Water-Sorption Isotherms and Air-Drying-Kinetics Modelling of Andean Tubers and Tuberous Roots

Abstract

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 a high level of moisture, it is imperative to dry them to extend their useful life. Likewise, analysing food-drying kinetics and food stability (regarding water activity) is essential to control moisture removal and the marketing progress. The drying process carried out in this study (65 °C for 8 h) showed three clear stages: adaptation, the drying period at a constant velocity, and a third stage with a gradual drop in the drying rate. The experimental data were satisfactorily adjusted to seven mathematical models, with the Page model highlighted since it presented higher coefficient-of-determination values. Likewise, this model estimated that the mean-error and percentage-of-relative-mean-deviation values were less than 1. The isotherms showed a type-II sigmoidal shape, showing that the samples were hygroscopic due to the structural changes undergone 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 gwater/gdry mass and stored in environments with a relative humidity lower than 60% to remain stable for longer.

Keywords

• ipomoea batatas
• tropaeolum tuberosum
• arracacia xanthorrhiza
• oxalis tuberosa