Stationary rice drying: Influence of initial moisture contents and impurities in the mass grains on the physicochemical and morphological rice quality

Abstract

The initial moisture contents and impurities in the grain mass can interfere with the drying operation in a stationary dryer. Thus, the objective of this study was to evaluate the effect of drying air movement in the rice mass as a function of initial moisture contents (19, 18, 17, and 16% w.b.) and impurities (1.5, 2.5, 2.0, and 3.0%) on the physicochemical properties and morphological rice quality. The moisture and impurity contents provided alterations in the movement and distribution of the drying air in the upper layers of the stationary dryers. Consequently, the physicochemical properties and morphological quality of rice were altered. In addition, the reduction in the starch and fat contents was correlated to higher percentages of crude protein, mainly upper grain layers. Thus, the rice mass at moisture content of 17% (w.b.) and impurity at 2.5% allowed major uniformity and greater drying versatility in the stationary dryer for rice quality. Practical applications The rice drying in the stationary dryer is an excellent option to reduce drying and storage infrastructure and achieve satisfactory grain quality, as long as there is an adequate control and management of the batches of grain received in terms of moisture uniformity and impurity contents. For proper rice management in the stationary dryer, it is recommended to pre-cleaning the grain mass to 2% of impurities, while the initial grain moisture content for drying must be below 18% (w.b.). The standardization of batches in terms of initial moisture content and impurities allows for an adequate flow and distribution of air in the grain mass to obtain efficiency in drying at low temperatures and maintaining grain quality. From a commercial point of view, the grains can remain in the drying process and stored in silo-dryers for the harvest period until the time they can be sold at better market prices.