A model-based study of rehydration kinetics in freeze-dried tomatoes

Characterising rehydration kinetics is key to understand the effect of microstructure on the quality of rehydrated products. Well-connected porous networks, like the ones created by freeze-drying processes, can enhance water absorption and transport, leading to higher final quality rehydrated products. Such products present the basis for a novel distribution scenario for (freeze-)dried products that are rehydrated closer to the consumption point. In this work, fresh tomatoes were first freeze-dried and subsequently rehydrated at different temperatures. Four rehydration models were fitted to the experimental data using regression analysis. The goodness-of-fit was evaluated according to (i) Root Mean Squared Error (ii) adjusted R-square (iii) Akaike Information Criterion (iv) Bayesian Information Criterion. The Exponential and Weibull models provided the most accurate descriptions of the rehydration kinetics. The effect of temperature on rehydration kinetics was also evaluated, with rehydration capacities and equilibrium moisture contents of the rehydrated tomatoes increasing with temperature. In addition, activation energy values for rehydration, which were in accordance with the existing literature values, were also obtained from the fitted rehydration rate parameters.