Performance evaluation of a centrifuge type grain cleaning machine and its effect on chemical and microbial quality of sorghum and millet grains

Abstract

Cleaning is an important unit operation in food processing. However, cleaning of some cereal grains including millet and sorghum prior to processing is tedious due to their small sizes. In this study, the cleaning efficiency of a locally fabricated centrifuge-type grain cleaning machine was tested and compared to the traditional method of cleaning. The centrifuge cleaning machine consists of an outer main frame which is stainless steel, cylindrical drum with a hundred percent opening discharge pipe on the lower side, an inner 250 μm perforated stainless steel cylindrical sieve, a motor-powered transmission stirrer unit with two bats placed adjacent at ninety degrees to each other. Color measurement of grain samples was done with a Lovibond Tintometer Colorimeter. The microbial load – enterobacteria, coliform, Escherichia coli, aerobic mesophiles, yeast and Staphylococcus aureus was analyzed using the AOAC (2012) methods. HPLC was used to quantify the aflatoxin levels - aflatoxins B1, aflatoxins B2, aflatoxins G1 and aflatoxins G2. The time and cost which initially took 8 h using two laborers at a fee of GHC100.00, was reduced to 3 h with just one laborer costing GHC50.00. Skinning damage to millet and sorghum caused by locally fabricated machine was determined to be 2.1% and 4.6% respectively. The results of the study showed that the cleaning machine could be adopted for small scale washing of millet and sorghum grains for foods such as fura