Water sorption isotherms and air-drying kinetics modelling of Andean tubers and tuberous roots

In recent years, scientific research has focused on studying Andean roots and tubers due to their attractive agricultural and nutritional qualities; however, as they contain high moisture, it is imperative to dehydrate them to extend their useful life. Likewise, the analysis of dry food's drying kinetics and food stability (in terms of water activity) is essential to control moisture removal and marketing progress. The drying process carried out in this study (65ºC for 8 hours) showed three clear stages: adaptation, the drying period at a constant speed, and a third stage with a gradual drop in the drying rate. The experimental data were satisfactorily adjusted to seven mathematical models, highlighting the Page model since it presented higher coefficient of determination values. Likewise, the estimated mean error and percentage of relative mean deviation values were less than 1 in this model. The isotherms showed a type II sigmoidal shape, representing the samples are hygroscopic due to the structural changes suffered by the matrix during the process. Finally, the GAB model showed a higher coefficient of determination. All the Andean tubers and tuberous root flours must be dried until reaching a humidity below 10 g_water/g_{dry mass} and stored in environments with a relative humidity lower than 60% to remain stable for longer.