Comparison of five three-parameter equations for the description of moisture sorption data of mustard seeds

Equilibrium moisture contents (EMC) of seeds of yellow, brown, and oriental mustards were determined at five different temperatures (2, 10, 25, 40, and 55°C) by equilibrating about 10-g samples at relative humidities in the range of 11–96%, obtained using saturated salt solutions. the EMCs of all three types of mustard decreased with an increase in temperature at constant relative humidity. At most temperatures and at the relative humidities tested, oriental mustard seeds had the lowest, yellow mustard the highest, and brown mustard intermediate EMC values. Differences in the moisture adsorption characteristics of the three mustards were attributed to differences in mucilaginous material, oil and protein contents of the seed. the modified GAB equation together with four other commonly used three-parameter equations (modified Henderson, Chung-Pfost, Halsey, and Oswin equations) were evaluated for their ability to fit the experimental data for the three types of mustard. the modified GAB equation gave the best fit to the experimental data and the modified Oswin equation was the second best model for describing the EMC data of mustard seeds. the predicted safe storage moisture contents of oriental, brown and yellow mustard seeds at 25°C were 10.0, 10.6 and 10.7% (db), respectively.