Moisture Sorption Isotherms of Vetch Seeds at Four Temperatures

The equilibrium moisture contents were determined for vetch seeds using the gravimetric static method at 5, 20, 40 and 60°C over a range of relative humidities from 0·110 to 0·877. The sorption capacity of the seeds decreased with an increase in temperature at constant relative humidity. The hysteresis effect was lower at higher temperatures. Five equations were applied for analysing the experimental data: modified Chung-Pfost, modified Halsey, modified Oswin, modified Henderson, and Guggenheim-Anderson-de Boer (GAB) equations. The modified Oswin model was the most suitable for describing the relationships between equilibrium moisture content, relative humidity and temperature. Vetch seeds maintained a monolayer moisture content when stored at a relative humidity in the range 0·17-0·18 regardless of the temperature.