Effects of variety and harvest moisture content on equilibrium moisture contents of rice

Equilibrium moisture contents (EMC) of two long-grain rice varieties (Kaybonnet and Cypress) and one medium-grain variety (Bengal) were measured at temperatures of 4, 21, and 38 degrees C with relative humidities (RHs) ranging from 11 to 96%. In addition to temperature and RH, variety was a significant factor affecting rice EMC. Harvest moisture content (HMC) and harvest location did nor significantly affect the EMC of rough rice. Rice harvested at a lower moisture content (MC) had lower EMC values than rice harvested at a higher MC when equilibrated to high RHs; however these differences were primarily attributed to hysteresis effects. Art EMC model including temperature, RH, and variety was developed. At most RHs, the EMCs of Bengal, Kaybonnet, and Cypress rough rice were approximately 0.2 to 0.8 percentage points higher than that calculated from the Chung EMC equation. New coefficients of the Chung equation for rough and milled rice are provided.