Miller Magazine Issue 137 May 2021

63 COVER STORY MILLER / may 2021 wheat required, free from any form of infestations and good for milling. Also, all the quality parameters need to be check, in other to be able to adjust and set the param- eters to the required standard to achieve the required final product. • Efficient Cleaning system The wheat delivered to the mill is not pure but contains all kinds of foreign materials, sand, dust in the crease of the wheat, weed-seeds of all kind, as well as sometimes shrinkled wheat. These impurities may vary between 1-3% .or 3-10% according to the country of origin. A poor cleaning system can drastically affect quality. If inorgan- ic materials like Iron, dust, stones and other impurities escape to the mill, it will not only impair the quality of the product but cause harm for human health when con- sumed, damages of machines' components, and could cause dust explosion in the plant. Therefore, the raw grains must be properly prepared by passing through different cleaning machines to re- move the impurities before conditioning and tempering of the wheat. The cleaning machines make use of the different principle of separation such as; Separation Principle Machines • Size Drum sieve, Separator • Terminal air velocity Aspiration channels • Magnetic reaction Magnet separator • Density De-stoner, Combinator • Length Indented separator • Shape Spiral separator • Reflection of visible light spectrum Optical sorter This is needed to separate particles and impurities that differ from wheat and must be carefully removed. There is a true saying in milling: “A well-cleaned wheat is half grinded!. The cleaning machine must work continuously at high efficiency, without a repetition of that operation. For example, the insufficient performance of one of the cleaning machine like the aspiration machine will lead to: • A significantly higher presence of mineral dust parti- cles in the mass of the wheat grain and on the surface of wheat kernels. This dust presents a high risk of moving to flour mass, generating color problems, ash, etc. • Unseparated foreign bodies in the cleaning section, because of higher friability than endosperm’s, may gen- erate particles that give the same problems of color, i.e. ash, and also affects extraction by inflating the bran per- centage. MILLING YIELD / EXTRACTION The purpose of a milling activity is the transformation of a mass of milling grain into finished products. The pro-