Desorption isotherms and isosteric heat of baru almond flour

Abstract

Baru almond (Dipteryx alata Vogel) is a nutritional and tasty product; the flour of this product is used in culinary recipes. In the processing of the almond, the chemical composition and structure of the product changes, influencing the hygroscopicity of the material. Thus, the objective was to determine the behavior of the water activity of baru almond flour at different temperatures, adjusting the best mathematical model to estimate the isotherms, as well as to determine the isosteric heat of desorption. The almonds were dried for moisture contents in the range of 5.4 to 3.3 ± 0.03% dry basis (d.b.), then the almonds were processed in an industrial blender to obtain the flours. To determine the desorption isotherms, the static-indirect method was used, in which the water activity was obtained at temperatures of 10, 20, 30, and 40 ºC, using the Hygropalm Model Aw1 equipment. The hygroscopic equilibrium moisture content of baru almond flour was directly proportional to water activity and decreased with increasing temperature, to the same water activity value. The Chung-Pfost model was the one that best represented the product’s isotherms. The integral isosteric heat of desorption of baru almond flour ranged from 2590.69 to 2519.52 for the moisture content range of 3.24 to 5.43% d.b.