Milling Journal - Q4 2008 - (Page 16) As a rule of thumb, 12 meters of roll length and one eight-section plansifter, plus intensive detachers, drum detachers, and bran finishers enabled a milling capacity of 100 tons of wheat per 24 hours. Roller mills velocity increased to 650 rpm. The design of roller mills was changed from having rolls in a diagonal position to a horizontal position. Roll construction changed from casting body to welded body, with the roll pack having self-contained forces. This boosted the milling capacity of roller mills. However, the quality of the flour produced by modern short mills is much lower than in the 1980s. The reason for this is the high intensity of the milling, which damages the gluten and produces too much starch damage. As a result, the bakers must use more additives than in the 1980s to get the same quality of baked goods. Double-High Milling As mentioned earlier, many flour mills introduced double-high roller mills, in order to save space, pneumatics piping, energy, sifting area, etc. Some mills at the start of the 1990s were designed utilizing only double-high roller mills. Double high roller mills can be used in some places in the mill, but also have some disadvantages: 1. The lower rolls get their feed from the upper rolls. In the upper rolls, some intermediate materials are produced, which normally have to be sifted and sent to the right roller mills. Instead, they are sent to the lower rolls, which are not designed to mill them. For example, if the upper rolls are first break and the lower rolls are second break, products like coarse and fine semolina are milled in the lower rolls, which are designed for milling second break and flour, which is produced in the upper rolls, is fed to the lower rolls instead of being sent to the collecting flour conveyor. 2. Because the feed from the upper rolls is entering the lower rolls without any cooling, temperatures in the outlet of the lower rolls are very high, which damages flour quality and causes condensation problems in the milling equipment. 3. Compared to a single-high roller mill with traditional intermediate sifting, double-high roller mills produce approximately 30% less flour. The short milling system needs about 10% more electric power than the conventional mills of the 1980s, and maintenance expenses are higher because of the intensive wear. Therefore, there is a tendency today to design new mills again with longer specific roll length (about 14 mm/100 kg/ 24 hours). Despite that, I think that the length of 1416 mm/100 kg/24 hours is much better for the milling systems and for product quality. Current Systems The Shalom Flour Mill went through all the developments in milling systems as described from the early 1930s until today. We have three milling systems. In mill No. 1, we produce flour like we did in the 1980s, on a mill with a specific length of 17 mm/100 kg/24 hours. In mill No. 2, built in 2000 to a short-mill design (12mm/100kg/24 hours) using a double-high roller mill, we mill only soft wheat flour, which requires a shorter roll length. Sometimes we mill bread flour on mill No. 2, but it is only for baking products that do not need high-quality flour. We also have taken into account the fact that wheat quality worldwide today is lower than years ago for economical reasons. Short roll length results in lower flour quality and flour needs higher levels of chemical additives, going against today’s trend toward healthier food products. 16 Fourth Quarter 2008 Response No. 161 MILLING JOURNAL http://www.hiroller.com http://www.hiroller.com
For optimal viewing of this digital publication, please enable JavaScript and then refresh the page. If you would like to try to load the digital publication without using Flash Player detection, please click here.