Moisture Sorption Isotherm and Thermodynamic Characteristics of Palm Date Seeds Fiber Under Various Storage Conditions

ABSTRACT This study investigated the moisture sorption behavior of date seed fiber (DSF) using a dynamic vapor sorption (DVS) system at 25°C, 35°C, and 45°C over a water activity range of 0.1–0.9. In addition, thermodynamic properties of sorption behavior were investigated. The sorption isotherms exhibited a Type III profile, with rapid moisture uptake during adsorption and corresponding decreases during desorption, showing clear hysteresis. The optimal storage equilibrium moisture content at a maximum water activity of 0.6 (corresponding to 60% relative humidity) ranged from 0.078–0.081 kg/kg for adsorption and 0.098–0.101 kg/kg for desorption across the examined temperatures. Among nine tested models, The Peleg model gave the best results for adsorption ( R 2 ≈0.999), while the GAB model was superior for desorption and provided better physical interpretation. The net isosteric heat of sorption ranged from 42 to 43.8 kJ/mol and decreased with increasing moisture content, while differential entropy also decreased. Gibbs free energy values were positive for both adsorption and desorption, increasing as moisture content decreased, and followed an exponential trend. The combined analysis of equilibrium moisture content and thermodynamic parameters provides a comprehensive dataset on DSF moisture sorption under different temperature and humidity conditions. These findings provide valuable insights into food and pharmaceutical applications, supporting DSF use in fiber‐fortified products, beverages, and dietary fiber supplements, while offering predictive tools for storage and handling based on temperature and relative humidity.