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Background Until recently, the main/unique mechanism used to describe porosity was the evolution of the empty spaces formed as a result of water removed during drying. Although we have suggested, previously, two functions (shrinkage and collapse) to capture both the empty spaces formed as a result of water removed (first mechanism), and the evolutions initial empty spaces (second mechanism), it is still not clear yet how to interpret separately the two mechanisms. Indeed, so far, there is no technical measurement available to isolate these two mechanisms form each other. Scope and approach In this investigation, we aim at confirming the effect of the second mechanism (evolution of initial porosity) that should be considered when modelling porosity of foodstuffs. A selection of fresh products (eggplant, zucchini and mushroom) were chosen as prototypes for which the initial porosity cannot be ignored. A deep analysis of some published data, for apple and pear, was performed aiming at understanding the sequence of these two mechanisms during the drying processes. Key findings and conclusions By using X-ray microtomography (μ-CT) imaging, it has been possible to demonstrate that the initial empty spaces “initial porosity” of some fresh products is highly significant. The results of some mathematical simulations revealed that the two mechanisms are interrelated and therefore cannot be fully isolated and interpreted separately. This study opens a challenging scientific debate and an opportunity for finding a new approach for measuring/monitoring separately the two mechanisms during drying processes. |
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