Ohmic heating applied to the baking process: experimental and numerical approaches

International audienceThis work aims at studying the feasibility of ohmic heating (OH) technology applied to the baking process. The method includes proofing (fermentation) and baking and leads to the production of crustless sandwich bread without the need of cutting the crust away, in a shorter time and with theoretically lower energy costs than conventional baking. An ohmic cell was made to study the electrical conductivity (EC) of bread dough under different experimental conditions. The results showed that the EC increased linearly with the temperature, except during the starch gelatinization stage (60 – 76 °C) because of the bounding of water. The EC decreased with the porosity of the dough when fermented by yeasts, and drastically decreased with the reduction of salt content in the dough, showing the need to control the product formulation. An ohmic baking oven monitored by a PLC was developed to perform both proofing and baking in the same apparatus. The results showed that using OH to quickly reach the optimal temperature of yeast activity (35 °C) significantly reduced the lag phase and shortened the total proofing time. A numerical model was developed and validated by experimental results, taking into account heat and water (vapour and liquid water) transfers. The results confirmed the importance of temperature gradients between the surface of the electrodes and the core of the product, first observed by the underbaked aspect of the bread loaf on its sides. Different baking scenarios and their impacts on temperature and water content gradients were modelled

Development of ohmic cells dedicated to the baking of crust-less bread

International audienc

La salud enfermedad como hecho social: un nuevo enfoque

International audienceBread dough baking was investigated using ohmic heating technology. An experimental system was set up for the measurement of the electrical conductivity of bread dough during heating. The influence of temperature, salt content and degree of fermentation (porosity) on the electrical conductivity of dough was investigated. It was observed that it increased linearly with temperature, until starch gelatinisation during which the dough conductivity remained constant or slightly decreased. The conductivity increased linearly again after starch gelatinisation, but at a lower rate. The electrical conductivity of dough had a linear positive dependence on salt content, but decreased with increasing dough porosity. Numerical simulations of temperature increase were carried out and compared with experimental data. For a good correlation between numerical and experimental data, a corrective coefficient was numerically estimated and validated, taking into account mainly the conversion of electrical energy to heat, and geometric uncertainties. Numerical results showed that the linear evolution of temperature with heating time was mainly caused by heat losses

Baking of bread with ohmic heating technology; a review proposing new horizons for crust less bread with low energy demand

International audienc

Sandwich bread baking by ohmic heating

International audienc

Cuisson d’une pâte céréalière par chauffage ohmique : mise en place d'un modèle numérique et validation expérimentale

International audienc

Ohmic baking; a review based on recent investigations for crustless bread production

International audienc

Ohmic heating applied to the baking process: experimental and numerical approaches

International audienceThis work aims at studying the feasibility of ohmic heating (OH) technology applied to the baking process. The method includes proofing (fermentation) and baking and leads to the production of crustless sandwich bread without the need of cutting the crust away, in a shorter time and with theoretically lower energy costs than conventional baking. An ohmic cell was made to study the electrical conductivity (EC) of bread dough under different experimental conditions. The results showed that the EC increased linearly with the temperature, except during the starch gelatinization stage (60 – 76 °C) because of the bounding of water. The EC decreased with the porosity of the dough when fermented by yeasts, and drastically decreased with the reduction of salt content in the dough, showing the need to control the product formulation. An ohmic baking oven monitored by a PLC was developed to perform both proofing and baking in the same apparatus. The results showed that using OH to quickly reach the optimal temperature of yeast activity (35 °C) significantly reduced the lag phase and shortened the total proofing time. A numerical model was developed and validated by experimental results, taking into account heat and water (vapour and liquid water) transfers. The results confirmed the importance of temperature gradients between the surface of the electrodes and the core of the product, first observed by the underbaked aspect of the bread loaf on its sides. Different baking scenarios and their impacts on temperature and water content gradients were modelled

3D Numerical modelling of crustless bread baking with ohmic heating technology

International audience(Your abstract must use Normal style and must fit in this box. Your abstract should be no longer than 300 words. The box will 'expand' over 2 pages as you add text/diagrams into it.) Ohmic heating (OH) is an electromagnetic based method, in which an electric current is passed through a foodstuff in order to heat it up by its own electrical resistance. Its main advantages are the possibility to reach very high heating rates, the absence of thermal inertia (instant shut-off of the system) and its volumetric heating, leading to a very high energy efficiency. If OH is already used in the food industry for the heat treatment of liquid products in continuous processes, its application to solid foodstuffs in batch production is scarce and even non-existent in the case of bread baking. To check the baking and the quality of bread, temperature and water content have to be evaluated during ohmic heating. Because non intrusive measurement of such characteristics is difficult and/or onerous, numerical simulation is viewed as a very interesting tool. In this work, a 3D numerical model was developed to study the heat and mass transfer in a commercial-sized crustless sandwich bread. The objective was to locate the sensitive spots (high and low temperature locations) during a potential industrial baking and to know more about the impact of the process on the final water content of the product. The model was validated by experimental tests realized on a prototype (figure 1) developed in our lab [1] and provided a quite good accuracy in terms of temperatures (figure 2) and water contents. Especially, numerical results have shown that there could be strong temperature gradients close to the electrodes and that the distribution of moisture content was the inverse of that resulting from a conventional heating. [1] T. Gally, O. Rouaud, V. Jury, M. Havet, A. Ogé, and A. Le-Bail, " Proofing of bread dough assisted by ohmic heating, " Innov

Coupled heat and mass transfer model dedicated to bread baking with ohmic technology

National audienc