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For several years, enthusiastic distillers have been mastering a new direction in distillation – vacuum distillation, which is also romantically called “space distillation”. The principle itself has been known to chemists for a long time and is used in the oil industry, but for moonshining this is a new topic, which, due to its specificity, has managed to acquire myths and legends. It’s time to figure out what it is.
Attention! I have never practiced vacuum distillation and have never even tried vacuum moonshine. This article is just a side view.
Theory
At normal atmospheric pressure (760 mm Hg or 1 atmosphere), the boiling point of water is 100 ° C, alcohol – 78,37 ° C. The physics of the process is such that with a decrease in pressure, the boiling point of liquids also decreases. It has been established that with a decrease in pressure by 0,5 atmospheres (380 mm Hg), the boiling point of alcohol decreases by 15 ° C, that is, boiling occurs at 63 ° C.
Vacuum distillation is the process of separating ethyl alcohol from other mash components under reduced pressure in a closed system that has no connection with the atmosphere. It should be noted that the name “vacuum” does not accurately convey the essence of the process, since creating a vacuum (that is, a space free from any substance) at home will not work, and it is not necessary. In order not to mislead users, it is more correct for proponents of this distillation method to call it “discharged”, “low atmospheric”, etc., but not “vacuum”.
Vacuum distillation can be single-pass (wash – finished distillate) and two-pass (wash – raw alcohol – finished distillate, this is an analogue of the second distillation in the classical scheme). Interestingly, most advocates of vacuum distillation of moonshine use a one-pass method, believing that this is enough to remove harmful impurities. Some distillers first obtain raw alcohol by the vacuum method, and then do repeated fractional distillation in a classic distiller (at atmospheric pressure), a combined scheme is obtained.
Moonshine still for vacuum distillation
If compared with a conventional distiller, then a pressure sensor and a vacuum pump with at least the simplest automation are additionally required, they also seal all connections and the receiving container of moonshine, making the distiller a closed system. In most designs, the sensor takes readings from the receiving tank, and the pump is also connected to it.
The process of vacuum distillation occurs as follows: the distiller sets the desired pressure in the system on the sensor, the pump pumps air out of the apparatus to the required value, creating a vacuum. Next, the mash is heated and distilled as usual.
To separate the distillate into fractions (“heads”, “body” and “tails”), several receiving containers are used, into which the finished product is admitted through a “flow divider” – several tubes leading from the refrigerator to different receiving containers. When collecting the “heads”, the tap is opened to the first container, and when collecting the “body”, the first tube is blocked and the distillate is sent to the second container.
If everything is simple in theory, then in practice the apparatus for vacuum distillation differs significantly from the classical one, since a number of problems need to be solved, here are just a few of them:
- the cube must be thick-walled and with stiffening ribs – when rarefied, the external atmosphere begins to put pressure on the walls from the outside, and if they are thin, then the cube can be crushed like a tin can;
- complete sealing – clamp connections, holes for thermometers and tubes, as well as other elements should not let air through even minimally, otherwise normal vacuum will not work, the pump will constantly pump out air;
- at low pressure, foaming in the wash and the steam velocity in the column increase significantly. As a result, it is more difficult to control distillation and fractionation; additional design solutions or a complete redesign of the refrigerator are required;
- each receiving container must have not only a tube for supplying distillate, but also at least one tube for pressure equalization. As a result, the device is overgrown with an incredible number of tubes, faucets and adapters, they need to be connected correctly and know when to open / close flows.
All this was reflected in the cost of vacuum distillers. At the time of writing (23.03.2020/29981/12), I saw the cheapest vacuum distillation kit at a price of 60 rubles, while its cube volume is only 165 liters. More advanced and voluminous models cost XNUMX-XNUMX thousand rubles.
Benefits of Vacuum Distillation of Moonshine
Equipment sellers consider the high quality and outstanding organoleptic properties of the drink to be the main advantages of vacuum distillation. True, I could not find a single explanation in which the differences from the classical version would be clearly and in detail described. It is believed that low temperature preserves the taste and aroma of the feedstock better, so the distillate is “fresh” than the traditional “compote” brewed closer to 100 ° C.
However, here too everything is foggy. For example, the adherents of the method stated that vacuum distillation is equally good for both grain and fruit brews. I think that in the case of grain raw materials, “freshness” will harm. For example, if whiskey has hints of bread precisely due to the high temperature of distillation, then it turns out that from the same mash, “fresh” low-temperature vacuum moonshine will have notes of sprouted grain. But this is just a guess…
In theory, higher quality can be obtained due to shorter boiling time and temperature. As a result, the protein is not denatured, the esters almost do not decompose, and less heavy impurities get into the finished product. But the theory always needs to be proved by practice, for example, by a chromatogram of two distillates from the same mash. Vacuum apparatus manufacturers, selling their distillation kits for space money, have not yet bothered to make a chromatogram that is relatively cheap compared to their prices, which is strange …
Also, the advantage of vacuum distillation is energy savings and shorter distillation time compared to the classical method.
Attention! In some articles about vacuum distillation, it is written that the resulting drink is absolutely safe and does not cause a hangover. This is outright misinformation, because you can argue about the degree of harmfulness and severity of a hangover, but not about their absence. The nature of alcohol is such that it in itself harms the body, even without taking into account other impurities in the composition.
Disadvantages of Vacuum Distillation
The main and most obvious disadvantage of vacuum distillation is the high cost of equipment. Few can afford to pay for this hobby. And this despite the fact that the advantages of the method have not yet been proven.
Also, a complex system requires an understanding of the processes and preliminary preparation of the distiller – in inept hands, a vacuum moonshine still can be dangerous, however, like any other.
Prospects for vacuum distillation of moonshine
For me, an indicator is the fact that over the decades of the existence of this method, not a single powerful alcohol concern has introduced vacuum distillation into its technological processes.
Yes, Irish and Scottish whiskeys, French cognacs and many other alcoholic beverages have a strictly regulated, unchanged production technology, where it is unrealistic to do this.
However, it is possible for companies to mass-produce grape brandy or malt distillate in countries where control is based on the final product (content of substances in the composition), and not on production technology. Moreover, the benefits are obvious: savings in energy and distillation time, combined with the same level of quality (or even higher) as traditional drinks, promises a good profit. Apparently there are barriers…
Of the large companies, Bacardi makes timid attempts in the direction of vacuum distillation with its brand of Oxley gin, but these are small batches, as the manufacturer himself writes, craft gin, and there is no talk of more or less mass production yet.
My interest in vacuum distillation can only be revived by the appearance of industrial analogues of vodka, whiskey or brandy from eminent alcohol concerns, and now it is more and more like marketing tricks of equipment sellers and boasting of owners of expensive devices, such as they are chosen and drink what they cannot afford other.