Adsorption isotherms and thermodynamic properties in tarwi (Lupinus mutabilis) flour

Briceño-Sevillano S.M.; Marceliano-Sánchez L.; Vegas-Niño R.M. · Revista U.D.C.A Actualidad and Divulgacion Cientifica (2025) · DOI: 10.31910/rudca.v28.n1.2025.2540

Resumen

In Peru, Andean lupin (Lupinus mutabilis) is marketed primarily as a whole grain, its conversion into flour is limited and almost nonexistent as defatted or hydrolyzed flour. Although it is rich in proteins and lipids, its market value in Peru remains low. Sorption isotherms are fundamental tools for studying processes such as drying, mixing, permeability, and packaging, allowing for the prediction of the physicochemical stability of foods. In this study, the sorption isotherms of tarwi flours were evaluated gravimetrically under three conditions: delupinized (1), defatted (2), and hydrolyzed (3), along with their thermodynamic properties. The samples were exposed to water activities (aw) ranging from 0.1 to 0.9 and 20, 30, and 40 °C temperatures. The data obtained were fitted using the GAB model (Guggenheim, Anderson, and de Boer). Parameters such as isosteric heat (Qst), adsorption surface area (AS), sorption entropy (ΔS), and Gibbs free energy (ΔG) were analyzed. It was observed that as aw increased, so did the equilibrium humidity (Xm), while for a constant aw, increasing temperature reduced Xm. The isotherms displayed a type II sigmoidal shape. The highest Qst values were recorded in the hydrolyzed flour. The monolayer and surface area values were greater at 20 °C in all cases; in addition, flour in condition 2 had the highest values with 0.087 g H2O/g d.m. and 308.86 m2/g d.m., respectively, while ΔG indicated spontaneity in the processes for conditions 2 and 3.

Instituciones: Universidad Nacional de Trujillo