Separation of maize particles from alcohol extracts with minimal losses

Low-cost extraction of maize protein using ethanol at the front end of a dry grind ethanol plant has been discussed in recent articles. Thorough recovery of (alcoholic) extract from the extracted maize is essential to make the process economical and to prevent the ethanol from interfering with liquefaction enzymes or fermentation organisms where the solid residues are to be subsequently reduced to glucose and finally fermented to ethanol. Because the particles will be converted in water it is unnecessary to dry them, if a (miscible) liquid/liquid miscible displacement method can be used. Therefore, three methods of displacing extract liquid from the extracted corn particles were tried using (1) packed bed displacement, (2) centrifugation with rinsing, and (3) gravitational settling into water. Displacing extract (liquid) from a stationary bed of milled corn extract was too slow to be practical. This finding should discourage the use of similar techniques based on stationary layers of extracted corn. Continuous centrifugation, with rinsing by fresh ethanol solution, was effective at recovering protein in the extract with rinse rates comparable to extract feed rates. Settling the extracted corn into water appears to be the most feasible method of separation, requiring low extract dilution and inexpensive equipment. (C) 2002 Elsevier Science B.V. All rights reserved.