Histeresis de sorción de agua del maiz cusco (Zea mays L. indurata) expandido por explosión

Water adsorption and desorption isotherms of the puffed and unpuffed corn were determined at different temperatures, using a gravimetric method for isotherm measurement with adjustable water vapor pressure, exhibiting between the curves is called hysteresis. The adsorption isotherm curve is obtained from the dried product increasing the water vapor pressure around the sample while the desorption isotherm is taken from the humid one decreasing the vapor pressure in equilibrium. These curves do not match each other in practice and this divergence between the curves is called hysteresis. By comparing the water desorption and adsorption curves of raw and puffed corn, one observes the hysteresis phenomenum in most cases. The expansion process changes the adsorption and desorption characteristic at the tested temperatures. The puffed corn becomes more hygroscopie, this effect being stronger at higher temperatures. The equilibrium humidity contents are larger in the puffed corn. Monolayer moisture contents, calculated by means of the BET equation, show values higher for the puffed corn than those of the raw corn. Thermodynamical considerations are made, as well as the experimental data fitting according to the Chung-Pfost equations.