Effect of hammer mill retention screen size on fiber separation from corn flour using the Elusieve process

Corn is widely used as animal feed as well as for fuel ethanol production. Fiber present in corn is not digested well by non-ruminants such as chicken and swine. Also, this fiber does not participate in conversion of starch to ethanol. Fiber separation from ground corn flour using the Elusieve process, a combination of sieving and elutriation (air classification) results in high starch animal feed, and in increased ethanol productivity. The objective of this study was to understand the effect of retention screen size in the hammer mill on fiber separation from corn flour using the Elusieve process. Four different retention screen opening sizes were studied; 1.4 mm (3.5/64”), 2.0 mm (5/64”), 2.8 mm (7/64”) and 3.2 mm (8/64”). Ground corn flour was sieved into size fractions and the size fractions were subjected to air classification. As the retention screen size increased, fiber separation improved, and the difference in starch content between enhanced flour and original flour increased. The highest starch content of 64.1-65.2% was in the enhanced flour from Elusieve processing of corn flour obtained by using 3.2 mm (8/64”) retention screen in the hammer mill, while the starch content of the original corn flour was 62.5%. It is expected that at some threshold retention screen size, the fiber separation using the Elusieve process would be deteriorated. This threshold retention screen size was not reached in this study.