Effects of environmental changes on milling quality of rough rice

Abstract

Rough rice may fissure if it is exposed to an adverse environment for a certain period of time. The fissured rough rice will then cause a reduced head rice yield after milling. A Hart Uni-Flow Cylinder Tester was used to sort milled rice into three fractions: head rice, large brokens and small brokens. The performance of the separating unit at different combinations of its four operating variables-drum rotating speed, recovery spout position, operating time and indent size-were investigated. The combinations which gave the best separating results were chosen for determining the milling quality of rice samples which had been subjected to environmental changes. Samples of two rice varities, Labelle and Brazos, initially conditioned to two levels of moisture content, 9.35 (low) and 11.90 (high) percent (d.b.), were exposed for four days to eight different temperature and humidity combinations. The moisture adsorbed by each sample was recorded at 24-hour intervals for each treatment (there were a total of 32 treatments). Samples were then reconditioned to the room ambient environment for three weeks. All samples were shelled and milled, and the milled samples were sorted into three fractions: head rice, large brokens, and small brokens by the Hart Uni-Flow Cylinder Tester using the established procedure. ...