Contour Fitting of Fused Filaments Cross-Section Images by Lemniscates of Booth: Application to Viscous Sintering Kinetics Modeling

International audienceA method for image analysis was implemented to determine the edge pixels of two biopolymer-based thermoplastic filaments during their hot melt isothermal sintering at 120 ◦C. Successive inverted ellipses are adjusted to the contour of the sintered filaments and lead to the identification of the parameters of the corresponding lemniscates of Booth. The different steps of the morphological image analysis are detailed, from 8-bit coded acquired images (1 frame/s), to the final fitting of the optimized mathematical functions describing the evolution of the filaments envelope. The complete sequence is composed of an initial pure viscous sintering step during the first minute, followed by viscoelastic swelling combined with melt spreading for a longer time, and then the stabilization of the sintered filaments shape for over 2 min at high temperatures. Using a master curve obtained from Hopper’s abacus, the characteristic viscous sintering time is assessed at tvs = 78 s, confirming the one previously found based on the measurement of the bonding neck length alone. Then, the full description of the evolution of the thermoplastic filaments envelope is assessable by image analysis during sintering trials as a result of its digital modeling as successive lemniscates of Booth, reflecting geometry changes in the molten state

Studying dough behaviour by implementing different formulations and processing conditions during bread making process

International audienceCurrent study was designed to study the dough behaviour during bread making process and to assemble the existing knowledge on available models in order to develop new and innovative Basic Knowledge Models (BKM) for controlling dough formation and baking. Nine different formulations were optimised, with products varying from pan bread to sweet dough (brioche) were developed and mixed in a spiral mixer at a speed varying from 80-160 rpm, for maximum duration of 15 min. The specific mechanical energy Es delivered, and the dough temperature Td were continuously observed and varied from 30 to 42 kJ/kg and from 24 to 27 ºC, respectively. The evolution of porosity (≤ 0.80) and stability curves, which were determined through video image analysis for 180 min, indicated that the dough stability (0.48-0.75) is more influenced by dough rheological properties. Likewise, effect of dough formulation on thermo-viscoelastic behaviour (small deformation) was evaluated by dynamic mechanical analysis (DMA) and variations of the ratio, of maximum (100 ºC) to minimum elastic modulus (70 ºC), was interpreted with relation to gluten development which ranged between 13-28. In this regard, lubricated squeezing flow analysed the bi-extensional properties at large deformation which demonstrated that the variation in ingredients significantly influences the flow curves and strain hardening index. A specific protocol was developed to determine the dough stickiness, where the presence of butter and eggs influenced the dough adhesiveness. These experimental results will be applicable to other kinds of dough during preparation of different bakery products. The scientific results will also be compared with those obtained by the baking experts, thus enabling us to extend the industrial know-how and professional knowledge

Bread - pan interface; impact of crust structure on bread demolding

International audienc

Evaluation rhéologique de pâtes boulangères et relation avec leur comportement au cours de la fermentation

International audienceLes conditions de pétrissage de la farine de blé mélangée aux ingrédients (sucre, beurre, œufs) influencent le comportement de la pâte au cours des étapes successives (fermentation, formage, etc) d’élaboration de divers produits de boulangerie. La connaissance du comportement rhéologique de la pâte a permis de modéliser le pétrissage de la pâte et la fermentation pour une formulation simple (farine + eau, i.e. pain français). Pour étendre ces modèles à différentes recettes, représentatives des produits de boulangerie, t.q. pain de mie et brioche, il est nécessaire de déterminer leurs propriétés rhéologiques, y compris les propriétés d'adhésion.Neuf pâtes de compositions différentes, contenant différentes quantités d'œufs (< 42% base farine), de sucre (<12%) et de beurre (< 20%) ont été pétries (15 min), à des vitesses différentes (80-160 tr / min) conduisant à diverses énergies spécifiques (30 ≤ Es ≤ 42 kJ / kg), et à des températures finales Td variant de 28 à 24 ° C, avec l’ajout de beurre. Ces variations suggèrent des modifications de la structure du réseau de gluten, qui ont été confirmées par les changements du rapport des modules de stockage E’ (13 à 28) déterminés, par analyse thermomécanique dynamique (DMA), avant et après la réticulation du gluten qui survient entre 55 et 70 ° C. À grande déformation (1), la viscosité bi-extensionnelle, déterminée par le test de compression uniaxiale en conditions lubrifiées (LSF), suit une loi de puissance, à partir de laquelle un indice de consistance K est déduit. Les valeurs de K décroissent de 8 à 3 kPa.sn, avec l’ajout de sucre. Les suivis, par imagerie, de levée de la pâte en cours de fermentation montrent que la température Td gouverne l’amplitude des cinétiques de porosité et de stabilité de la pâte, tandis que la consistance K est inversement reliée au temps caractéristique de la porosité. Enfin, les propriétés d’adhérence des pâtes ont été mesurées par un test de compression-retrait. Les variations des différences de forces normales (3,9-8,9 N) et de travail d’adhésion (5-15mJ) sont essentiellement liées à la consistance. Ces résultats sont confrontés à la connaissance existant de façon éparse, notamment dans le domaine professionnel, pour proposer des modèles élémentaires de connaissance, dont l’application au procédé favoriserait la conception d’aliments aux propriétés ciblées

Bread collapse. Causes of the technological defect and impact of depanning time on bread quality

International audienceThe collapse of the sides of sliced bread is a technological problem for the baking industry. This study aims to understand the possible link between bread structures, internal pressure gradient, waiting time in the pan before depanning, and side collapse. The collapse variation was measured using laser to get bread profiles, and using image analysis of bread slices. The pressure variation at the centre and at the periphery was measured, and the product structure was observed using X-ray microtomography. The collapse increases with the cooling time in pan. The pressure in the cells is always higher than pressure in ambiance and cannot explain the collapse. The bread structure measurements indicate that the collapse is probably due to the cells shrinking of bread sides cells. A complementary explanation is to be searched in the specific volume variation of the material constituting the dough and the bread during the baking and the cooling

Viscosity of artificial bolus of high protein extruded snacks

Pulse legumes (pea, lentil, faba bean) are excellent source of proteins (20-30% db), dietary fibers (10-30%), and starch (40-55%). The formulation of gluten-free extruded snacks made entirely from pulse legumes is an interesting way to introduce legumes to young people. Due to the reactivity of protein components under thermomechanical treatment, extrusion can produce cellular structures with various texture and starch-protein composite morphology. In turn, the morphology of parietal material governs masticatory performances. For the first time, the interaction coefficient between bolus and saliva was determined by taking into account multi-scale structure of high-protein solid foams. The pea flour was extruded using a twin-screw extruder to obtain solid foams adapted to human mastication. Some samples were selected for in-vitro chewing by mapping the main properties: density, cellular architecture, texture, water absorption index (WAI) of starch and solubility of protein aggregates linked by S-S bonds in the dithiothreitol (DTE) using Principal Component Analysis. The boluses were collected at 3 chewing steps, representing different chewing times (t) until swallowing. The size distribution of bolus fragments was determined by imaging technique. Bolus consistency and water (“saliva”) uptake were determined by an adapted capillary rheometer, and gravimetric method, respectively. For all samples, the bolus viscosity exhibited shear thinning behaviour and it decreased with chewing time. Bolus flow index was quite constant for all chewing conditions and samples. However, bolus consistency index was correlated negatively to bolus water uptake (∆W) through a plasticization coefficient. Furthermore, ∆W could be predicted from theoretical salivary flow and median particle size. The model parameters depending on foams absorption properties could be expressed in function of WAI and protein solubility in DTE. The results will enrich the database for mechanistic modelling of proteinaceous solid foams chewing

Multi-scale structural changes of starch and proteins during pea flour extrusion

Dehulled yellow pea flour (48.2% starch, 23.4% proteins, d.b.), was processed by a twin-screw extruder at various moisture contents MC (18–35% w.b.), product temperature T (115–165 °C), and specific mechanical energy SME (50–1200 kJ/kg). Structural changes of extruded pea flour were determined at different scales by measurements of density (expansion), crystallinity (X-ray diffraction), gelatinisation enthalpy (DSC), starch solubility in water and protein solubility in SDS and DTE (SE-HPLC). Foam density dropped from 820 to 85 kg/m3 with increase in SME and T (R2 ≥ 0.78). DSC and XRD results showed that starch was amorphous whatever extrusion conditions. Its solubility in water augmented up to 50%. Increasing temperature from 115 to 165 °C decreased proteins soluble in SDS from 95 to 35% (R2 = 0.83) of total proteins, whereas the proteins soluble in DTE increased from 5 to 45% (R2 = 0.75) of total proteins. These trends could be described by sigmoid models, which allowed determining onset temperatures for changes of protein solubility in the interval [125, 146 °C], whatever moisture content. The SME impact on protein solubility followed similar trends. These results suggest the creation of protein network by Ssingle bondS bonds, implicating larger SDS-insoluble protein aggregates, as a result of increasing T and SME, accompanied by creation of covalent bonds other than Ssingle bondS ones. CSLM images suggested that extruded pea flour had a composite morphology that changed from dispersed small protein aggregates to a bi-continuous matrix of large protein aggregates and amorphous starch. This morphology would govern the expansion of pea flour by extrusion

Chewing behavior of high-protein expanded pea flour

Chewing behavior of high-protein expanded pea flour. 5. international conference on Food oral processin