Moisture sorption isotherms and thermodynamic properties of isomaltulose-enriched mango

Moisture sorption isotherms and thermodynamic parameters are essential for designing and optimizing food processing and storage systems. This study aimed to evaluate these characteristics in untreated and osmotically treated mango slices, using isomaltulose and sucrose as osmotic agents. Moisture sorption isotherms were determined at temperatures ranging from 313.15 to 353.15 K using the static gravimetric method. The net isosteric heat of sorption was calculated using the Clausius-Clapeyron equation, along with differential enthalpy, entropy, and Gibbs free energy.

The sorption isotherms exhibited type II and III behavior. Microbiological stability was maintained at equilibrium moisture content levels below 0.20, 0.15, and 0.20 kg water per kg dry matter for untreated mango and samples treated with sucrose and isomaltulose, respectively. In all cases, equilibrium moisture content decreased with increasing temperature. Among the models tested, the Guggenheim-Anderson-de Boer (GAB) model provided the best fit to the experimental data (R² > 0.994, χ² ≤ 6.9 × 10^-4, RMSE ≤2.6 × 10^-2). The isosteric heat and entropy values suggested that moisture-solid interactions resembled those of pure water at moisture levels above 0.35 kg water per kg dry matter. Gibbs free energy values indicated a non-spontaneous sorption process for untreated mango, whereas sorption in treated samples was spontaneous.

The enthalpy-entropy compensation analysis confirmed that sorption processes in all mango samples were enthalpy-driven. Isomaltulose-treated mango exhibited the highest affinity for water, as evidenced by the most pronounced thermodynamic property values, highlighting its potential as a functional osmotic agent in fruit dehydration. © 2025 The Author(s). Journal of the Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.