Etude de l'eau par RMN et IRM dans les procédés laitiers

International audienceL'eau, constituant majeur de nombreux produits alimentaires, a une influence déterminante sur les procédés de transformations, les caractéristiques et la stabilité des produits alimentaires. Les techniques RMN et d'imagerie RMN (IRM) qui fournissent des informations sur la teneur et l'état dynamique de l'eau dans les milieux complexes sont particulièrement adaptées pour caractériser les interactions entre le produit et les variables des procédés. L'objectif de ce document est de présenter quelques exemples de travaux de RMN et d'IRM réalisés dans le secteur des produits laitiers

Defects segmentation on 'Golden Delicious' apples by using colour machine vision

A method based on colour information is proposed to detect defects on 'Golden Delicious' apples. In a first step, a colour model based on the variability of the normal colour is described. To segment the defects, each pixel of ail apple image is compared with the model. If it matches the pixel, it is considered as belonging to healthy tissue, otherwise as a defect. Two other steps refine the segmentation, using either parameters computed on the whole fruit, or values computed locally. Some results are shown and discussed. The algorithm is able to segment a wide range of defects. (C) 1998 Elsevier Science B.V. All rights reserved

Quantitative study of the signal decay due to magnetic susceptibility interfaces: MRI simulations and experiments

In MRI, characterization of magnetic susceptibility artifacts can be necessary in a wide range of studies. We used both experience on a 0.2T magnet and MRI simulations to assess the signal decay over echo time at different pixel sizes in the case of air-water interfaces. The particular experimental signal modulation, reproduced in simulation, was clarified. Concordance between simulation and experience will enable further studies of magnetic susceptibility effects with more complex objects like in molecular imaging or in porous media imaging

Signal decay due to susceptibility-induced intravoxel dephasing on multiple air-filled cylinders: MRI simulations and experiments

[Departement_IRSTEA]EA [TR1_IRSTEA]TEPSA / IRMFOODInternational audienceObjective Characterization of magnetic susceptibility artefacts with assessment of the gradient-echo signal decay function of echo time, pixel size, and object geometry in the case of air-filled cylinders embedded in water. Materials and methods Experiments were performed with a 0.2T magnet on a network of small interacting air-filled cylinders along with Magnetic resonance imaging (MRI) simulations integrating intravoxel dephasing. Signal decay over echo time was assessed at different pixel sizes on real and simulated images. The effects of radius, distance between cylinders and main magnetic field were studied using simulation. Results Signal loss was greater as echo time or pixel size increased. Voxel signal decay was not exponential but was weighted by sinus cardinalis functions integrating echo time, pixel size and field inhomogeneities which depended on main magnetic field strength and geometric configuration of the object. Simulation was able to model signal decay, even for a complex object constituted of several cylinders. The specific experimental signal modulation we observed was thus reproduced and explained by simulation. Conclusion The quantitative signal decay approach at 0.2T can be used in characterization studies in the case of locally regular air/water interfaces as the signal depends on object size relative to pixel size and is relevant to the geometric configuration. Moreover, the good concordance between simulation and experiments should lead to further studies of magnetic susceptibility effects with other objects such as networks of spheres. MRI simulation is thus a potential tool for molecular and porous media imaging

Etude de l'eau par RMN et IRM dans les procédés laitiers

L'eau, constituant majeur de nombreux produits alimentaires, a une influence déterminante sur les procédés de transformations, les caractéristiques et la stabilité des produits alimentaires. Les techniques RMN et d'imagerie RMN (IRM) qui fournissent des informations sur la teneur et l'état dynamique de l'eau dans les milieux complexes sont particulièrement adaptées pour caractériser les interactions entre le produit et les variables des procédés. L'objectif de ce document est de présenter quelques exemples de travaux de RMN et d'IRM réalisés dans le secteur des produits laitiers

Characterization of signal loss due to magnetic susceptibility interfaces in gradient-echo imaging by simulation and experiments

Magnetic susceptibility interfaces result in signal loss in gradient-echo MR images. The characterization of these susceptibility artefacts can be of greater importance in number of studies such as paramagnetic markers tracking, BOLD imaging or porous media analyses. We are interested in the signal decay at different pixel sizes in the case of an air-water interface in 2D GE imaging. We used both experience on a 0.2T magnet and MRI simulation to assess the signals behaviours

Rehydration of casein powders: effects of added mineral salts and salt addition methods on water transfer

Enrichment of milk with micellar casein decreases water transfer during the rehydration of milk powders. In this study, the effects of the ion environment and the ion addition method on the rehydration kinetics were found to be dependent on the changes in the micellar casein. For example, adding citrate or phosphate solution to the micellar casein suspension before drying considerably increased rehydration rates and this was related to the destruction of the micelle structure. Water transfer in the casein suspension was improved by adding NaCl during rehydration: this effect may be explained by the more hygroscopic nature of NaCl rather than by extensive modification of the micellar structure. The addition of CaCl2 considerably affected micelle organization and led to the formation of insoluble structures during spray drying

Etude d'un systeme de tri aux defauts d'aspects des fruits

SIGLECNRS AR 11174 / INIST-CNRS - Institut de l'Information Scientifique et TechniqueFRFranc