Separation of particles from ethanol/maize extracts: An inexpensive alternative to centrifugation

An important aspect of extraction using an organic solvent that is often ignored in many laboratory scale studies is thorough solvent recovery. Although most of the solvent can be recovered with a centrifuge, the solvent left on the ‘dry’ stream must be evaporated. A custom built pilot-scale settling tank was used to separate maize particles from ethanol extracts into water with little dilution of the extract liquid. The larger particles that settled in the first one-fourth of the tank were carried out by a continuous water flow 76 cm below the extract layer. The large particles had 80% higher protein mass fraction than the smaller particles that collected in the bottom of the settling tank downstream from the extract inlet. Water flow was confined to the bottom of the tank and extracted particles were prevented from accumulating in the settling tank with a much lower water/extract flow rate ratio than needed for a smaller settling tank. The mass ratio of entrained extract liquid/settled solids (0.5) was one-half that observed in previous methods using smaller tanks. This is caused by a more stable extract/water interface. The yield from finer, 1 mm meal, was slightly lower than 2 mm meal and increased extract liquid entrainment. Consequently, the 2 mm particle size is the minimum that should be used with this process.