RESUMO
In the process of grain processing for ethyl alcohol, practically only carbohydrates are consumed, which are presented mainly in the form of starch. The remaining components (protein, fats, fiber, minerals) in transit pass into the grain fiber remaining after distillation of the alcohol from the mash. Distillery grain fiber surpasses wheat bran in its indicators, since during the processing it is enriched with biomass of alcohol yeast. In addition, there is a technological possibility of its additional enrichment with protein, amino acids, and vitamins due to changes in the modes of alcoholic fermentation. The aim of the work was to assess the influence of the mode and conditions of alcoholic fermentation on the composition of distillery grain fiber. Material and methods. Under laboratory conditions, samples of grain fiber of alcohol production were obtained by the method of fermentation samples from wheat under various fermentation conditions. In the obtained samples, the following parameters were determined: protein according to Barnstein, crude protein, vitamins B1, B2, B6, E, as well as the amino acid composition. The volume fraction of ethyl alcohol, the mass concentration of fermentable carbohydrates, and the concentration of yeast cells were determined in intermediate products of alcohol production. Results and discussion. Studies on the effect of yeast from various manufacturers on fermentation rates, biomass growth and grain fiber composition showed the advantage of race Y-717 in terms of alcohol accumulation (11.5% vol.), Fermentation rate (56 hours) and yeast cell concentration (260 million/cm3), which was 15-30% more than in other options. However, from the point of view of increasing the content of protein according to Barnstein and crude protein in samples of grain fiber with yeast Y-717, an increase of only 3-4% was noted compared with other options. This was associated with a decrease in the concentration of yeast by 72 h of fermentation due to autolysis. Studies on the influence of the initial yeast concentration on the growth of biomass, the fermentation rate and grain fiber indices showed that with an increase in the initial yeast concentration from 15 to 45 million/cm3, the fermentation time reduced to 48 h, the biomass growth at the end of fermentation was 20%, the protein in grain fiber increased by 15%, the content of vitamins B1, B2, B6 and E as well as amino acids increased by 13-17%. Conclusion. According to the results of the studies, the technological possibility of enriching distillery grain fiber with protein, amino acids, and vitamins due to a change in the fermentation process during the processing of grain raw materials to alcohol is shown. In particular, this could be achieved through the use of yeast with a high growth rate, by increasing the concentration of yeast biomass, shortening the fermentation period and preventing yeast autolysis at the maturation stage.
