Measuring and Modeling Grain Sorption Equilibria of Amaranth Grains

Abstract

Cereal Chem. 75(3):297-300Water activity (a w )of Amaranthus cruentus were measured at 35, 45, and 65°C at different moisture contents by means of an electronic water activity meter. Experimental curves were fitted to one three-parameter equation (GAB equation). The equilibrium values and temperature shifts were modeled with a three-parameter equation in the approximate a w range of 0.03-0.88. An analytical expression to calculate the isosteric heat of sorption and its moisture content dependence was used, and the results were compared with the isosteric heat calculated from the experimental equilibrium data by means of the Clausius-Clapeyron equation.

Sorption isotherms for amaranth grains

“…Experimental data of EMC-ERH (M e vs. a w ) of the species Amaranthus cruentus L. were taken from literature (Lema, Palumbo, Adaro, & Lara, 2001;Pollio, Tolaba, & Suárez, 1998;Tosi, Masciarelli, & Ciappini, 1994) for water sorption at 25, 30, 35, 40, 45, 50, 55, 65, 70 and 90°C in the range of water activity from 0.029 to 0.979. The data sets (Table 1) comprised experimental values of EMC-ERH that summarize 78 points for desorption, 53 for adsorption and 16 not discerned points that were considered for mean sorption.…”

Drying characteristics of amaranth grain

“…The equilibrium moisture contents of amaranth grain corresponding to the desorption branch of sorption isotherms at temperatures between 35 and 60°C were taken from the literature (Pollio, Tolaba, & Suarez, 1998). The desorption isotherm at 70°C, covering a water activity range between 0.10 and 0.90 was measured with Novasina Thermoconstanter Humidat TH2 meter, following the procedure described by Falabella, Aguerre, and Suarez (1992).…”

The drying of amaranth grain: mathematical modeling and simulation

“…The equilibrium moisture contents of amaranth grain corresponding to the desorption branch of sorption isotherms at temperatures between 40 and 60ºC were taken from the literature (Pollio et al, 1998). The desorption isotherm at 70ºC, covering a water activity range between 0.10 and 0.90, was measured with a Novasina Thermoconstanter Humidat TH2 meter, following the procedure described by Falabella et al, (1992).…”