RELATING DRYING RATE CONSTANT TO HEAD RICE YIELD REDUCTION OF LONG-GRAIN RICE

Abstract

Long-grain rough rice was dried at various rates and durations and milled to determine head rice yield. The drying data were described by a Newton equation, and the resultant head rice yield reduction data were described by an empirical rate equation. Effects of drying condition, variety, harvest moisture content, and storage time prior to drying were investigated, but only the first two of those variables significantly affected the drying rate constant, and the first three of those variables significantly affected the head rice yield reduction. Head rice yield reduction was directly related to the drying rate constant. At a given drying rate constant, head rice yield reduction increased with drying duration. An empirical model was developed to predict the head rice yield reduction as a function of drying rate constant and drying duration. This model may lead to optimal control of rice dryers in terms of minimizing head rice yield reduction during the drying process.