THERMODYNAMIC PROPERTIES OF THE WATER ADSORPTION PROCESS IN BARU FLOURS

ABSTRACT

Baru almonds and their byproducts have gained popularity in the population diet because of their high nutritional values. Despite this, there is limited information on how to store their flours properly, particularly their whole and partially defatted flours. Thus, this study aimed to use the Guggenheim–Anderson–de Boer (GAB) model to determine the thermodynamic properties of enthalpy, entropy, and Gibbs’s free energy variation, as well as the spreading pressure, all of which are inherent to the moisture adsorption process in baru flours. The oil content, ash content, moisture content, pH, and wettability of the baru flour samples were characterized. The adsorption isotherms were determined using the static gravimetric method at temperatures of 298.15, 303.15, and 308.15 K and adjusted to the GAB model. The differential enthalpy variation was positive and decreased as the moisture content in the flours increased, whereas the differential entropy variation exhibited an opposite trend. The isokinetic theory was validated, as the process was driven by entropy. The spreading pressure increased as water activity increased.

Dipteryx alata Vogel; GAB model; differential enthalpy; differential entropy; isokinetic theory