Cuisson de pain sous vide partiel à basse température

International audienceAn experimental approach of partial baking of dough rolls at low temperature and under partial vacuum was developed. In contrast to previously applied vacuum to bread dough e.g. Bell et al. (1981) or Gandikota et al. (2004), vacuum was applied simultaneously to heating to set the dough structure. In conventional baking, dough inflation is driven by the increase in temperature which favours the release of gases into gas cells of dough and the adiabatic expansion of gas. As deformable to a large extent, the dough expands without a high increase in pressure within gas cells (2 kPa at most). Under partial vacuum baking, the decrease in external pressure and temperature are combined. In the present study, Magnetic Resonance Imaging (MRI) scanning of dough baking under vacuum conditions made it possible to separate the contribution of the temperature increase and partial vacuum to the overall inflation during baking. With moderate vacuum, rolls were found to be 20% more expanded than those baked using a conventional convection oven. Examination of MRI scans acquired just after vacuum application also concluded to uniform repartition of gas fraction through the dough section. As early crust setting interferes with the crumb setting e.g. Wagner et al. (2008), heat flux should be limited at the beginning of baking in order to delay the drying process as well as the setting of the periphery; ideally crust setting should occur after bubble inflation at the dough core had occurred. Provided that low drying rates were managed, partial vacuum baking could possibly favor bubble inflation throughout the crumb well before the setting of the peripheral layers. This was illustrated in the present study by varying the oven temperatures

Water transport during bread baking: Impact of the baking temperature and the baking time

International audienceThe impact of the baking temperature on the moisture profile (in terms of water content), during bread baking was analyzed using a convection oven (three oven temperatures and different baking times). During baking, local water content and temperature were measured at different regions of the crust and crumb. There was found an increase in water content at the core. Water content reached a maximum level (at about 2.5%), with no effect of the baking temperature, and decreased slowly at advanced baking times. Regarding the crust, a theoretical model relating water flux to the driven force (temperature difference between the oven environment and the vaporization front) and the crust thermal resistance was validated with experimental values. Water losses were also reported. The water lost by bread contributes significantly to the energy consumption by this process and its reduction is of concern for conducting the process in a more sustainable manner. A better optimization of heat transfer between the surface (for coloration purposes) and the core (for inflation purposes) could help in this way, together with shorter baking duration and hence higher yield. © The Author(s) 2018

Characterization of gluten-free bread crumb baked at atmospheric and reduced pressures using TD-NMR

International audienceThis research aimed to study the effects of using a partial vacuum for bread baking on macromolecules and water distribution in gluten-free bread. Bread baking under partial vacuum results in greater oven rise and a larger gas fraction in the crumb. Because water's boiling point decreases under reduced pressure, it was expected that its distribution within the dough and its interactions with the others dough's constituents (mainly starch) would differ from those in bread baked under atmospheric pressure. Time-domain nuclear magnetic resonance was used, as it has the rare capacity to quantify both gelatinization and retrogradation of starch. Complementary rheological measurements made it possible to show that crumb Young's modulus was mostly influenced by the gas fraction whereas there was little change in starch gelatinization and retrogradation when dough was baked under partial vacuum. When insufficiently hydrated (48%), the volume of breads was practically the same whatever the baking process. Meanwhile, the nuclear magnetic resonance results suggested that amylose short-term crystallization (on cooling) is dependent on water content. In addition, crumb Young's modulus during storage at room temperature correlated with an increase in free induction decay signal intensity. © 2019 John Wiley & Sons, Ltd

Gluten-free bread baked under reduced pressure characterized by TD-NMR

International audienceBased on spin-spin T2 relaxation time measurements, the time-domain NMR (TD-NMR) spectroscopy has been used to provide relevant information on the water and biopolymer motion and transfer in bread [1]. This technique permits to characterize molecular interaction and transformations in a non-invasive and non-destructive way, in real time during a process (heating, freezing, hydration ...). In bread, proteins of gluten when hydrated form a viscous mass that confers to the dough, structure, viscosity, mixing tolerance and gas holding ability [2]. On the other hand, starch, in presence of water and increasing temperature, undergoes a series of changes known as swelling, gelatinization and retrogradation that induce variations in water distribution, in starch structure and interactions between them [3]. This study aimed at understanding and ranking the contribution of these biochemical transformations that contribute to the crumb structure and the textural properties of bread prepared with a gluten free mix (Schär). The water transfers and the extent of starch gelatinization in crumb were studied by TD-NMR after the heating/cooling process of dough hydrated at 55% and 48% (wet basis). Two baking processes were compared, one at the atmospheric pressure while the other was carried out at reduced pressure (-20 kPa). Bread baking using partial vacuum results in greater oven-rise and greater gas fraction in the crumb, giving an increased softness of the crumb for a more pleasant mouthfeel. Under reduced pressure, the boiling point of water decreases but, until now, no study was conducted to check if this baking condition modifies or not the starch gelatinization and protein denaturation. By comparing rheological measurements (modulus of elasticity using a compression stress relaxation experiment) with TD-NMR data, it was shown that the crumb softness was mostly driven by the gas fraction while the biochemical changes (starch gelatinization, protein denaturation), monitored by TD-NMR, were little modified when dough was baked under partial vacuum

Overall and Local Bread Expansion, Mechanical Properties, and Molecular Structure During Bread Baking: Effect of Emulsifying Starches

International audienceIn order to determine the relationship between molecular structure of wheat bread dough, its mechanical properties, total and local bread expansion during baking and final bread quality, different methods (rheological, nuclear magnetic resonance, magnetic resonance imaging and general bread characterisation) were employed. The study was extended on wheat dough with starch modified by octenyl succinic anhydride (OSA) in order to generalise the results. The interest of investigating multi-scale changes occurring in dough at different phases of baking process by considering overall results was demonstrated. It was found that OSA starch improved the baking performance during the first phase of baking. This feature was due to a higher absorption of water by OSA starch granules occurring at temperatures below that of starch gelatinization, as confirmed by NMR, and consecutive higher resistance to deformation for OSA dough in this temperature range (20'60 °C). This was explained by a delayed collapse of cell walls in the bottom of the OSA dough. In the second phase of baking (60'80 °C), the mechanism of shrinkage reduced the volume gained by OSA dough during the first phase of baking due to higher rigidity of OSA dough and its higher resistance to deformation. MRI monitoring of the inflation during baking made it possible to distinguish the qualities and defaults coming from the addition of OSA starch as well as to suggest the possible mechanisms at the origin of such dough behaviour. © 2016 Springer Science+Business Media New Yor

Artificial intelligence solution to classify pulmonary nodules on CT

International audienceThe purpose of this study was to create an algorithm to detect and classify pulmonary nodules in two categories based on their volume greater than 100 mm3 or not, using machine learning and deep learning techniques

Three artificial intelligence data challenges based on CT and MRI

International audiencePurpose: The second edition of the artificial intelligence (AI) data challenge was organized by the French Society of Radiology with the aim to: (i), work on relevant public health issues; (ii), build large, mul-ticentre, high quality databases; and (iii), include three-dimensional (3D) information and prognostic questions. Materials and methods: Relevant clinical questions were proposed by French subspecialty colleges of radiology. Their feasibility was assessed by experts in the field of AI. A dedicated platform was set up for inclusion centers to safely upload their anonymized examinations in compliance with general data protection regulation. The quality of the database was checked by experts weekly with annotations performed by radiologists. Multidisciplinary teams competed between September 11 th and October 13 th 2019. Results: Three questions were selected using different imaging and evaluation modalities, including: pulmonary nodule detection and classification from 3D computed tomography (CT), prediction of expanded disability status scale in multiple sclerosis using 3D magnetic resonance imaging (MRI) and segmentation of muscular surface for sarcopenia estimation from two-dimensional CT. A total of 4347 examinations were gathered of which only 6% were excluded. Three independent databases from 24 individual centers were created. A total of 143 participants were split into 20 multidisciplinary teams. Conclusion: Three data challenges with over 1200 general data protection regulation compliant CT or MRI examinations each were organized. Future challenges should be made with more complex situations combining histopathological or genetic information to resemble real life situations faced by radiologists in routine practice