MODELING WATER ADSORPTION ISOTHERMS OF PINHÃO (ARAUCARIA ANGUSTIFOLIA SEEDS) FLOUR AND THERMODYNAMIC ANALYSIS OF THE ADSORPTION PROCESS

摘要

The seeds of Araucaria angustifolia, commonly known as pinhão, arenwidely consumed in both Southern and Southeastern Brazil because of theirnhigh nutritious value. The literature on the technological aspects of this seednis still very scarce. Moisture adsorption isotherms of pinhão flour were determinednat 10, 20, 30 and 40C using the gravimetric method. Results show thatntemperature has little effect on the adsorption process and the Chirife modelnwas found to best represent the experimental data. The isosteric heat ofnsorption (differential enthalpy) was calculated by using the moisture adsorptionnisotherm and decreased as moisture content increased, becoming almostnconstant at 0.3 kg water/kg dry solids. The enthalpy–entropy compensationntheory was applied to adsorption isotherms and the isokinetic temperature fornpinhão flour was calculated by plotting the differential enthalpy versus differentialnentropy. It was found that the adsorption process investigated wasnenthalpy controlled.