Study of Adsorption and Desorption Equilibrium Relationships for Yellow Dent, White, and Waxy Corn Types Using the Modified Chung-Pfost Equation

Abstract

Three different corn types (yellow dent, waxy, and white) harvested in the fall of 2003 were used to run a set of desorption and adsorption EMC/ERH experiments. The range of temperature and moisture content (MC) were designed to cover the typical operating conditions for natural air / low-temperature in-bin drying systems in the Midwest during the fall (0°C to 25°C and 12% to 20% for temperature and MC, respectively). Standard deviations of the experimental data ranged from 0.00°C to 0.58°C, 0.00% to 0.52% for EMC values, and 0.01% to 4.36% for ERH values. Non-linear regression analysis was used to determine the best adsorption and desorption parameters for the modified Chung-Pfost equation for each corn type. A second adsorption and desorption EMC/ERH experiment was carried out with samples of yellow dent and white corn harvested during the 2004 drying season. The modified Chung-Pfost equation using the 2003 set of parameters was validated with the 2004 EMC/ERH data. The MRD and SE for the three corn types ranged from 1.9 to 2.6 and 1.6 to 1.9 compared to 4.3 and 5.0, respectively, reported for the ASAE Standard data. The main conclusions of this study were that the different corn types investigated had different EMC/ERH relationships, the adsorption and desorption relationships were different for each corn type, and the prediction of EMC/ERH values during desorption using the current ASAE Standard set of parameters available only for yellow corn was substantially different compared to the yellow dent, white, and waxy corn EMC/ERH data reported in this research.