Miller Magazine Issue: 119 November 2019

75 ARTICLE MILLER / NOVEMBER 2019 of the crease are submerged within the kernel itself. All of these wheat kernel structure factors make separating the endosperm of wheat kernel not easy, which means that to do that, the grain has to be break opened through mechanical means (Bunn, 2000; Campbell, 2007). Millers make their efforts to have three major objectives, which are the optimum extraction rate with the maximum quality of finished products and the capacity of the mill. Their efforts for these objectives are aimed to have the optimum economic balance of these objectives (Posner and Hibbs, 2005; Campbell, 2007). Miller to achieve his aim has to practice efficient milling techniques and to optimize the streams of every machine in the mill (Bunn, 2000). So intermediate streams are continuously moni- tored for quantity (distribution table), quality (ash curve), and granulation (break release and granulation curve) and this data is used for adjustment by the miller (Posner and Hibbs, 2005). These techniques will be discussed in a series of ar- ticles. In this article break release technique will be dis- cussed. THE BREAK SYSTEM Wheat milling process can be divided into three main system: break, sizing, and reduction. To obtain a high ex- traction rate of flour with low ash content, the miller’s first objective in the break system have to be to break open the wheat kernel and release as much as possible clean endosperm particles in large size of sizing and middlings, leaving the bran in large particles and minimum amount of flour (Bunn, 2000; Campbell, 2007; Serna-Saldivar, 2010). The objective of the sizing and re- duction systems is to reduce sizing and middlings into flour (Serna-Sal- divar, 2010). The sizing system grades the endosperm, producing a narrower particle-size range, thus optimizing the performance of the re- duction system (Miskelly and Suter, 2010). There are generally 4–6 break roll passages (1BK, 2BK, 3BK, etc.) which have successively finer spiral flutes. Between each of the break operations, the stock is sieved in a plansifter separating flour from bran and larger endosperm particles (Mi- skelly and Suter, 2010; Serna-Sal- divar, 2010). The break system products are bran, siz- ing, middling and flour. Sizing is the endosperm particles which have particle size in the range 210-500 μm. Mid- dlings is the endosperm particles which passed from 210 μm and bigger than 150 μm. The amount of flour must be minimized and the particles are smaller than 150 μm sieve (Serna-Saldivar, 2010). Bran must be in flakes shape and free from adhering endosperm. The size of bran particles is over 500 μm. Bran finishers remove any remaining flour from the coarse bran after the break sys- tem (Miskelly and Suter, 2010). 1st and 2nd break rolls are to release the maximum amount of puro sizing and middlings in the correct quan- tities with regards to mill designed balance, whilst keep- ing the bran skins course, and with the minimum pro- duction of the bran fine particles. 3rd and 4th break rolls are to clean up the resulting break stocks and to recover any remaining endosperm still adhering to the bran while taking care not to create fine bran particles (Bunn, 2000). Primary breaks (first, second and third) are the most heavily loaded in the mill and establish the load to purifi- ers, sizing rolls, and the reduction system. The second- ary breaks (fourth and fifth) are not responsible for the intensive contribution to flour yield. However, recovery of fine middlings to the tail end of the reduction systems is critical for acceptable flour yields (Posner and Hibbs, 2005). The amounts of fine products especially bran which are produced in the break system have to be minimized. Because the difficulties of separating flour from fine bran if produced in the early stages of break system the whole