Thermodynamic analysis of the sorption isotherms of pure and blended carbohydrate polymers

The adsorption isotherms of gum Arabic (GA), mesquite gum (MG), and maltodextrin DE 10 (MD), and a blend of the three gums (17%GA–66%MG–17%MD) were determined at 25, 35, and 40 °C. All isotherms were fitted using the GAB model and the thermodynamic properties (enthalpies and entropies, differential and integral) were estimated by the Clausius–Clapeyron method. The minimum integral entropy was considered as the point of maximum stability where strong bonds between the adsorbate and adsorbent occurred, and water is less available and likely to participate in spoilage reactions. The point of maximum stability was found between 12.24 and 14.68 kg H2O/100 kg d.s. (corresponding to water activity, aw, of 0.32–0.57) for GA, 12.12–14.27 kg H2O/100 kg d.s. (aw = 0.33–0.55) for MG, and 11.37–13.84 kg H2O/100 kg d.s. (aw = 0.28–0.55) for the biopolymer blend, in the temperature range studied.