Vacuum fermentation
It has been established that fermentation under vacuum conditions has a number of specific features that make this technology particularly promising, especially for the production of high-quality alcohol. Under vacuum conditions, alcohol is distilled directly in the fermenter and immediately removed after it is formed. As a result, fermentation takes place at a practically zero alcohol concentration. The productivity of alcohol production and the equipment increases by 2 to 3 times. The viability and activity of the yeast remain stable throughout the entire fermentation cycle. The alcohol yield from 1 tonne of starch complies with established production standards. The hydration ratio of the mash can be reduced to 1:1. Foreign microflora and the products of their activity are practically absent under these conditions. The alcohol distillate reaches a concentration of 35%, which allows it to be fed directly to rectification without the use of a beer column. At the end of fermentation, the dry matter content increases to 26 to 30%, resulting in concentrated post-distillation stillage with a crude protein content of 32 to 36%, calculated on a dry matter basis.
Process Flow Diagram
The principal process flow diagram shown in the figure includes the following main operations: grain grinding and mash preparation; thermo-enzymatic treatment of the resulting grain mash at a hydration ratio of 1:1; fermentation of the prepared mash in a fermenter under vacuum conditions with simultaneous removal of the water alcohol vapour and its subsequent condensation into alcohol distillate; and drying of the post-distillation stillage.
Figure: Process Flow Diagram of the Vacuum Fermentation Process
The vacuum fermentation process changes the composition of impurities in the rectified alcohol. The concentration of certain impurities that are difficult to remove during rectification is significantly reduced, while some are completely eliminated. The total content of fusel oils and volatile acids is approximately two times lower than that obtained with conventional fermentation.
Rectified alcohol obtained from the distillate is characterised by high organoleptic properties. The dry matter content of the post-distillation stillage reaches 26–30%, which simplifies its further processing and reduces energy consumption.
The resulting post-distillation stillage is a valuable protein and vitamin feed additive, containing at least 32% crude protein on a dry matter basis and having high biological value.
