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A systematic analysis of roll speed combinations and resulting roll differentials
H. DOGAN (1), Y. Chen (1) (1) Kansas State University, Manhattan, KS, U.S.A..

The first break is the most important of the gradual reduction systems in flour milling. Size reduction process is affected by operational parameters of the break rolls as well as the physical properties of the wheat kernels. Roll differential, the difference between the speed of the fast and the slow rolls, is known to affect the granulation. Although there are several studies on the effect of roll differential, the effect of roll speed combinations resulting same differential has not been well studied. The objective of this work was to study the breakage behavior of wheat kernels at constant differentials of varying roll speeds. Experiments were carried out at (1) constant slow roll speed of 144 rpm and varying differentials (i.e. 360:144, 288:144, 216:144), (2) constant fast roll speed of 360 rpm and varying differentials (360:144, 360:180, 360:240), (3) constant differential of 1.5 at varying roll speed combinations (360:240, 288:192, 216:144), (4) constant differential of 2.0 at varying roll  combinations (360:180, 288:144, 216:108), and (5) constant differential of 2.5 at varying roll speed combinations (360:144, 250:102, 200:80). E?ectiveness of these first break operations were tested for break release, ?our yield, particle size distribution, as well as ash and protein content. Both tests 1and 2created coarser particle size distributions at low differential of 1.5, while keeping the slow roll speed constant resulted in a wider distribution gap compared to keeping high roll speed constant. In tests 3-5, faster roll speed combinations at constant roll differentials resulted in production of higher percentage of fine particles.