Adsorption isotherms of barley at low and high temperatures

Thirty-three measurements of adsorption equilibrium moisture content (EMC) for barley were experimentally determined using a constant environment chamber for various combinations of air relative humidity (48.2-88.6%) and temperature (5.7-46.3 degreesC). A thin-layer technique was used to obtain uniform re-wetting. Each test required from 4-6 days to attain dynamic equilibrium moisture contain. Four commonly used: three-parameter EMC/ERH (equilibrium relative humidity) equations, modified Henderson, modified Chung-Pfost, modified Oswin and modified Halsey, were evaluated for their ability to fit the experimental EMC/ ERH data using non-linear regression techniques. Comparisons were made on the basis of standard error of estimate (SEE), residual sum of squares (RSS) and residual plots. The comparison showed that the modified Chung-Pfost equation was the most appropriate equation for modeling the EMC/ERH adsorption isotherms of barley. The coefficients both for EMC as a function of ERH and temperature, and ERH as function of EMC and temperature are given. The adsorption EMC data obtained in this work agree with previous published data. The equations were fitted to EMC/ERH data obtained at a wide range of temperatures and therefore will be helpful for future work on drying, re-wetting and storage of barley. (C) 2004 Published by Elsevier Ltd.