Bulgur milling using roller, double disc and vertical disc mills

Abstract

In the present study, roller, double disc and vertical disc mills were used to determine their effects on the quality of bulgur (surface characteristics, shape, dimension ( x, y, z), particle volume ( V), bulk density, one-thousand particles weight and size). Eighteen kilowatt motor was used and gap width was fixed at 2.50 mm for the mills. The roller mill had the highest milling yield (99.19%). Smooth and glassy particle surface was obtained due to the sharp-to-sharp operational principle of the roller mill (cutting effect). The quantity of coarse (/2.20) bulgur particle was higher than that of middle (2.20/2.00) and fine (2.00/0.50) bulgur particles. One-thousand particles weight and bulk density were found as 6.93 g and 63.76 g/100 mL, respectively. However, uniform particle shape was not obtained from the roller mill. It could be due to the irregular cutting of the particles between teeth of the roller mill. The coarse, middle and fine bulgur were obtained using the double disc mill at the percentage of 22.30, 34.60 and 37.94, respectively. The double disc mill caused low surface quality in contrast to obtained ovoid or elliptical shape. Moreover, its yield was 94.84%. Vertical milling position of the vertical disc mill decreased the retention time of bulgur particles in the milling zone therefore, ellipticity (ovoid) of bulgur particles was lower than that of the double disc mills. The milling yield of vertical disc mill was 97.60%, which was higher than the double disc mill (94.84%).