Crack in rusks: modelling and simulation of stress and displacement fields

International audienceCrack during storage is a recurrent problem in the dry cereal products industry (rusks, biscuits, crackers...). The aim of this work is to understand how mechanical stresses develop during storage. For this purpose, a model was developed with Comsol Multiphysics to visualize the changes of the water content and of the stress and displacement fields during one week of storage. The parameters required for the modelling are in particular the mass diffusivity, the hygrometric expansion coefficient, the Young's modulus and the Poisson's ratio of rusk. Specific measurement methods were developed to obtain these data such as a dilatation bench and observation of the material undergoing compression test. A first model was developed assuming an isotropic material. The results showed that the water content is almost equalized throughout the rusk over one week of storage. A second model including the presence of cells in the structure showed that the stresses tend to be higher around the cells. The rusk tends to shrink during storage with small strain. The calculated stress reach high values close to the rupture stress. As a conclusion, rusk breakage seems to be closely linked to the cellular structure of the crumb of the bread used to produce rusk. The mitigation of rusk crack requires a good control of the uniformity of the cellular structure of the crumb without large cells

Cracking of rusks during storage: stress and strain simulation

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Assessing the permittivity of an unsaturated sand by combining a Lattice Boltzmann Method simulation, electromagnetic homogenization models and measurements

International audienceDielectric permittivity is a prevailing property used for the estimation of water content in heterogeneous materials like soils and concrete. Troubles are frequently encountered when searching for the relationship between a material's permittivity and its degree of saturation. Building an electromagnetic model of the material is thus of critical importance. This paper focuses on the study of an unsaturated sand. Analytical and numerical electromagnetic homogenization procedures are confronted. Dielectric permittivity of the sand is measured at different saturation degrees within the frequency range [200 MHz; 1 GHz] thanks to a large open-ended coaxial probe. A numerical procedure is then built to calculate the effective permittivity of the medium. First, a representative elementary volume of the dry sand is created. Pore domain is then separated into water and gas phases through the use of a Lattice Boltzmann Method algorithm. The effective permittivity is then estimated using numerical homogenization. Results obtained at different water contents were eventually compared with analytical homogenization models like the Bruggeman and Maxwell-Garnett equations. A close match is obtained between measurements, numerically derived results and a Bruggeman model based on a spheroidal description of the air and water phases

Impact of waiting time before baking and amount of baking powder on aeration during kneading, oven rise and final porosity of pound cake

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Forced-air cooling of dairy product in pallets: influence of process parameters on energy and quality

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Changes in specific heat and thermal conductivity of hydrothermal treated maize starch

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Prediction of thermal conductivity and specific heat of native maize starch and comparison with HMT treated starch

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Prediction of thermal conductivity and specific heat of native maize starch and comparison with hydrothermal treated starch

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Water monitoring in biscuits by Near Infrared Hyperspectral imaging

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Water monitoring in biscuits by Near Infrared Hyperspectral imaging

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