Effect of operating parameters on milling quality and energy consumption of brown rice

The objective of this study was to evaluate the effect of operating parameters including milling weight (MW; 10, 95, 220, 345, 430 g), filling ratio (FR; 1, 1.4, 2, 2.6, 3) and milling duration (MD; 6, 30, 65, 100, 124 s) on head rice yield (HRY), whiteness index (WI) and specific energy consumption (Es). The experiments were conducted based on a vertical circulation mill employing a 5 level, 3 parameters CCD design and operating parameters were optimized using response surface methodology. During the processing, MW and MD had significant negative effects on HRY. On the contrary, they both had significant positive effects on WI. All the three parameters had a significant effect on Es Taking HRY, WI, Es as the evaluative index and degree of milling, temperature rise of milled rice as the restrictive index, the best combination of operating parameters was obtained, namely MW of 345 g, FR of 2.6 and MD of 30 s. The Pearson correlation coefficients between all the milling qualities were analyzed. Results showed that the temperature rise as an easy measurement index was highly correlated with the other qualities. The regression models between temperature rise and the other milling quality indices can assist in evaluating the quality of milled rice quickly and quantifiably.