The chemical changes sustained by lignocellulosic biomass during hydrothermal treatment are reflected at multiple scales. This study proposes to benefit from this multiscale nature in order to provide a global understanding of biomass alterations during hydrothermal treatment. For this purpose, complementary imaging techniques—confocal Raman microscopy and X-ray nano-tomography—analysed by image processing and coupled to chemical measurements were used. This unique combination of analyses provided valuable information on topochemical and morphological changes of poplar samples, without the artefacts of sample preparation. At the cell wall level, holocellulose hydrolysis and lignin modifications were observed, which corresponded to anatomical modifications observed at higher scales. Overall, after treatment, samples shrank and had thinner cell walls. When subjected to more severe pre-treatments, cells were disrupted and detached from adjacent cells. Anatomical changes were then used to obtain quantitative indicators of the treatment severity. The effects of treatment at different scales can thus be quantitatively connected in both directions, from micro to macro and from macro to micro.
This paper presents an experimental device specially designed for the continuous measurement of mass and dimensions of samples submitted to convective drying. This experimental device consists of a magnetic suspension balance and an image acquisition system. The sample deformation is determined by image correlation using a custom software. The entire system is able to achieve accurate mass and dimension measurements over a wide range of temperature and relative humidity. In order to present the potential of this equipment, experimental data of highly deformable food products (potato and apple) submitted to several drying conditions are presented. The obtained results confirm that it is required to consider the actual sample surface to 2 determine the mass flux. This allowed a first drying stage to be observed for potato.Clear differences in physical behavior of these two vegetable products were also observed, for example, an isotropic shrinkage behavior for potato and an anisotropic behavior for apple. These results were explained by the anatomical structure of the products.
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