Cereal Chem 72:360-364  |  VIEW ARTICLE

Production of Fuel Alcohol from Hull-less Barley by Very High Gravity Technology.

K. C. Thomas, A. Dhas, B. G. Rossnagel, and W. M. Ingledew. Copyright 1995 by the American Association of Cereal Chemists, Inc. 

Very high gravity mashes (greater than 30 g dissolved solids per 100 ml) were prepared from an experimental hull-less barley (SB90354) and fermented with active dry yeast. A maximum ethanol concentration of 17.1% (v/v) was realized in fermented mash, and a total ethanol yield of 443 L per tonne of barley (dwb) was obtained. To prevent excess viscosity during mashing, it was necessary to hydrolyze beta- glucan in ground barley using crude preparations of beta-glucanase or Biocellulase. While both these preparations possessed an endoglucanase activity, no measurable exoglucanase activity was detected. A typical mash prepared at a water-to-grain ratio of 3:1 and without hydrolysis of beta-glucan had a viscosity of 2,480 BU, while the viscosities of the mashes prepared after hydrolysis of beta-glucan with beta- glucanase or Biocellulase were 560 and 240 BU, respectively. Hydrolysis of beta-glucan not only reduced the viscosity of the barley mash but also released water bound and trapped by the beta-glucan gel. The free amino nitrogen (FAN) content of the barley mashes was high when compared to wheat mashes, and about 80% of this FAN was taken up by yeast. In spite of the high FAN content of the mash, an exogenously added nitrogen supplement stimulated yeast growth and fermentation.