Influence of various yeast strains and selected starchy raw materials on production of higher alcohols during the alcoholic fermentation process

The formation of volatile by-products during alcoholic fermentation is affected by many factors such as the type of yeast strain applied, technological parameters of the process and the raw material used as the main constituent of the fermentation medium. The influence of availability of sugars released by the plant polysaccharide hydrolysis on the concentration of higher alcohols during the fermentation process was analyzed. Significant differences in the starch hydrolysis dynamics for various raw materials, entailing changes in availability of sugars such as glucose, maltose, maltotriose and maltotetraose, are reported. The highest glucose concentration after the mashing process (93.8 +/- A 3.8 mg cm(-3)) was observed for the maize mash (as compared to that of the rye and amaranth mashes, 24.9 +/- A 0.9 and 46.9 +/- A 2.5 mg cm(-3), respectively). The highest glucose content in the maize mash resulted in a significantly higher isobutanol and 2-methyl-1-butanol content at the initial stage of fermentation, irrespective of the yeast strain used (D-2 or As-4). The highest final total content of fusel alcohols (ca. 5,460 mg dm(-3) EtOH, on average) was also found in the distillates produced from the maize mash. However, the concentration of higher alcohols in the rye and amaranth distillates was similar and reached the level of ca. 3,440 mg dm(-3) EtOH, on average. It is shown that the polysaccharide hydrolysis rate, and hence the rate at which fermenting sugars are released, significantly affects the concentration of higher alcohols in the produced distillates.