Characterisation of fermentation of high-gravity maize mashes with the application of pullulanase,proteolytic enzymes and enzymes degrading non-starch polysaccharides

The aim of the research was to assess the possibility of the fermentation productivity rising through the increase in corn mashes extract from 16–17 to 20–21°Balling, yet keeping a 3-day fermentation period. The second goal was to obtain the highest possible utilization of starch in the raw material through deep enzymatic degradation and utilization of available sugars and simultaneous maintenance of high quality spirit. It was found that fulfilling the above during the 3-day fermentation period was possible with the application of pullulanase as an additional amylolytic enzyme. Adding pullulanase resulted in the acceleration of the starch hydrolysis degree, which led to lower amounts of unhydrolyzed dextrins and higher ethanol yield. When the supportive enzymes complex (pullulanase, protease and cellulase) was used, the final ethanol concentration reached 10.86 ± 0.04% v/v, with ethanol yield at 68.41 ± 0.23 dm³ of absolute ethanol (A₁₀₀) per 100 kg of starch, which was 95.25 ± 0.32% at the theoretical value. The acceleration of starch enzymatic degradation and the application of a proteolytic preparation visibly shortened both initial and main fermentation phases. This in turn increased the time of the final fermentation phase and resulted in more extensive utilization of substrates by yeasts with simultaneous reduction of the final concentration of acetaldehyde (26.0 ± 0.5 mg/dm³A₁₀₀) and diethyl acetal of acetaldehyde (2.5 ± 0.5 mg/dm³A₁₀₀). The quality of spirit obtained was positively verified also in terms of relatively low concentration of higher alcohol (3912.2 ± 9.8 mg/dm³A₁₀₀). Preliminary analysis of costs (without raw-material) of 1 l distillate production indicated the possibility to reduce the costs by 18–20%.