Minimizing entrainment of extract liquid by settling maize particles

An ethanol soluble protein (zein) can be extracted from maize meal. Development of a cost effective protein recovery process requires that the extracted maize particles be separated from the extract. We have previously shown that the particles can be settled into a water layer, through a stagnant interface, with low dilution of the protein-containing extract liquid. In this article, we describe testing done to develop settling tank base inclinations that enable the settled particles to be pumped from the tank as rapidly as they settle to the water layer. Ethanol extracts were pumped to one side of an ethanol solution layer floating on a water layer. The ethanol solution was kept at a constant height by pumping from a port opposite and higher than the inlet port and by maintenance of a constant water layer height. The solid particles in the extract settled into the water. Water was continuously pumped to and from the tank. Laminar water flow alone did not remove the particles at the lowest sustainable extract feed rate. Particles could be pumped out of the tank at rates equal to practical rates of extract feed when they settled on a base inclined 35degrees to the horizontal. The rate of extract liquid entrainment by the settling particles was determined from measurements of the mass of the solids settled into the water layer and the density of the dilute ethanol solution pumped from the bottom of the tank. The mass ratio of the extract liquid lost:solid particle settled was similar to the corresponding ratio for decanter centrifugation. Settling promises to be a cost-effective method of separating extracted particles from alcoholic extracts with low extract liquid dilution. Published by Elsevier Science B.V.