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Abstract

Partially dehydrated tomato gels are innovative food products of extended shelf life for using in snack preparations. Flexible, sheet-shaped product was obtained by a pectic gelation mechanism induced by dehydration, starting from a formulation based on tomato puree. The drying kinetics of this product was studied in a bench-scale tray dryer operating between 40 and 80 °C at an air velocity of 2m/s. The `in-dryer' weighings of the trays allowed accurate experimental data to be recorded. The observed drying curves were modeled in two stages: for high moisture contents, with a constant drying rate model while at lower moistures, with an analytical-diffusive model, solved for the average sheet thickness. The mass-transfer Biot number in the diffusive model was found to be 1.1, indicating that external and internal resistances to mass-transfer are comparable. An Arrhenius model correctly described the temperature dependence of the water diffusion coefficient in the tomato pectic gel, represented by an activation energy of 22.0 kJ/mol. The model can be used to estimate minimum drying times and can be incorporated in tray dryer simulators for computer prototyping of new designs, and optimization of existing drying facilities.

Keywords

tomato pectic gels drying kinetics modeling

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A Mass-Transfer Model for the Drying of an Innovative Tomato Gel

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