Vacuum fermentation
It has been established that fermentation under vacuum conditions exhibits a range of distinctions, making this technology highly appealing, particularly for producing high-quality alcohol:
— Under vacuum conditions, alcohol distillation takes place directly in the fermenter at the boiling temperature, and it is removed from the liquid phase as it forms. Thus, fermentation practically occurs at zero alcohol concentration in the mash.
— The rate of alcohol production (and consequently, equipment productivity) is increased by 2 to 3 times.
— Yeast viability and activity are maintained at their initial levels throughout the fermentation cycle.
— The alcohol yield per 1 ton of starch remains at least at the established norms.
— The dough hydration ratio can be set at 1:1.
— Foreign microflora is practically absent in the fermenter when working with such hydration ratios. Impurities synthesized by pathogenic microflora are also absent.
— At the fermenter outlet, the concentration of alcohol distillate is 35%, allowing it to be directed directly to rectification (in the production of food-grade alcohol), eliminating the need for a rectification column in the setup.
— Towards the end of the fermentation cycle, due to water evaporation, the dry matter content in the liquid phase of the fermenter increases to 26-30%. This liquid, containing 32-36% crude protein (calculated on an absolute dry matter basis), is essentially concentrated distillers’ grains.
The fundamental equipment-technological scheme shown in the figure includes the following operations: grain grinding and mash preparation; thermo-enzymatic treatment of the grain mash obtained with a hydration ratio of 1:1; fermentation of the resulting mash in a fermenter under vacuum conditions, with simultaneous distillation of water-alcohol vapor, followed by condensation into alcohol distillate; drying of post-distillation distillers’ grains.
Figure: Equipment-technological scheme of the vacuum fermentation process
The vacuum fermentation process alters the composition of impurities in the distillate obtained through rectification. There is a noticeable reduction or complete absence of several impurities that are difficult to remove during rectification. The total amount of fusel oil and volatile acids fractions obtained during vacuum fermentation is twice less than the content of similar fractions in the control.
The alcohol rectificate obtained from the distillate has high organoleptic indicators.
The concentration of dry matter in the post-distillation distillers’ grains using this technology is 26-30%, significantly simplifying the equipment process and reducing the energy costs required to bring the product to its final marketable forms.
The resulting post-distillation distillers’ grains are a valuable protein-vitamin additive, containing no less than 32% crude protein in a dried form, with high biological quality.
