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Artigues-près-Bordeaux, France

Herremans E.,Catholic University of Leuven | Bongaers E.,Bruker | Estrade P.,VSG | Gondek E.,Warsaw University of Life Sciences | And 11 more authors.
Innovative Food Science and Emerging Technologies | Year: 2013

Proper control of the texture properties of aerated foods demands accurate measurement tools. Aerated sugar gels with identical composition but different microstructures were produced by applying different mixing times of 2, 4 and 8 min. Compression test and acoustic emission measurements were carried out to characterize the mechanical properties of these foams. Significant differences in deformation properties and number of acoustic events were found depending on the foaming time, indicating differences in texture. Microstructural attributes such as bubble size and bubble number distributions of the different foams were measured based on micro- and nano-CT and were found to differ between the foams. Additionally, time and spatially resolved diffuse spectroscopy were used to evaluate their optical properties. While, as expected for foams with the same chemical composition, the absorption properties were not significantly different, a relationship between scattering and microstructural properties was found. The results show that microstructural properties affect the texture of aerated foams. Moreover, the latter can be measured nondestructively using time and spatially resolved diffuse spectroscopy. Industrial relevance Food aeration is one of the fastest growing unit operations in the food industry (Zúñiga & Aguilera, 2008, 2009). Proper design and control of the texture properties of aerated foods demand accurate measurement tools of microstructural features. Food microstructure is defined as the spatial arrangement of structural components of food and their interactions. Structural elements include water and oil droplets, gas cells, fat crystals, strands, granules, micelles and interfaces. Changes in the microstructure during storage and processing can be significant and affect the macroscopic appearance, quality and perception of food. Due to the microscopic complexity, straightforward methodologies that link quality to food microstructure do not exist today, as opposed to many engineering materials with a well ordered microstructure, for which the relationship with macroscopic properties can be easily understood based on fundamental physics. The only way forward is to develop methods that measure directly the microstructural properties of foods. © 2013 Elsevier Ltd. All rights reserved.

Herremans E.,Catholic University of Leuven | Verboven P.,Catholic University of Leuven | Nicolai B.M.,Catholic University of Leuven | Wevers M.,Catholic University of Leuven | And 3 more authors.
Acta Horticulturae | Year: 2015

Preservation of quality of apples is a premium target during storage of these fresh products. However, during the production and storage the fruit can develop undesired quality losses, also during CA (controlled atmosphere) storage. 'Braeburn' browning disorder (BBD) is such a CA related internal disorder, that cannot be distinguished on the fruit exterior. However, internal disorders are likely to reflect massive changes in the microstructure of the fruit tissue. There is a need for a non-destructive evaluation of internal fruit quality that is fast, reliable and can be used for on-line sorting of disordered fruits. X-rays can detect local density changes and are therefore investigated as a promising tool to detect brown and hollow tissues in apples. A first objective in this study was to investigate microstructural changes during development of internal flesh browning of 'Braeburn' apples. Therefore apple samples were scanned using high resolution X-ray micro computed tomography, at regular intervals after harvest while storing under extreme CA conditions (1% O2, 5% CO2). We gained insight in the microstructure by applying image processing tools to virtually isolate single cells and pores, hereby enabling the detailed 3D characterisation of the in vivo microstructure in terms of the tissue connectivity, the internal air network and the distribution of pores inside the apple tissue in healthy and disordered fruits. Secondly, we wanted to investigate the feasibility of X-ray tomography to effectively detect these internal disorders at commercial speeds. We scanned a large number of fruits and performed image processing to detect the disorders. In the first trials we could detect affected fruits with a success ratio of 95%, although total scans times were rather high (10 min per fruit) . By significantly lowering the image acquisition time to 38 s, the sorting success was reduced to 82%. Further efforts are needed to speed up the measurements and test the image processing algorithms with newly scanned fruits, however, on-line measurements in a medical CT system have proven the potential applicability of X-ray CT in postharvest sorting facilities.

Herremans E.,Catholic University of Leuven | Verboven P.,Catholic University of Leuven | Bongaers E.,Bruker | Estrade P.,VSG | And 5 more authors.
Postharvest Biology and Technology | Year: 2013

Unfavourable gas conditions during controlled atmosphere storage may cause browning symptoms in 'Braeburn' apple fruit ('Braeburn' browning disorder or BBD). These symptoms are likely to reflect massive changes in the microstructure of the fruit tissue. In this study, individual cells, the internal air network and the 3-D distribution of pores inside 'Braeburn' apple tissue were examined using high resolution X-ray micro computed tomography. Different stages of BBD could be clearly resolved on the virtual cross-sections, granting a unique 3-D insight in tissue flooding and formation of cavities in 'Braeburn' tissue during the development of the disorder. Image analysis methods were applied to extract morphometric parameters such as porosity, anisotropy and connectivity to characterise microstructure. The discriminative power of these descriptors was proven by their ability to classify fruit tissue as healthy and disordered with a success rate of 97%. The observed distinct radial patterns of porosity, anisotropy and connectivity may help in explaining why 'Braeburn' is susceptible to BBD. © 2012 Elsevier B.V.

Gondek E.,Warsaw University of Life Sciences | Jakubczyk E.,Warsaw University of Life Sciences | Herremans E.,Catholic University of Leuven | Verlinden B.,42 Technology | And 7 more authors.
Journal of Cereal Science | Year: 2013

The aim of this work was to describe the texture and structure of crisp bread obtained with different extrusion parameters. The texture of different crisp bread samples was evaluated using a combination of acoustic and mechanical tests. The advantage of this measurement setup is the feasibility of simultaneous registering of the force-deformation characteristics, sounds (using an acoustic envelope detector coupled to the texture analyser with a microphone) as well as mechanical vibrations (registered using a piezoelectric sensor) generated during a penetration test. All analysed samples of bread were products with a crisp texture that emitted audible sounds with a significant intensity that could be registered with a microphone as well as with a contact method. Micro-CT cross-section images showed the highly porous structure of the crisp breads but variant 3 appeared to have thicker walls and larger cells than the other breads. © 2013 Elsevier Ltd.

Andra H.,Fraunhofer Institute for Industrial Mathematics | Combaret N.,VSG | Dvorkin J.,Stanford University | Glatt E.,Fraunhofer Institute for Industrial Mathematics | And 14 more authors.
Computers and Geosciences | Year: 2013

The key paradigm of digital rock physics (DRP) "image and compute" implies imaging and digitizing the pore space and mineral matrix of natural rock and then numerically simulating various physical processes in this digital object to obtain such macroscopic rock properties as permeability, electrical conductivity, and elastic moduli. The steps of this process include image acquisition, image processing (noise reduction, smoothing, and segmentation); setting up the numerical experiment (object size and resolution as well as the boundary conditions); and numerically solving the field equations. Finally, we need to interpret the solution thus obtained in terms of the desired macroscopic properties. For each of these DRP steps, there is more than one method and implementation. Our goal is to explore and record the variability of the computed effective properties as a function of using different tools and workflows. Such benchmarking is the topic of the two present companion papers. Here, in the first part, we introduce four 3D microstructures, a segmented Fontainebleau sandstone sample (porosity 0.147), a gray-scale Berea sample; a gray-scale Grosmont carbonate sample; and a numerically constructed pack of solid spheres (porosity 0.343). Segmentation of the gray-scale images by three independent teams reveals the uncertainty of this process: the segmented porosity range is between 0.184 and 0.209 for Berea and between 0.195 and 0.271 for the carbonate. The implications of the uncertainty associated with image segmentation are explored in a second paper. © 2012 Elsevier Ltd.

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