Optimization of Rice Coating Process Using Response Surface Methodology

Abstract

Abstract-The objectives of this study were to optimize the operating condition of the top-spray fluidized bed coating process on rice and to investigate the effects of coating factors on physical properties of coated rice. The coating factors tested in this work consisted of inlet temperatures (60-80C), spraying times (5-15 min) and feed rates (6-10 ml/min). Maltodextrin solution (20 Brix) mixed with red food color was used as coating solution. Response surface methodology was used to describe the effects of all factors with respect to responses including %fissure, %head rice yield (HRY) and chroma. Full factorial design was used for the experimental design with the use of three levels. In addition, the subsequent experimental data was fitted to quadratic regression models to describe the relationship between all factors and each response. The surface plots obtained from the experimental results revealed that all factors reasonably affected the physical properties of the coated rice. The increasing inlet temperature resulted in higher percentage of fissure. The %HRY and chroma was not affected by the inlet temperature. When the spraying time increased, it was found that chroma was higher, while %fissure and %HRY were not affected by this parameter. Furthermore, the coating solution feed rate led to a decrease in %fissure and %HRY, while the chroma increased. With the respect to the regression of determination (R 2 ), the quadratic models were found to be the suitable model for each response with high R 2 ranging from 0.83 to 0.93. Based on maximized %HRY and chroma, and minimized %fissure, the maximum desirability of operating condition was 0.51 at feed rate of 8.80 ml/min, spraying time of 10.23 min and inlet air temperature of 60C.