Model discrimination for drying and rehydration kinetics of freeze‐dried tomatoes

The aim of this work is to investigate the effect of a highly interconnected porous microstructure on the quality of rehydrated tomatoes by (a) designing a freeze-dried cycle that ensure product integrity (i.e., no collapse, no puffing) (b) characterizing both freeze-drying and rehydration kinetics. Fresh tomatoes were first freeze-dried and subsequently rehydrated to get generate kinetics data. Afterwards, six thin-layer drying models and four rehydration models were fitted using regression analysis to the experimental data. The goodness-of-fit was evaluated according to root mean squared error, adjusted R-2, Akaike information criterion, and Bayesian information criterion. The most accurate representations of the system kinetics were observed using the Page model for freeze-drying and the exponential and Weibull models for rehydration. Rehydration capacities and equilibrium moisture contents of the rehydrated samples were found to increase with temperature, and the corresponding activation energy values were calculated. Practical applications Freeze-dried porous microstructures can enhance water absorption and transport, contributing to restore the fresh product functional properties and leading to higher quality rehydrated products, especially in highly heat-sensitive food products as vegetables and fruits. The use of mathematical models to (a) design freeze-drying cycles and (b) characterize and/or predict drying and rehydration kinetics in cellular freeze-dried microstructures is then key for processing and optimization of convenience and ready-to-eat foods, which represents the main application of dried foods/powders and also a growing market. This approach to the manufacture of freeze-dried products also presents potential to set the basis of an alternative decentralized supply scenario for high-quality dried products, where freeze-dried foods will be manufactured and shipped and finally rehydrated closer to the consumption point.