Effective diffusion coefficients of glucose and ethanol in corn grits were estimated as a factor affecting the velocity of solid-state ethanol fermentation by using the Crank's equation. Experimental results showed values about 1/5 of the molecular coefficient in water. The 90% response time of diffusion was 5 to 10 minutes in well stirred solution. This means that the diffusion rates are evaluated to be larger than the rates of changes in solute concentration, and that effects of concentration distribution of these substances are negligible in the course of conventional solid-state ethanol fermentation of corn grits.
Small scale brewing experiments were carried out by using various cereals (rice, maize, rye, barley, buckwheat, and Job's tear) as raw materials. The activity of a-amylase, glucoamylase, and a-glucosidase in maize-koji was the lowest of the seven.The a-glucosidase activity in buckwheat - koji was the highest.The fermentation recoveries of maize-and buckwheat-shochu were lower than the others because of their low dissolution efficiencies.Each of the shochu made from various cereals had its characteristic flavor.
“Hineka”, an off-flavor caused by overaging of sake, was effectively eliminated, by treating overaged sake with immobilized cells of S.cerevisiae Z-8 at 15°C for 3 days, and the taste and flavor of the sake were improved in sensory evaluation. The removal of 3-Hydroxy-4, 5-dimethy-2 (5 H) furanone, a main flavor component of hineka, from aged sake was also confirmed by using gas chromatography.