies, for which solutions are proposed.

By introducing hydrophilic polymers into silicone medical devices, highly beneficial biomedical properties can be realized. An established solution to introduce hydrophilic polymers is to form an interpenetrating polymer network (IPN) by performing the hydrogel synthesis in the presence of silicone swollen in supercritical carbon dioxide. The precise distribution of the two polymers is not known, and determining this is the goal of this study. Neutron scattering and microscopy were used to determine the distribution of the hydrophilic guest polymer. Atomic force microscopy revealed that the important length scale on the surface of these materials is 10–100 nm, and spin-echo small-angle neutron scattering (SESANS) on IPNs submerged in D₂O revealed structures of the same scale within the interior and enabled quantification of their size. SESANS with hydration by D₂O proved to be the only scattering technique that could determine the structure of the bulk of these types of materials, and it should be used as an important tool for characterizing polymer medical devices.

Functionalized biomass waste sources of cellulose have drawn attention due to their high availability and sustainability properties. In this work we characterize the structural and flow properties of high-pressure homogenized citrus fiber cellulose dispersions, employing SAXS, rheology and rheo-MRI techniques. The high-pressure treatment disrupts the microfibrillar network within the citrus fibers, but leaves the individual microfibrils intact. Under moderate shear (0.1-100 s^-1) in a confined (<1 mm) geometry, these functionalized citrus fiber cellulose dispersions exhibit thixotropic shear-banding behavior accompanied by cooperative flow of microfibril flocs with correlation lengths ξ ~ 100 μm. The presented findings form a basis towards understanding and manipulating the structural and rheological properties of non-wood biomass cellulose microfibrils under industrially-relevant conditions.

Spray-drying is a widely used industrial technique and has shown an immense potential in the fields of nanoscience and technology. This is due to its ability to synthesize microgranules consisting of correlated nanostructures using evaporation induced assembly through bottom-up approach. Although the nature of correlation among the constituent nanoparticles and their size distribution could earlier be obtained by conventional Small-angle Scattering (SAS) technique, a statistically averaged quantitative measure of the shell thickness and hollowness of the formed granules remained a challenge. In this work, we have used Spin-echo Small-angle Neutron Scattering (SESANS) technique to characterize spray-dried nanostructured microgranules having different hollowness. It is shown that this non-destructive technique provided precise quantification of the granular sizes and hollowness by utilizing polarization property of neutrons in real space directly.

Small angle scattering is frequently applied to study the anisotropy in complex soft matter systems. One emerging application is to probe the multi-scale structure in food matrices; while few models are available to describe the anisotropic scattering pattern in a quantitative, yet simple manner. For this purpose, anisotropy is introduced to the Guinier–Porod model to study the scattering from non-spherical objects with a preferred orientation. This generalised anisotropic Guinier–Porod model can be adapted to approximate the sector scattering from both cylinders and ellipsoids (both prolate and oblate). In practice, it is applied to describe the anisotropic scattering from fibres in a meat analogue made of calcium caseinate. A good agreement is found between fitted dimensions of the fibres and those observed from the microscopy image. The effect of orientation distribution on the shape and intensity of the scattering pattern is further discussed and three means to obtain the orientation distribution of the symmetry axis are proposed. Given the model is straightforward and the fitting remains phenomenological, it provides a novel approach to extract information from complex food systems.