Effects of ground corn particle size on ethanol yield and thin stillage soluble solids

The effects of ground corn particle size on ethanol yield and soluble solids in thin stillage was evaluated using a 2-L laboratory dry-grind procedure. The procedure was optimized for grinding, liquefaction, saccharification, and fermentation parameters. The optimized procedure was reproducible with a coefficient of variation of 3.6% in ethanol yield. Five particle size distributions of ground corn were obtained using a cross-beater mill equipped with five screens (0.5, 2, 3, 4, and 5 mm). Particle size had an effect on ethanol yield and on soluble solids concentration in thin stillage. The highest ethanol yield of 12.6 mL/100 mL of beer was achieved using a 0.5-mm screen in the cross-beater mill. Treatment using the 0.5-mm mill screen resulted in soluble solids concentration of 25.1 g/L and was higher than soluble solids concentrations obtained with other screens. No differences in soluble solid concentrations were observed in samples of thin stillage obtained from 2, 3, 4, and 5-mm screens which had a mean yield of 16.2 g/L. By optimizing particle size for maximum ethanol yield and minimum solids in thin stillage, dry-grind corn plants could realize reduced capital and operating costs.