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Berlin, Germany

Seim C.,Max Born Institute for Nonlinear Optics and Short Pulse Spectroscopy | Seim C.,TU Berlin | Seim C.,Berlin Laboratory for Innovative X ray Technologies | Reineke K.,Leibniz Institute for Agricultural Engineering | And 10 more authors.
Innovative Food Science and Emerging Technologies | Year: 2015

Measurements were carried out on high pressure treated (HPT) bacterial endospores of the Bacillus subtilis strain PS832 by means of laboratory (LTXM) and synchrotron based transmission soft X-ray microscopy (SynchTXM). Using LTXM at 500 eV HPT spores could be identified by a higher transparency, due to dipicolinic acid (DPA) release from the spore's core, and their shriveled appearance caused by air-drying. Dormant spores were investigated at different photon energies at SynchTXM. Inner structures were visualized and it was shown that at a photon energy of 280 eV the micrographs yielded bigger absorption differences, and thus better contrast between the core/coat and the peptidoglycan-rich cortex. Tilt series of dormant and HPT spores were reconstructed. Virtual sections revealed the dormant spores' core, cortex and coat without the need to physically slice the sample. It was also possible to visualize the inside of the HPT spores, which proved to be void of DPA. Industrial relevance Isostatic high pressure processing (HPP) is often regarded as the major recent technological innovation in food preservation. However, this technology is only applied in large scale for pasteurization and not for sterilization, which is largely due to the unknown inactivation mechanisms of highly resistant bacterial endospores. The structural analysis of high pressure treated endospores by X-ray microscopy could be used to study the progress of spore germination and inactivation under pressure and may add to the information already gathered in previous studies such as (Reineke et al., 2013) to establish the high pressure thermal sterilization at industrial scale. This technology in combination with different extrinsic factors like chemical or thermal preservation may open up new possibilities for a multi-target spore inactivation strategy for food sterilization. © 2015 Elsevier Ltd.

Gerlach M.,Physikalisch - Technische Bundesanstalt | Anklamm L.,TU Berlin | Antonov A.,Optigraph GmbH | Grigorieva I.,Optigraph GmbH | And 6 more authors.
Journal of Applied Crystallography | Year: 2015

Highly annealed pyrolytic graphite (HAPG) is an advanced type of pyrolytic graphite that, as a mosaic crystal, combines high integral reflectivity with a very low mosaicity of typically less than 0.1°. When used as dispersive X-ray optics, a high resolving power has been observed, rendering HAPG very suitable for applications in high-resolution X-ray spectroscopy, which conventionally relies on ideal crystals. For the design and modelling of HAPG crystals in applications requiring high spectral resolution, the diffraction properties must be known very accurately. To close this gap, a comprehensive characterization of HAPG crystals was performed that allows for modelling of the diffraction properties in different diffraction orders over a broad spectral range. The crystal properties under investigation are the mosaic spread, the peak reflectivity and the intrinsic reflection width. The investigations were carried out for different thickness crystal films, which were mounted adhesively on a substrate. It is shown that the diffraction properties are strongly correlated to the grade of adhesion, which depends crucially on the substrate material and its surface properties. The investigations were performed using monochromated tunable synchrotron radiation of high spectral purity with a high-precision experimental setup and calibrated detection devices at the electron storage ring BESSY II. © 2015 International Union of Crystallography.

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