Effect of Wet and Dry Fractionation Methods on Ethanol Production from Hard and Soft Endosperm Corn Types

Abstract

Two corn fractionation methods, wet and dry, were compared to the conventional dry grind process using hard and soft endosperm corn types. Fractionation methods remove germ and pericarp fiber prior to fermentation. Wet fractionation involves soaking of corn and grinding, followed by germ and pericarp fiber removal. In dry fractionation, corn is tempered and passed through a roller mill before the germ and pericarp fiber are removed. Hard and soft endosperm types differ in the protein starch interactions, shape of starch granules, and type of proteins present. Effect of hard and soft endosperm on wet and dry fractionation processes and the conventional process were analyzed for final ethanol concentrations and fermentation rates. Germ from fractionation processes was analyzed for yield, oil, protein, and residual starch contents. Pericarp fiber yields, residual starch, and NDF contents were determined. Soft endosperm corn resulted in higher final ethanol concentrations (15.8%) than hard endosperm corn types (15.5%). Germ yields from hard endosperm corn were 1.8% higher than soft endosperm corn types. Pericarp fiber yields were higher from soft endosperm corn (10.8%) than from hard endosperm corn (8.35%). Among processes, wet fractionation resulted in 0.5% and 1.8% v/v higher final ethanol concentrations than dry fractionation and the conventional process, respectively. Germ yields were higher from dry fractionation (10.6%) than from wet fractionation (8.35%). Germ fractions from wet fractionation had higher oil (31.4%) and protein (14.2%) than germ from dry fractionation (18.8% and 12.6%, respectively). Dry fractionated germ had 6.9% more starch than wet fractionated germ. Pericarp fiber yields were higher from wet (11.4%) than from dry (7.21%) fractionation. Fractionation processes result in higher final ethanol concentrations and can provide valuable coproducts.