| Summary: | Adsorption isotherms provide insight into the thermodynamic properties governed by food storage conditions. Adsorption isotherms of purple corn of the Canteño variety were evaluated at 18, 25, and 30 °C, for the equilibrium relative humidity (ERH) range between 0.065 and 0.95. The equilibrium moisture (<i>X<sub>e</sub></i>) was determined by the continuous weight-change method. Seven mathematical models of isotherms were modeled, using the coefficient of determination R<sup>2</sup>, mean absolute error (MAE), and estimated standard error (ESE) as the convergence criterion. Thermodynamic parameters such as isosteric heat (<i>q<sub>st</sub></i>), Gibbs Free Energy (Δ<i>G</i>), differential entropy (Δ<i>S</i>), activation energy (<i>E<sub>a</sub></i>), and compliance with the isokinetic law were evaluated. It was observed that the adsorption isotherms presented cross-linking around 75% ERH and 17% <i>X<sub>e</sub></i>, suggesting adequate storage conditions at these values. The GAB and Halsey models reported better fit (R<sup>2</sup> > 97%, MAE < 10%, ESE < 0.014 and random residual dispersion). The reduction of <i>X<sub>e</sub></i> from 17 to 7%, increases <i>q<sub>st</sub></i>, from 7.7022 to 0.0165 kJ/g, while Δ<i>G</i> decreases considerably with the increase in <i>X<sub>e</sub></i>, presenting non-spontaneous endergonic behavior, and linear relationship with Δ<i>S</i>, evidencing compliance with the isokinetic theory, governed by <i>q<sub>st</sub></i>. <i>E<sub>a</sub></i> showed that more energy is required to remove water molecules from the upper layers bound to the monolayer, evaluated using <i>C<sub>GAB</sub></i>. The models predicted the storage conditions, and the thermodynamic parameters show the structural stability of the purple corn grains of the Canteño variety during storage.
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