Relative humidity effects on the development of fissures in rice

Rice grains may develop fissures due to internal stresses when subjected to moisture-adsorbing environments. Rough, brown, and milled rice grains were conditioned to three equilibrium relative humidities (erh) of 46, 62, and 80%, before being exposed to high relative humidity (rh) environments of 65, 86, and 100% for different periods. Grains equilibrated to 46 and 62% erh fissured when exposed to either 86 or 100% rh. For rice grains at 46% erh, the cumulative percentage of fissured grains (CPFG) increased as the exposure humidity increased, with all of the milled rice fissuring at 100% exposure humidity. The CPFG decreased sharply as the initial moisture level increased, with no grains developing fissures when rough rice at 80% erh was exposed to 100% rh. The cumulative number of fissures (CNF) in rice grains increased with exposure rh and exposure time. The regression equations to describe CPFG and CNF related to erh, exposure rh, and time were developed from the SAS Statistical program