Quantifying of the relationship between novel intermittent drying variables and some quality properties of parboiled rice using response surface methodology

Abstract

In this research, the effects of intermittent drying variables on some quality properties of parboiled rice were investigated, then a mathematical model was applied to predict the value of quality features non-destructively using response surface methodology (RSM). The intermittent drying variables consisted of hot air temperature (40, 50 and 60 °C), radiation intensity (0.21, 0.31 and 0.41 W/cm 2) and microwave power (100, 200 and 300 W). The intermittent drying was performed at two stages with a tempering time between drying steps using a hybrid drying of hot air-infrared radiation and microwave drying at the first stage and second stage, respectively. According to RSM results, the effect of drying variables on the quality properties of parboiled rice were significant (p < 0.01). Also, the best mathematical model for prediction of quality properties of samples was the quadratic equation (R 2 = 0.96-0.98). The HRY (61.8-73.2%), hardness (118.63-215.27 N) and color value (17.28-19.22) increased, while the lightness (64.17-59.51) decreased during drying. RSM can be able to predict the optimization parameters for the best quality properties (i.e., HRY = 72.42%, lightness = 59.47, color value = 19.25 and hardness = 213.91 N) based on temperature of 60 °C, radiation of 0.41 W/cm 2 and power of 300 W.