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The effects of the number of fat layers (4-162 layers) on expansion and loss of CO2 and water in Danish pastries (yeasted puff pastry) were studied at each processing step. Proving contributed to most of the expansion (200-300%) and no specific role of fat layers was evidenced at this stage; this was confirmed by measurements of CO2 released. Relative expansion during baking ranged from 20% to 65% for 4 to 32 fat layers and remained unchanged above 48 layers. Images cross sections of Danish pastry showed that bubbles were few for 4 fat layers, but very large (3-4 cm) and elongated in the direction of layering. For high numbers of fat layers, bubbles were numerous, smaller and round (2-7 mm). The loss of water vapor retention during baking in relation to fragmentation of fat layers during sheeting explained the leveling-off of expansion and the decreasing size of bubbles. © 2015 Published by Elsevier Ltd.

[Departement_IRSTEA]Ecotechnologies [TR1_IRSTEA]SPEE; International audience; The potentiality of MRI to quantify fat content in flesh and subcutaneous fat in fish cutlets was investigated. Low measurement time was aimed at in a view to handling large number of samples needed in selective breeding programs for example. Results on fresh and frozen-thawed cutlets were compared to assess this way of conservation. As MRI generates unwanted spatial variations of the signal, a correction method was developed enabling the measurement on several cutlets simultaneously in less than 3 min per sample. For subcutaneous fat, the results were compared with vision measurements. High correlations between both techniques were found (R2 = 0.77 and 0.87 for the ventral and dorsal part). Fat in flesh was validated vs NMR measurements. No statistical difference was found between fresh and frozen-thawed cutlets. RMSE was respectively 0.8% and 0.89%. These results confirmed the potentiality of MRI for fat measurement in fish particularly for a large number of samples.

International audience; Previous studies comparing Crassostrea gigas selected lines with different susceptibility to summer mortality concluded that the higher the reproductive effort the lower the survival. But they were acking individual follow up of this reproductive effort which would be of great interest to help us to understand the physiology of the oysters facing summer mortalities. The most frequently used method for assessing the volume of the gonad is to measure the area it occupies on histological sections. Gonad measurement by magnetic resonance imaging, in contrast, is non-destructive and therefore makes it possible to assess individual evolution as well as to compare individuals. The present study compared the values of gonad volume by this method with the values of gonad surface obtained by the histological method. The two methods were used successively to assess the volume of the gonads of the same individual oysters at different maturation stages. There is a very highly significant linear relation between the results of these two methods. The estimated uncertainty about the volume value is 29%. Causes of this uncertainty are considered and discussed.

International audience; Pulsed field gradient - nuclear magnetic resonance (PFG-NMR) was used to monitor the diffusion of caseins throughout the rennet coagulation of a highly concentrated casein suspension. Two types of casein species were distinguished according to their diffusing properties and attributed to the dissolved casein fraction, i.e. dissociated caseins and caseinomacropeptides (CMP), and casein particles, respectively. The NMR signal intensity coming from the dissolved casein fraction, which is related to the number of protons it contains, increased all along the experiment whereas the opposite tendency was observed for casein particles. This was explained by the increasing amount of CMP in the whey and the reciprocal loss of protons contained by casein particles, and used to quantitatively estimate the kinetics of the chymosin action. The diffusion of the dissolved casein fraction remained nearly constant during the coagulation process whereas, as revealed by rheometry measurements, the diffusion of casein particles was very sensitive to the structural reorganization of the sample. It decreased by about 35 % during the sol-gel transition and increased in similar proportions during the succeeding rise in gel porosity. Our results also provide different types of information on the respective behaviors of dissociated caseins and casein particles during the course of the process, the most remarkable one being that all the casein particles did not aggregate during the sol-gel transition of our sample. This strongly suggests that the rennet gelation of a concentrated dairy solution may be better visualized by the formation of a network backbone during the sol-gel transition which is thereafter reinforced upon further incorporation of casein particles.

Sludge from a slaughter-house wastewater plant, and mixtures of bulking agent (crushed wood pallet) and sludge were studied by Nuclear Magnetic Resonance (NMR). The NMR spin–spin relaxation ( T 2 ) and spin–lattice relaxation ( T 1 ) signals for sludge, wet crushed wood pallet and mixtures of sludge and bulking agent were decomposed into three relaxation time components. Each relaxation time component was explained by a non-homogeneous water distribution on a microscopic length scale and by the porosity of the material. For all samples, the T 2 relaxation time value of each component was directly related to the dry matter content. The addition of wet crushed wood to sludge induced a decrease in the relaxation time, explained by water transfer between the sludge and the wood. Magnetic Resonance Imaging (MRI) and respirometric measurements were performed on sludge and wood mixtures. MR images of the mixtures were successfully obtained at different biodegradation states. Based on specific NMR measurements in an identified area located in the MRI cells, the results showed that grey levels of MR images reflected dry matter content. This preliminary study showed that MRI would be a powerful tool to measure water distribution in sludge and bulking agent mixtures and highlights the potential of this technique to increase the understanding of sludge composting.

Publication Inra prise en compte dans l'analyse bibliométrique des publications scientifiques mondiales sur les Fruits, les Légumes et la Pomme de terre. Période 2000-2012. http://prodinra.inra.fr/record/256699; International audience; Magnetic Resonance Imaging (MRI) was performed on tomato fruit during two 3-week periods of postharvest ripening. Different image types were acquired to study macroscopic and microscopic structural changes. Air spaces were identified close to seeds and their shrinkage during the ripening period was estimated from the spin echo images. The development of the bubbles in the outer pericarp during ripening was estimated from the ratio of the long- and short-echo time gradient echo MRI images and supported by the macrovision imaging. Variations in the transverse (T2) and longitudinal (T1) relaxation times were determined from quantitative MRI images. They depended on the tissue type and matched fairly well between fruit. In the core, placenta, radial and outer pericarp, T2 decreased by about 25% from the initial values and T1 by about 25-30% from the initial values during postharvest ripening. In the locular tissue the relaxation times had less marked trends than in other tissues: both T2 and T1 increased slightly until the eighth or ninth measurement day and after that it returned to its approximate initial value. Multi-component characteristics of T2 and T1 decay were investigated by Nuclear Magnetic Resonance (NMR) relaxometry. They provided information about all major sub-cellular compartments and showed there was water redistribution among compartments during ripening. In addition to the relaxometry measurements, water content, weight loss and concentration of neutral sugars and acids were measured on some of the tomato fruit. Cell size and organization were investigated by macrovision experiments. Although the overall dependence of the relaxation time on tissue type was to some extent explained by chemical composition and cell dimension, no relationships between trends in MR data and tissue properties were established.

The aim of this study was to undertake a dynamic and quantitative evaluation of the local evolution of porosity in a section of bread using magnetic resonance imaging (MRI). A prototype of an oven compatible with continuous MRI acquisition had been previously developed and installed in the probe of the imager. Oil microcapsules, which provide a very different MRI signal to that obtained from the dough, were also incorporated in the dough before proving, and their position in the bread was monitored throughout baking. Microcapsules delimited dough layers of which initial thickness ranged from 7 to 20 mm. Monitoring of the expansion of these layers is presented and discussed. Local expansion of the lower part of the bread predominated, contributing to 82% of the overall expansion at an oven air temperature of 130 °C. This was related to a slight escape of gas in this region, favored by one-dimensional heat transport. When the crust was formed early, as for an oven air temperature of 182 °C, local expansion did not cease with the crust setting and occurred to the detriment of the other regions, which were compressed.

MRI thermometry methods are usually based on the temperature dependence of the proton resonance frequency. Unfortunately, these methods are very sensitive to the phase drift induced by the instability of the scanner which prevents any temperature mapping over long periods of time. A general method based on 3D spatial modelling of the phase drift as a function of time is presented. The MRI temperature measurements were validated on gel samples with uniform and constant temperature and with a linear temperature gradient. In the case of uniform temperature conditions, correction of the phase drift proved to be essential when long periods of acquisition were required, as bias could reach values of up to 200 degrees C in its absence. The temperature uncertainty measured by MRI was 1.2 degrees C in average over 290 min. This accuracy is coherent with the requirements for food applications especially when thermocouples are useless.

Texture analysis methods quantify the spatial variations in gray level values within an image and thus can provide useful information on the structures observed. However, they are sensitive to acquisition conditions due to the use of different protocols and to intra- and interscanner variations in the case of MRI. The influence was studied of two protocols and four different conditions of normalization of gray levels on the discrimination power of texture analysis methods applied to soft cheeses. Thirty-two samples of soft cheese were chosen at two different ripening periods (16 young and 16 old samples) in order to obtain two different microscopic structures of the protein gel. Proton density and T2-weighted MR images were acquired using a spin echo sequence on a 0.2 T scanner. Gray levels were normalized according to four methods: original gray levels, same maximum for all images, same mean for all images, and dynamics limited to ± 3 . Regions of interest were automatically defined, and texture descriptors were then computed for the co-occurrence matrix, run length matrix, gradient matrix, autoregressive model, and wavelet transform. The features with the lowest probability of error and average correlation coefficient were selected and used for classification with 1-nearest neighbor ( ) classifier. The best results were obtained when using the limitation of dynamics to ± 3 , which enhanced the differences between the two classes. The results demonstrated the influence of the normalization method and of the acquisition protocol on the effectiveness of the classification and also on the parameters selected for classification. These results indicate the need to evaluate sensitivity to MR acquisition protocols and to gray level normalization methods when texture analysis is required.; Les methodes d`analyse de texture quantifient les variations spatiales des niveaux de gris dans les images et peuvent fournir ainsi des informations pertinentes sur les structures observées. Cependant elles sont sensibles aux conditions d`acquisition liées aux différents protocoles et aux variations intra et inter scanner dans le cas de l`imagerie par résonance magnétique nucléaire. L`influence de deux protocoles et de quatre types de normalisation des niveaux de gris sur l`analyse de texture de différents types de fromages à pâte molle a été étudiée en particulier sur ses capacités de discrimination . Trente deux échantillons de fromages à pâte molle ont été choisis à deux stades d`affinage différents (16 jeunes et 16 vieux) afin d`obtenir deux gels de structures différentes. Des images pondérées en densité de proton et en T2 ont été acquises avec une séquence écho de spin sur un IRM 0.2 T. Les niveaux de gris ont été normalisés suivant quatre méthodes : aucune normalisation, même moyenne pour toutes les images, même maximum pour toutes les images et une dynamique limitée à ± 3 . Des zones d`intérêts ont été automatiquement définies et les descripteurs de textures ont été calculés en utilisant la matrice de cooccurence, la matrice des longueurs de plage, la matrice des gradients, un modèle autorégressif et la transformée en ondelette. Les paramètres les plus discriminants étaient sélectionnés et utilises pour la classification avec l`algorithme du plus proche voisin. Les meilleurs résultats furent obtenus avec la normalisation des niveaux de gris utilisant la dynamique ± 3 qui augmentait la différence entre les deux classes. Les résultats ont mis en évidence l`influence de la méthode de normalisation des niveaux de gris et du protocole d`acquisition sur les performances de la classification ainsi que sur les paramètres les plus discriminants. Ces résultats indiquent la nécessité d`évaluer la sensibilité au protocole et à la normalisation des niveaux de gris quand l`analyse de texture est utilisée.

DSC profiles and relaxation NMR 1H signals were used to characterise highly hydrated milk protein dispersion (3 to 20 g per 100 g DM) with various micellar casein concentrations (3-15 g per 100 g of dispersion), whey protein concentrations (9-3 g per 100 g of dispersion), lactose concentrations (0-7.5 g per 100 g of dispersion), CaCl2 concentration (0-2 mM) and pH(6.2-6.6). Results obtained with both techniques showed the predominant effect of micellar casein and lactose concentrations on the water state. Heat of fusion of water and amount of unfreezable water (0.49 g/g for dispersions without lactose and 0.60 g/g for lactose containing dispersions) measured by DSC varied mainly in lactose and native phosphocaseinate (NPQ) content. Furthermore, NMR water relaxation behaviour was consistent with a three site relaxation model. Because of fast diffusive exchange, the relaxation rate observed was the sum of the free water relaxation rate, the hydration water relaxation rate and the exchangeable protons relaxation rate, weighted by their relative proportions. Analysis of the variation in relaxation rate with the sample composition confirmed that the hydration water was mainly influenced by the casein concentration and that the chemical exchange effect, such as the lactose effect, could be attributed to soluble macromolecules. NMR versus DSC results were also discussed.; Les profils DSC et signaux de relaxation NMR 1H ont été utilisés pour caractériser la dispersion de protéine de lait très hydraté (3 à 20 g/DM) avec des concentrations de caséine micellaire variées (3-15 g/100g de dispersion), concentration de protéines de petit lait (9-3 g/100g de dispersion), concentration en lactose (0-7.5 g/100g de dispersion), concentration en CaCl2 (0-2 mM) et pH (6.2-6.6). Les résultats obtenus avec les deux techniques montrent l'effet prédominant des concentrations en caséine micellaire et lactose sur l'état de l'eau. La température de fusion de l'eau et la quantité d'eau non gelable (0.49 g/g pour les dispersions sans lactose et 0.60 g/g pour les dispersions contenant du lactose) mesuré par DSC variaient essentiellement en lactose et contenu en phosphocaseinate natif (NPQ). De plus, le comportement de relaxation de l'eau en NMR était consistant avec un modèle de relaxation de trois sites. A cause d'une diffusion rapide, le taux de relaxation observé est la somme du taux de relaxation de l'eau libre, de l'eau d'hydratation et des protons échangeables pondérés par leurs proportions relatives. L'analyse de la variation dans un taux de relaxation avec la composition échantillon a confirmé que l'eau d'hydratation était essentiellement influencée par la concentration en caséine et que l'effet de l'échange chimique, tel que l'effet du lactose, pourrait être attribué à des macromolécules solubles. Les résultats de NMR vs. DSC sont aussi discutés.