Miller Magazine Issue: 113 May 2019

52 COVER STORY MAY 2019 quality of the grain used as a basis must be stated in the analysis, mostly foreign matter and moisture content. The break system is where you open the kernel and scratch the endosperm out of the bran. It is done in two stages. The primary break opens the kernel and remo- ves the bulk of the endosperm. The secondary break removes the remaining endosperm from the bran. The breaking rollers are corrugated, and they rotate at different speeds. This imparts a shearing action on the grain, that scraps the endosperm. The corrugations are very few in the initial stages and increase in density as the process goes through the next stages. Ideally, this process would only produce clean chunks of endos- perm on one side and big flakes of bran on the other. The grading system is composed of redust sifters, where the products of the breaking rolls are classified according to size and the level of bran attached. The sizing rolls reduce and size the endosperm frag- ments so to feed the midds. It is crucial to minimize the bran that goes into the midds, as the bran is where you get the higher ash content. The purifier system is where the fine particles of bran are separated from the fine particles of endos- perm. The coarse particles of endosperm are also se- parated here. This is best achieved with purifiers, but in soft wheat milling, this process can be performed with rolls and sifters. By compressing particles, the endosperm is broken and the bran is flattened, so the sifters can classify it. Still, technically this is considered purifying. The midds section is where actual flour is made. Smo- oth or finely corrugated rolls break down the endos- perm particles. The low-grade system is where the low-quality flour rejected from the midds section gets a second chance. Using high efficiency sifters, these by-products are cle- aned again to get as much flour as possible from them. For each variety of wheat, you will need a different allocation of machinery. The calculations are as follows: Roll surface = (mm roll length) / (100 kg wheat pro- cessed in 24 hours) Sifter surface = (square meter sifter area) / (100 kg wheat processed in 24 hours) Purifier surface = (mm sifter width) / (100 kg wheat processed in 24 hours) Roll length, sifter surface and purifier surface have to be specified next to each equipment symbol in the flow sheet. The information in the flow sheet tells the miller the equipment capacity and the product allocation for each one, according to the raw material fed and the final products required. By closely analyzing it, the miller is able to make changes to the flow of material and adjust the quality accordingly. Designing your flow sheets is a formidable work, that will pay off immensely in the near future. References: Khan, K. and Shewry, P. (2009). Wheat, Chemistry and Technology, 4th Edition. AACC International Inc. Fowler, M. (2013). Flow Sheet Analysis. Milling Jour- nal. Pp 50 – 53. Posner, E. Wheat. In: Kulp, K. and Ponte, J. ed., Handbook of Cereal Science and Technology, 2nd Editi- on. Marcel Dekker Inc.