Equilibrium Moisture Content of Rice

Abstract

Desorption equilibrium moisture content were determined by using the method of salt solutions (static method), for rough rice, brown rice and hull at 20, 30 and 40°C and at eight different relative humidities in the range of 11.3% to 85%. The short grain rough rice (cv. NIPPONBARE) used in this study was harvested at an average kernel moisture content of 30% d. b.. About 10g of rough rice, brown rice and about 3g of hull were put into glass patty dishes and then these sample holders were put in the same humidity control chamber. The weight change was measured each day using an electric balance until the change in weight reached 1mg/day. The moisture content of the samples at this stage was defined to be the equilibrium moisture content.
The Dubinin-Astakhov (D-A) equation which was derived based on Polanyi's potential theory was used to smooth the equilibrium moisture content data. The most suitable parameters of D-A equation were obtained for rough rice, brown rice and rice hull at 20, 30 and 40°C. These D-A equations were used to analyse the equilibrium moisture content data of rough rice, brown rice and hull. Using the data smoothed by this epuation, the equilibrium moisture content difference among rough rice, brown rice and hull was examined.