Factors influencing the fermentation process and ethanol yield

The factors which influence ethanol yield are: the quantity of fermenting sugars from raw material, the heating temperature of the mashes, the fermentation time, the distillation parameters. Out of the already-mentioned factors, the heating temperature of the mashes and the fermentation time have been studied. From the analyzed data it has been found that the highest percentage of alcohol can be obtained in the case of non – cooked wheat and corn mashes. In the case of cooked mashes the highest quantity of ethanol is released in the first 46 hours of the process, fact that recommends the use of a short type fermentation process for cooked mashes which ensures greater productivity. In the case of non-cooked mashes the recommended process is the longer one (72 hours) because ethanol is produced continuously, the sowed yeasts are resistant to alcohol and the osmotic stress caused by fermenting sugars is reduced compared to the process based on cooked mashes. Contamination with Lactobacillus is missing in the case of cooked mashes, and in the case of non cooked mashes it appears only at the end of the process, with a density of 1-2 bacteria per field. Compounds of the distilled mixture and their quantity have been determined by means of the gaschromatographic analysis.