This work reports on an in-depth characterization of the nano- and microstructure of extruded starch foams loaded with the microalga Spirulina (1, 5 and 10 wt%), as well as the implications of Spirulina incorporation on the textural properties of the foams. Due to the gelatinization process occurring during extrusion, the crystalline and lamellar structures originally present in the starch granule were disrupted, resulting in very amorphous foams. Moreover, the crystalline structure of the fatty acids present in the raw microalga was lost during processing. The presence of Spirulina intracellular components induced the formation of more thermally-stable V-type crystallites through complexation with amylose, hence producing slightly more crystalline foams (XC~5–9%) than the pure extruded starch (XC ~3%). This affected the microstructure of the hybrid foams, which showed more densely packed and well-connected porous structures. Microstructural changes had an impact on the texture of the foams, which became harder with greater Spirulina loadings. The foams underwent very limited re-crystallization upon storage, which was further reduced by the presence of Spirulina. Interestingly, the free fatty acids from Spirulina re-crystallized and the resistant starch content in the 10% Spirulina foam increased, which could potentially be interesting from a nutritional perspective. These results show the potential of extrusion cooking to produce healthier snack foods and highlight the suitability of advanced characterization tools such as neutron tomography and small angle X-ray scattering to investigate food structure. 

Plastics is a group of materials commonly encountered on a daily basis by many people. They have enabled rapid, low-cost manufacturing of products with complicated geometries and have contributed to the weight reduction of heavy components, especially when produced into a foamed structure. Despite the many advantages of plastics, some drawbacks such as the often fossil-based raw-material and the extensive littering of the material in nature, where it is not degraded for a very long time, needs to be dealt with. One way to address at least one of the issues could be to use polymers from nature instead of fossil-based ones. Here, a β-glucan concentrate originating from barley was investigated. The concentrate was processed into a foam by hot-melt extrusion, and the processing window was established. The effect of different blowing agents was also investigated. Water or a combination of water and sodium bicarbonate were used as blowing agents, the latter apparently giving a more uniform pore structure. The porous structure of the foamed materials was characterized mainly by using a combination of confocal laser scanning microscope and image analysis. The density of the samples was estimated and found to be in a similar range as some polyurethane foams. A set of 3D parameters were also quantified on two selected samples using X-ray microtomography in combination with image analysis, where it was indicated that the porous structure had a pre-determined direction, which followed the direction of the extrusion process. © 2019, The Author(s).

High-energy synchrotron radiation has been demonstrated to be a powerful tool for materials characterization. The development of novel methodologies is still ongoing, driven by major technological advances regarding the available source brilliance and efficient large area detectors. The Swedish Materials Science beamline at PETRA III is dedicated to materials characterization by high-energy X-rays and scheduled to enter into user operation starting August 2019. The beamline has been designed in particular for the combination of two complementary techniques: wide and small angle scattering and imaging. The beamline design is presented briefly and the different techniques are reviewed with regard to the contrast mechanisms and the ability to obtain spatially resolved information.

Photonic materials for high-temperature applications need to withstand temperatures usually higher than 1000 °C, whilst keeping their function. When exposed to high temperatures, such nanostructured materials are prone to detrimental morphological changes, however the structure evolution pathway of photonic materials and its correlation with the loss of material's function is not yet fully understood. Here we use high-resolution ptychographic X-ray computed tomography (PXCT) and scanning electron microscopy (SEM) to investigate the structural changes in mullite inverse opal photonic crystals produced by a very-low-temperature (95 °C) atomic layer deposition (ALD) super-cycle process. The 3D structural changes caused by the high-temperature exposure were quantified and associated with the distinct structural features of the ceramic photonic crystals. Other than observed in photonic crystals produced via powder colloidal suspensions or sol-gel infiltration, at high temperatures of 1400 °C we detected a mass transport direction from the nano pores to the shells. We relate these different structure evolution pathways to the presence of hollow vertexes in our ALD-based inverse opal photonic crystals. Although the periodically ordered structure is distorted after sintering, the mullite inverse opal photonic crystal presents a photonic stopgap even after heat treatment at 1400 °C for 100 h.