Distillation – Supercharging Alcohol
Who invented distillation? Like the claim to being the world’s greatest lovers, who can know for sure? Credit for distillation will continue to be contested by many until the next parchment or cave painting with even the remotest suggestion of the technique is discovered.
However, distillation is such a basic process that any caveman who ever boiled herbs would have noticed its aromatics in the vapor. Capturing this vapor would then have been a natural extension when those vapors naturally condensed over a cooler surface. Universally, once this rudimentary process was understood, the earliest uses of distillation were probably for the extraction of herbal oils for medicines or for their fragrance. In its simplest form, distillation is just boiling water and collecting its vapor. This vapor will have less impurities than the liquid which was boiled.
In the alcoholic beverage industry, we distil for two reasons. Firstly, to extract a higher concentration of alcohol than the original charge or base alcoholic liquid. This could be fermented molasses, cereals, cactus juice or a wine. As alcohol has a lower boiling point than water, it leaves the charge more readily than water, giving the vapor a higher alcoholic content than the original charge. We collect this vapor by cooling it to a point where steam changes state back to a liquid called the distillate. By re-boiling this distillate and repeating this process we can achieve increasing concentrations of alcohol. However, there is an azeotropic point or limit at around 97.25% of alcohol by volume (ABV) where further re-distillation will not increase this percentage at room pressure. This is due to the natural attraction of water and alcohol molecules whereby there will always be some water clinging on to the alcoholic fumes.
The second reason that is often overlooked is the extraction of flavors from the base alcoholic charge. This is particularly important for spirits such as whisky, brandy, grappa, rum, tequila etc when the essence of the base product is sought after for its distinctive character. On the other hand, potable neutral spirit, sometimes termed Grain Neutral Spirit (GNS) or Neutral Grain Spirit (NGS), are distilled to a high degree of at least 96% ABV to be more or less devoid of flavor and essence. As alcohol molecules are identical regardless of the base raw material from which the charge is derived, we are left with only 4% or less of water containing flavor compounds or congeners in the case above. These congeners give aromas and taste from the fermentation process as well as characteristics of the raw material from which the charge is derived. An 85% ABV distillate will therefore contain 15% of flavored water which packs a bigger punch of fuller flavors than the 96% ABV neutral distillate. The trade-off is thus between producing a more alcoholic but tasteless spirit over a lower-strength alcoholic spirit with more flavor. For this reason, rules governing Bourbon production stipulates that it be distilled to no more than 80% ABV.
Clean neutral spirits are however important for producing “white” spirits such as vodka and gin as they undergo additional processing and infusion of botanicals or flavors for specific characteristics. Because GNS are not produced for their flavors, they are often made from the cheapest available agricultural ingredients that are rich in sugars which can easily be converted to clean alcohol. These base materials could be rice, sweet potatoes, potatoes, corn, wheat, molasses etc.
Alcoholic distillation is carried out in two very different looking stills, although there are many variations and hybrids of these two fundamental systems. The industrial column still – introduced previously in issue #2 of Cask and Dram – is almost always used in the production of GNS as they are highly efficient in output as well as generating high ABV distillates . The other, the ubiquitous pot still, has been featured in many ancient manuscripts and drawings. In this article, we will use its primary concept for our understanding of basic distillation. The pot still is simply a receptacle for boiling the base liquid, a lid that captures the vapors and a neck that channels these vapors onto a condensing unit. Malt whiskies from Scotland have traditionally been distilled twice in pot stills with some notable exceptions being the Auchentoshan distillery in the Lowlands, the Hazelburn brand from the Springbank Distillery in Campbeltown and Benriach’s Horizons from Speyside, all of which are trice distilled mirroring the process of Irish distilleries. Other variations are 2.5 times for Springbank and even a very odd 2.81 times distillation by Mortlach which has concocted a complicated regime of wash, low wines and spirits still usage.
In a twice distilled system, the fermented wort (wash) becomes the material (charge) for the first (wash) still. In a distillery, wash stills are easily identified as they have windows along the sides of the neck. When wash is boiled too rapidly, excessive foaming and entrained droplets of the wash can be carried over the neck of the still contaminating any distillate that may have already been collected. Oval windows allow the stillman to observe for such boiling overs and to make adjustment to the heating.
The next part of the system in distillation are the condensers that turn the vapors being channeled up the neck of the pot back into a liquid. These days, more complicated shell and tube condensers have replaced the traditional worm and tub setups. The principle is the same – cool the vapors by running cold water between the vapor carrying pipes thus condensing it into a liquid distillate. Not all the distillate that is collected flows directly into the second (spirit) still. As the alcohol content in the distillate falls over the course of distillation, there will be a point at around 1% ABV where continued distillation becomes uneconomical and the first distillation is then deemed complete. The cutoff point is mechanically made by the use of a rectangular windowed steel or brass casing called the Low Wines Safe which channels the remaining low ABV distillate away from the second distillation.
The usable distillate from the first distillation is called low wines but its volume is significantly less than the wash used in the first distillation as the stillage or residue from the first distillation makes up about 65% of the original wash. Pot ale, the solid component of this residue, is mixed with the draff or residue from the mash (see issue #3 of Cask and Dram) and used as animal feed. The second or spirit stills are smaller than wash stills as the low wines that now becomes the charge has a much smaller volume than the wash in the first still. Having been distilled once, low wines are more refined than the wash used in the first still, therefore there is significantly less risk of boiling over. With little fear of entrainments contaminating the distillate, spirits stills do not require windows. This absence of windows in spirit stills coupled with their smaller construction is how one can identify the differences between the two types of stills, a trinket of trivia that could earn you an extra dram or so at distillery tours.
After the second distillation of low wines in the spirit still, the collected distillate passes through the “spirits safe” so called as they were once controlled by the excise man who tightly held the keys to this “safe”. The spirits safe splits the distillate from the second distillation into the heads, hearts and tails, or foreshots, newmake and feins respectively. The initial flow of distillate or the heads are pungent and impure and is channeled back into the spirit still of the next batch. The skill of the stillman is to recognize the cut point for when to collect the heart which becomes the new make that is filled into cask to eventually become whisky. Again, when the concentration of usable alcohol falls below economical levels, the stillman makes the next cut for the tails which have unpleasant aromas and flavors and so is redistilled. The residue or spent lees at the bottom of the spirit still contains copper and is usually discarded or used as fertilizer.
In spite of being a relatively rudimentary process it is heartening to know that there are contemporary innovators and champions of the distilling industry. Bill Lark took on the establishment to help overturn the archaic Australian Distillation Act of 1901 requiring wash stills be at least 2,700 litres capacity. In the good or rather bad old days when excise men were armed and embroiled in lethal cat and mouse games with moonshine distillers, smaller stills were outlawed as they were easier to lug around covertly. This law made identification of illicit wash stills easier as anything smaller than the 2,700 litres capacity were automatically deemed illegal and destroyed.
This strict attitude towards alcoholic beverages by the authorities were partly cultural but more so to generate tax revenue particularly in the British Crown’s sphere of influence. However, in other parts of the world, particularly continental Europe, distillation wasn’t so strictly controlled. This lead to innovators such as Giobatta Poli to design a small mobile still that could go from farmhouse to farmhouse processing the leftovers of a wine’s crush called the marc to be distilled into that traditionally rustic Italian digestive called grappa. Four generations later, Jacopo Poli refined an almost forgotten 19th century vacuum still design, enhancing it with heating from a bain-marie rather than by direct heat. This system could generate evaporation at very low working temperatures of 38 – 65 °C, lower than the boiling point of ethanol (78.25 °C) at room conditions. This allowed only the lighter congeners to be extracted leaving the heavier, nastier compounds behind. The result, a very elegant distillate with delicate fruity and floral aromatic notes.
However, there are also mavericks to be wary of, not the distillers themselves but rather a new generation of “suave” marketers. A noticeable tendency in the spirits business shadows similar pretentious marketing jargon used in the wine industry over the past 20 years or so. Then, small wineries regardless of quality started to embellish the image of their brands with the use of the term “boutique”. These days, monikers such “artisanal”, “designer” and “craft” are making their rounds in the spirits industry that seem to suggest a premium or exclusively made quality product. Unfortunately, in many instances premium extends no further than their pricing. By design, smaller operations don’t benefit from economies of scale in production, packing and distribution and that’s the main reason they are more expensive, not the spiel marketers are espousing. I say, power to the distiller! They should be given more say to what goes on product labels. Then, there will be more interesting information about the brands’ characteristic production processes and less meaningless marketing verbiage.
Cask & Drams Magazine