Drying kinetics of thin food ingredient films in Electrohydrodynamic drying – experimental and mechanistic modelling

Electrohydrodynamic (EHD) drying is a promising alternative to conventional drying methods, offering reduced energy consumption and lower operating temperatures. These characteristics make it particularly suitable for heat-sensitive materials, such as food products. The technique relies on corona wind generated by high voltage applied to a sharp emitter electrode to remove moisture from a wet product placed on a collector electrode. To support large scale implementation of EHD drying, reliable predictive models are essential. This study presents mechanistic models for EHD drying of thin food films, using maltodextrin and starch as representative systems. The maltodextrin model was based on moisture transport within a polymer solution, while the starch model accounted for effective moisture diffusion in porous media. Both models incorporated mass and heat transfer principles, and in a later stage, the possible contribution of Ohmic heating was incorporated into the model. Their predictive performance was validated and compared against experimental data, with convective mass transfer coefficients and internal diffusivities estimated through parametric fitting using least squares minimization. All models accurately predicted the experimentally observed drying behaviour. The simulations suggest that for slurries of ungelatinized starch, the Ohmic heating effect become more pronounced for films with a thickness of >1 cm. For thinner films, such as studied in our experiments, the Ohmic heating effect is negligible. Therefore, using simplified models without Ohmic heating is adequate for predictive purposes, reducing complexity, data requirement, and computational cost.