All alcoholic beverages are made by fermenting a sugar solution (a.k.a. a fermentable substrate) with yeast, a process that converts the sugar (C6Hi2O6) to ethanol (C2H5OH) and carbon dioxide (CO2). Usually, one does not start with a pure sugar and water substrate, but with fruit juices for wine, mashed grains for whiskey, molasses for rum, and many others. Regardless of the sugar source the alcohol is the same.
In addition to the variations imposed by the source of sugar, the yeasts themselves and the conditions under which they are used also make their contribution to the character of the final product. This is because yeasts produce small quantities of other substances known as "congeners" in addition to the main product, ethanol. It is no wonder, therefore, that the flavour, colour, aroma, and general quality of fermented beverages vary so widely.
No alcoholic beverage (with the possible exception of vodka) consists simply of alcohol and water with no other constituent present. If it did, it would be colourless, odorless, and tasteless. The colour, aroma, and flavour of beers, wines, and spirits are due to the congeners present.
Alcoholic beverages can be divided into two broad categories according to whether or not there is a distillation stage following fermentation. Beer and wine fall into the non-distilled category whereas whiskey, rum, brandy, gin, etc. have all been distilled. The latter are often referred to as "spirits" or "hard liquor".
Wine and beer are produced by fermenting their respective substrates (i.e. fruit juices for wine, grain mash for beer) with yeast, then clearing, aging, and packaging the fermented substrate as the finished wine or beer.
Distillation - what is it?
Distillation is simply the heating of a liquid to the boiling point followed by condensing the vapours on a cold surface back into a liquid. To remove the hardness from water it can be boiled in a kettle and the steam that is produced condensed against a cold surface to give pure water free of minerals and dissolved ions. The calcium and magnesium salts that constitute the hardness remain behind in the kettle. Nature carries out Her own distillation in the form of rain. The sun evaporates water from the surface of lakes and oceans leaving salt and impurities behind. Clouds form, condense, and a close approximation to pure water falls to Earth.
So distillation is not a mysterious subject, nor is it threatening. It is as commonplace as a rain-shower or a teakettle boiling and causing condensation on a nearby window.
As you can imagine, the actual practice of distillation as a controlled procedure is a little more complicated than this and later chapters will provide an exact description of how to build the equipment required and the procedures involved in operating it.
There are actually two different types of still, the choice of which to use depending on the level of purity required in the product. Traditionally, whiskey is made in one type, a pot still. It's rather simple in design because only a moderate level of purity is required. Gin and vodka production on the other hand requires a more sophisticated type of still called a fractionating still because a very high level of purity is desired. A detailed description of the two types will be provided in the chapter on Distillation because it is quite important for the reader to appreciate the differences.
However, in this text the high-separation type of still is chosen over the traditional pot still for making whiskey because of the exacting control it affords over the level of separation. High-separation stills can be operated in a manner whereby they give much less than maximum separation, which is exactly how they are very efficiently used to make whiskey. This is covered in detail in the Distillation chapter.
An advantage that falls out of this is that the high-separation still can also be used to produce pure ethanol for making gin and vodka. For a well-written text on how to do this read, John Stone Making Gin and Vodka, www.gin-vodka.com. The high-separation still design described in this text can be used to make gin and vodka exactly as described in that book.
As mentioned before, the fermentation of sugars derived from grapes, barley, corn, potatoes, molasses, milk or any other source produces a wide variety of chemicals, the major one being ethyl alcohol (ethanol). Minor constituents will be propyl, butyl, and amyl alcohols. These minor constituents are collectively called "fusel alcohols" (in the past they were called "fusel oils", but they're not oils they're higher alcohols). They are responsible for the unpleasant side effects of drinking such as headaches and hangovers.
When such a mixture is distilled, the first vapours to come over will be rich in the more volatile components such as methanol and acetone. This first fraction is referred to as the "foreshots". There is no sharp separation so, long before the foreshots are completely exhausted, the ethanol begins to appear but is collected into a "heads" phase to buffer the transition between the foreshots and the beverage alcohol. Later, when the ethanol phase is tapering off, the "tails" begin to emerge. These are the least volatile components of the mixture. At first, come the less volatile esters, and then the propyl, butyl, and amyl alcohols known as fusel alcohols. Thus, in a simple distillation using a pot still there are four main fractions: the foreshots; the heads; the middle run; and the tails. The middle run is mainly ethanol with trace amounts of heads and tails, the amount of each depending on where the cut-offs are made.
As mentioned above, simple distillation of a mixture of liquids does not produce a clear-cut separation of the various components. If such a separation is required it is necessary to resort to the use of a fractionating column. The theory and practice of this will be described in detail in a later chapter but a few words will be said about it here. The procedure involves the use of a vertical column attached to the top of the boiler. The column is packed with inert particles such as short lengths of glass tubing known as Rashig rings, ceramic "saddles", wire gauze, or in fact any non-reactive material with a large surface area.
The vapours from the boiling liquid pass up the column, are condensed to a liquid at the top, and run back down through the packing in the column. This counter-current flow of vapour up and liquid down has the effect of producing a series of mini distillations at the surface of each piece of glass or metal in the column. It is equivalent to carrying out a simple distillation in a pot still and then redistilling the product over and over again. The final result is an almost perfect separation of the mixture into its various components, allowing each one to be drawn off in sequence from the top of the column in the order of its boiling point. Thus, the most highly volatile components emerge first while the least volatile components emerge last.
Whiskey, Brandy, Rum, etc.
The distillation of these products is done using a pot still or a special-purpose fractionating still, and this effects only a crude separation of the fermented substrate into foreshots, heads, middle-run, and tails. The skill in making a palatable whiskey consists of: mashing the grains into fermentable sugars; fermenting the mash under conditions that give rise to a certain mixture of chemicals; and, distilling the mixture and discarding a portion of the heads and a portion of the tails.
The middle fraction, consisting chiefly of ethanol, will also contain the retained portion of heads and tails (i.e. the congeners). It is these congeners that impart the characteristic flavour and aroma. At this point there is no colour. Colour is imparted by storing the spirits in oak barrels for a number of years, a process that also modifies the chemical make-up of the whiskey to give unique characteristics of a particular distiller.
Corn whiskey is the whiskey produced by mashing corn (i.e. using malt enzymes to convert its starches to sugars), fermenting the corn mash with yeast, and distilling the fermented mash. The mashed corn produces a particular profile of congeners that characterizes the flavour of corn whiskey.
Historically, the distillers of corn whiskey took pride in the tradition of producing whiskey and made their whiskey entirely from grain and malt. But, with the advent of the prohibition (U.S. 1921-1933) there was a surge of new distillers who had no particular attachment to whiskey making as an art or historical tradition. These new prohibition distillers became notorious for stretching their corn mash with sugar. Some recipes were less than 10% corn, the rest being sugar and water. While using sugar to produce a "thin mash" will produce as much alcohol and with much less effort, the flavour of the finished whiskey is very harsh, thin, and insipid. This prohibition type of corn-whiskey production became so prevalent that whiskey made from pure grain (i.e. no sugar) became a rare delicacy, and was attributed the name "pure corn whiskey". Unfortunately, when the prohibition ended these sugar recipes persisted into the subsequent generations of corn-whiskey distilling so the traditional pure corn whiskey remained a scarce commodity.
Note: Commercial whiskey producers are bound by law to use all grain in their mashes, and no spirit made with sugar can be called "whiskey".
For a more detailed account of the history of corn whiskey during the prohibition read, Joseph E. Dabney, Mountain Spirits, Asheville NC, Bright Mountain Books.
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