The effect of rice milling time and feed rate on head rice yield and color properties

Abstract

This study has been carried out to evaluate the head rice yield, kernel broken and the chance of color depend on milling time and feed rate. In this study, threshed rice kernels by combine-harvester at different cylinder speeds, rice harvesting season in 2018, were used for experiment test. According to results, head rice yield decreased slightly as the cylinder speed increased, with yields varying between 71.40 % and 70.28 %. Processing time was found to have a highly significant effect (p<0.01) on the quantities of unbroken kernel, broken kernel, bran, yield and husk. The highest rate of broken kernel was obtained at a processing time of 25 seconds, and the lowest values were obtained at a processing time of 10 seconds. With a processing time of 10 seconds, the quantities of unbroken kernel, broken kernel, bran, yield and husk were 70.74, 3.260, 0.810, 74.37 and 24.82 %, respectively. When the processing time was 25 seconds, the quantity of broken kernel decreased from 70.74 percent to 62.86 percent, and yield decreased from 74.37 % to 67.58 %. The broken kernel ratio increased from 3.26 percent to 4.633 percent and bran ratio increased from 0.8642 percent to 1.822 percent. Husk ratio, on the other hand, increased from 24.82 % to 30.60 %. In other words, as the processing time increased, so did the bran ratio and husk ratio. The highest whiteness value of 70.92 was obtained at a processing time of 25 seconds; while the lowest whiteness value of 63.81 was obtained at a processing time of 10 seconds. There were declines in a and b values as processing time increased, although the differences were not statistically significant. The highest a and b values were obtained at a processing time of 10 seconds, with -0.690 and 15.01, respectively. In conclusion, when processing paddy to rice, processing time needs to be increased to obtain a whiter rice; to have fewer broken kernels and a higher head rice yield, on the other hand, the processing time needs to be short.