Le chauffage ohmique pour optimiser la consommation énergétique de la production de pain de mie sans croûte

National audienc

Combination of imaging systems to understand checking and breakage of dry cereal products

International audienc

Proofing of bread dough assisted by ohmic heating

International audienceProofing of bread dough was studied under ohmic heating for a target temperature of 35°C. An experimental device based on PLC monitoring was developed to study the effect of heating rates and voltages on the proofing process. Conventional and ohmic heating-assisted proofing were compared; the results showed that the process itself had no impact on the proofing when identical heating rates (0.065°C·min −1) were used. However, increasing the heating rate could significantly reduce the time needed to reach an expansion ratio of 3 (from 122 min during conventional proofing to 65–70 min during ohmic heating in the range of 1–10°C·min −1). This was due to the shortening of the lag phase at the beginning of proofing (from 58 min during conventional heating to 20 min at 10°C·min −1 in ohmic heating). Results also showed that the voltage intensity had no significant effect on the proofing kinetics in the range of 50–150 V. The evolution of expansion ratios with proofing time could be fitted by a Gompertz model with a very high accuracy (R 2 N 0.999

Study of continuous cake pre-baking in a rectangular channel using ohmic heating

International audienceAn original device dedicated to additive manufacturing was developed to pre-bake cake batter. Its originality lies in the fact that pre-baking is ensured by ohmic heating implemented in a rectangular channel equipped with two parallel electrodes. Experiments and numerical studies were carried out and benchmarked. The rheological properties of the cake batter (non-Newtonian power-law fluid) and the influence of voltage and temperature on electrical conductivity were accommodated in the numerical model. Due to the low velocities of the very viscous products near the solid-liquid interface, it was found that the heterogeneity of the temperature at the nozzle outlet under continuous ohmic heating could lead to nozzle clogging when high temperatures are reached. Hot spots were identified in different areas of the channel, such as corners where the electric field is high and velocity is close to zero. A parametric study was performed on the impact of the thermophysical properties of the batter, showing that specific heat has a much greater impact than thermal conductivity on the accuracy of the tem-peratures computed. Analysis of the process parameters showed that a stronger electric field leads to a higher temperature gradient in the nozzle section. The temperature gradient decreases with electrode distance (delect) and nozzle width (l). This model could be used to optimize the ohmic heating nozzle configuration, with the objective of obtaining a continuous flow of pre-baked cake batter, while preventing clogging. Such a system could be used as 3D printing head. Industrial relevance: Conventional 3D printing of bakery products is based on the deposition of a batter, followed by a baking. This study proposes an innovative approach based on a printing nozzle equipped with ohmic heating, with the objective of achieving a uniform temperature distribution and of obtaining high mass flow rate. Despite a significant temperature gradient in the baked batter at the exit of the nozzle, the obtained results showed that adjusting the nozzle geometry allows a reduction of the gradient. Further investigations are thus needed to reduce the temperature gradient and to accommodate expansion of the batter in the case of formu-lation using baking powder. The transfer of such concept for industry application may be doable in a close future

Développement d'un procédé de précuisson de produit de panification en continu par chauffage ohmique

National audienc

Study of continuous pre-baking in a rectangular channel using ohmic heating

International audienc

Développement d'un procédé de précuisson de produit de panification en continu par chauffage ohmique

National audienc

Modelling rheological dough behaviour from an innovative air-puff system

International audienc

Unveiling the mechanism of the occurrence of breakage in biscuits during storage and means to mitigate this risk

International audienc

Evaluation of bread dough aeration during kneading by an air-jet impulse system

International audienc