Originally By Tony Ackland
INTRODUCTION TO ALCOHOLIC BEVERAGES
What are Alcoholic Beverages?
Alcoholic beverages are any potable (drinkable) liquids containing ethyl alcohol. There are four main types of these products: Beers, Wines, Distilled Spirits, and Cordials or Liqueurs. The amounts of alcohol in each type varies widely. Beers may contain as little as 2-3% while wines typically have an alcoholic strength of 10-14% although certain types (fortified wines such as Porto and Sherry) can go as high as 20%. Cordials/Liqueurs have alcoholic strengths ranging from the high end of the wine spectrum up to 40% or more. Distilled spirits, as their name implies, are the highest, and although the trend today is toward lower strength, spirits will still mostly be found in the 40-45% range, with examples of up to 50% common. There are several specialty whiskies from both Scotland and the United States that exceed 50% and some rums go as high as 75%! According to the Federal Government definition of alcoholic beverages the alcohol content can range from 0.5% to 95%. This definition traces to Prohibition when the government established what an intoxicating beverage was, and it remains in effect despite the fact than an enormous quantity of an 0.5% beverage would have to be consumed before anyone would actually become intoxicated. The uses of alcoholic beverages pretty much coincides with the alcoholic content. The low alcohol products, wines and beers, are normally consumed just as they are. That is, they are drunk straight, or "neat". Cordials and Liqueurs, usually containing significantly higher alcohol percentages, may be consumed straight or mixed, but the amounts used are much smaller relative to beers and wines. Distilled spirits are usually consumed mixed with either water, soda, fruit juice or some other liquid. Various flavorings are also widely used with drinks mixed from distilled spirits; this is uncommon with the other alcoholic beverages.
Classification Of Alcoholic Beverages
Alcoholic beverages are always produced by an alcoholic fermentation. This produces an end product in the case of wines and beers, whereas distilled spirits and cordials/liqueurs must be further processed to extract the alcohol from the fermented beverage.
Fermented Alcoholic Beverages – Definitions
Wine.-The fermented juice of a plant product. Wines are typically made from fruits although it is possible to make them from vegetables, dandelions and other plants. If a product is identified simply as wine, it must be made from grapes. Wine made from other fruits, such as apples, plums, peaches, must be identified by the fruit used (apple wine, plum wine, peach wine). The same regulations apply to wines made from other plants; the plant must be identified.
Beer - A spirituous liquid fermented from a mixture of grains and water.
Mead - A beverage fermented from honey which contains about 8% alcohol. An ancient beverage.
Pulque - Fermented from the milky juice of the Agave plant. It has 4-6% alcohol by volume and is generally drunk fresh, without aging.
Sake - A fermented beverage originating in the Orient. It is made from rice which is cleansed, steamed, and allowed to ferment. Sake contains from 12-16% alcohol.
Fermented and Distilled Alcoholic Beverages - Definitions
Brandy - A product made by distillation of a wine. If the term "brandy" is used by itself, the product must be distilled from grape wine. Brandy therefore means grape brandy. A brandy can be distilled from any type of fruit wine (typically, only fruit wines are used), but in each case, the type of brandy must be identified: plum brandy, cherry brandy, pear brandy and so forth. The most famous brandy in the world, Cognac, is a grape brandy distilled from wine made in Cognac, France, a legally delimited geographical area. Many other areas, regions, and countries make famous brandies. Armagnac is another famous French grape brandy, Grappa is an Italian grape brandy, Calvados is a French apple brandy, Kirsch is cherry brandy, Slivowitz is a plum brandy.
Whisky - A beverage distilled from a mash of grain. As brandy is distilled from a wine, whisky is distilled from what is basically a beer. In fact, the fermented liquid is called distillers beer. The types of grains used, the quality and type of water, the method of distillation, the proof of distillation, the length of maturation, the type of wood used in aging will all contribute to the quality and type of whisky.
Vodka – Usually distilled from a mash made by fermenting a grain mixture although other substances are used such as potatoes and sugar cane. When distilled from a grain mash, it is similar to whisky, but, while a whisky has a distinctive color, odor, and flavor, vodka processing is directed towards elimination of those characteristics. This is done by skillful distillation at high proof and by post- distillation processing techniques.
Rum - Distilled from a spirituous liquid made by fermenting sugar cane and/or molasses.
Tequila - The distillate of the fermented juice of the mezcal variety of the Agave plant. As wine is the precursor of brandy, and beer is the precursor of whisky and vodka, pulque is the precursor of Tequila.
Neutral Spirits - When alcohol containing liquids are distilled at very high proofs (95% alcohol or higher), the resulting distillate is nearly pure alcohol and has little if any distinctive character, hence the term "neutral" spirits. Neutral spirits are nearly always produced from a fermented grain mixture. In this case, the correct term is neutral grain spirits.
Fermented and Distilled Alcoholic Beverages - Compounded Spirits. Definitions
Gin - A juniper flavored spirit obtained by the distillation and rectification of the grain spirits of malted barley and rye, or sometimes corn and maize.
Cordials/Liqueurs - Neutral spirits, brandy, whisky or other distilled spirits mixed or redistilled with fruits, flavors, plants, or other natural flavoring agents, or extracts derived from such materials. U.S. law states that they must contain a minimum of 2.5% of sugar (by finished weight).
Summary: Origins of Spirits
Cactus: (and related plants)
Alcoholic fermentation is the anaerobic (living and producing in the absence of atmospheric oxygen) conversion of sugar into carbon dioxide and ethyl alcohol in the presence of yeasts. The term fermentation is used in three ways with alcoholic beverages: primary fermentation, secondary fermentation, and malolactic fermentation. Primary fermentation is alcoholic fermentation as defined above. Secondary fermentation describes the same chemical reaction, but it refers to its employment for specialized products. Sparkling wines undergo a secondary fermentation in closed containers thereby retaining the carbon dioxide. Beers may also have a secondary fermentation and the purpose is the same; retention of carbon dioxide to produce a carbonated beverage. Malolactic fermentation, on the other hand, is not an alcoholic fermentation at all. It describes the conversion of malic acid to lactic acid and is an important reaction for some wines. We are concerned here with alcoholic fermentation.
Chemistry Of Fermentation
Although alcoholic beverages have been known to mankind for virtually their entire recorded history, it is only relatively recently that we have understood what occurs during the fermentation process. The first attempt at a scientific explanation came from George Ernest Stahl, born in Germany in 1660, in his book "Zymotechnica Fundamentalis". While his theories seem rather bizarre today, they were widely accepted during the eighteenth century.
The French chemist, Lavoisier (1743-1794), was the first to show that, by the process of fermentation, sugar was transformed into alcohol and carbon dioxide. Another Frenchman, Latour, was the first (1837) to describe yeast as the organism producing the alcoholic fermentation although he thought yeast was a vegetable organism. Knetzing and Turpin, in 1838, claimed that yeasts were animated organisms, causing fermentation through their own living development. Their theory was disregarded by most of their peers at the time, and it was left to Louis Pasteur, from 1857 on, to show that yeast was a living organism and that fermentation was only possible with live yeasts.
In 1810, the French scientist, Gay-Lussac, reported the famous equation describing the overall reaction: C6H1206 -----> 2 C2H5OH + 2 CO2. Pasteur was able to confirm its overall validity but he also showed the presence of several unaccounted for by- products such as glycerol, lactic acid, acetaldehyde, and acetic acid. It is now known that there are a complex series of chain reactions, beginning with glucose and ending with ethanol and carbon dioxide and that the yeasts themselves do not cause the reactions but instead, provide various enzymes which catalyze or speed up the rate of the reactions. The actual conversion takes places in a series of steps, each one controlled by specific enzymes & other necessary materials, such as metal ions.
Since alcoholic fermentation is an anaerobic process, it does not require air. The presence of air would, in fact, slow down or eliminate the production of alcohol. Whatever air is trapped in the fermenting liquid would be consumed during the rapid multiplication of yeast cells in the beginning of fermentation. Escaping carbon dioxide during the latter stages also aids in preventing access to air and oxygen.
If air & oxygen were available, the fermentation would become aerobic, and as stated, would reduce or eliminate alcohol as an end product. This is due to the very considerable difference in energy released during the two types of fermentations. Both aerobic and anaerobic fermentations are exothermic, that is, they give off heat. During alcoholic (anaerobic) fermentation, consumption of one molecule of sugar will result in a change of 56 kilocalories of energy. Aerobic fermentation will release 673 kilocalories of energy, a nearly twelvefold increase. This causes a significant difference in what takes place during the fermentation. The energy released is required by the yeasts for their metabolism; their reproduction. In anaerobic fermentation, since relatively little of the potential energy is released, the reduction in available energy means that the yeasts have to work hard at converting sugar into alcohol, not at reproducing. During aerobic fermentation however, there is great efficiency in energy production from the consumption of sugar and it fuels increased yeast growth, at the expense of alcohol. Most of the sugar is, in fact, consumed to aid yeast cells in their building and reproduction processes. This is why, when brewers, winemakers and distillers (or other food producers) want to grow yeasts, as opposed to producing alcohol, they grow them aerobically.
The equation for alcoholic fermentation can thus be re-stated as follows:
C6H12O6 ------------------> 2 C2H5OH + 2 CO2 + 56 kcal energy
This can be written as: one molecule of sugar, catalyzed by yeast enzymes produces two molecules of ethanol, 2 molecules of carbon dioxide, and 56 kilocalories of energy.
Since the primary purpose of fermentation is to produce alcohol, the alcoholic beverage processor is very interested in how much alcohol can be produced. The theoretical yield is 51.1% ethanol and 48.9% carbon dioxide although the actual yields are only about 90-95% of the theoretical. Among the reasons for this are: the amount and kinds of by-products produced, the amount of sugar used by the yeasts, the proportion of sugar used to synthesize new yeasts, the amount of sugar used by other microorganisms, the rate and temperature of fermentation, the air available (there will always be some amount of aerobic fermentation activity), agitation of the fermenting mass, alcohol loss due to volatilization, and the variety and maturation of the grapes (in winemaking). The formula used by most winemakers is: one degree Brix =.535% alcohol by volume. Brix is a measurement of solids in solution and in practice is assumed to be sugar. Thus, a grape mixture with a Brix or sugar content of 20% would produce a wine with an alcoholic content of 10.7% by volume.
Although ethanol is the primary alcohol produced, it is not the only one. Higher alcohols, known as "fusel oils", are also products of alcoholic fermentation and, while they are present only in minute amounts, they are very important to the quality and distinctiveness of the final product. These are alcohols with more than the two carbon atoms of ethanol. Some of the more common ones are: propanol (3 carbons), butanol (4 carbons), and amyl alcohol (5 carbons). Methanol, or wood alcohol, has only one carbon atom, and is considered not to be produced by alcoholic fermentation. It can however be derived from the hydrolysis of pectin and is normally present in wines in very minute amounts.
Importance Of Yeasts And Use Of Yeasts
The function of the yeasts, as pointed out, is to provide suitable enzymes which in turn will catalyze the desired series of chain reactions. Because the grape skins will be populated with wild yeasts, a fermentation can proceed naturally; all that has to be done is to gather and crush the grapes. The naturally occurring yeasts will cause a fermentation. This is how wine undoubtedly first was made, and it must have been discovered accidentally. Leaving the fermentation to nature however may not necessarily be the best thing to do. All yeasts are not equal when it comes to alcoholic fermentation; some are much more desirable than others while some are quite definitely undesirable. The winemaker sacrifices a great deal of control by not specifying particular yeast types and risks the success of the winemaking process.
European winemakers make wide use of natural yeast fermentations. Some consider the naturally occurring yeasts to be a critical quality factor. In comparing this with U.S. winemaking procedures, it must be remembered that vineyard areas in Europe have been established by trial and error over hundreds of years; a thousand or more in some instances. Europeans produce only a limited range of wine types, often only one, in sometimes large vineyard areas. Trial and error have shown them which grapes and wine types are best suited for each particular set of geographical and climatological conditions. The presence of specific strains of wild yeasts are most definitely an important part of these conditions. European vineyard areas also tend to be more consistent from a climate standpoint from mile to mile than do those of California for instance. An entire European region such as Beaujolais grows basically only one grape and makes one type of wine, while in the Napa Valley a very broad range of wine types are made from an equally broad range of grape varieties. It is not realistic to assume that wild yeast populations would be equally suitable for all these wines.
Another factor of importance is that California grapes do not have as reliable or as good a source of wild yeast populations as do European grapes. Research has shown the presence, in California, of many types of yeasts on grapes, not all of which are suitable for wine fermentations. This is hardly surprising since these grape varieties originated in Europe. The most desirable yeast is Saccharomyces Cerevisiae and they may not even be a part of the population. Even when they do appear, they are outnumbered by unwanted microorganisms. A major problem with wild yeasts is their unpredictability; another is their tendency to multiply and become dominant very quickly. Wild/natural yeast fermentations can result in stuck (unfinished) fermentations, and the formation of unpleasant odors. Saccharomyces Cerevisiae, of which a great variety of strains exist, has a high reproduction rate, fermentation efficiency is high, and can tolerate relatively high alcohol levels (15-16%). As pointed out, a fermentation efficiency of 95% is possible (95% of the potential alcohol is produced). This is with S. Cerevisiae, with wild yeasts side reactions could consume much of the sugar, at the expense of alcohol production.
Beer production and the fermentation of alcoholic beverages for distillation purposes require the use of specially prepared yeast cultures; they cannot depend on the presence of wild yeasts. Beer and spirit manufacturers also use strains of S. Cerevisiae for their fermentations. There is one beer, however, the famous Lambic of Belgium, that still uses wild yeasts (and other microorganisms) for fermentation.
The University of California at Davis long ago began the preparation of pure wine yeast cultures for starting fermentations. In the 1960's, the Montrachet strain was the most popular type. In the 1970's there was a great deal of research and experimentation with other strains in order to reduce volatile acidity, eliminate undesirable odors, find out what the differences in wine aromas were, and to gain increased control over the fermentation. Specific strains have been isolated to perform particular kinds of fermentations. Examples would be: slow, fast, low temperature, high alcohol, and development of distinctive flavors.
It should be obvious that fermentation is a very complex series of chemical reactions. Much is now known about what happens and why and the alcoholic beverage producer can exercise a great deal of control over the process. We will discuss here some of the major ways in which the winemaker or distilled beverage producer can control the fermentation process and the type of beverage made.
Yeast Strains.-There are countless strains of yeasts which can be used. Each will have its own specific effect on the character of the finished beverage as well as on the fermentation process itself. It is not as simple as merely mixing some yeast into the liquid to be fermented, be it fruit juice, a grain/water mixture, or whatever. Winemakers strive to produce particular types of wines and will select the yeasts with care. Red wines, white wines, sparkling wines, sauternes or beerenauslesen type sweet wines, high alcohol wines, and low alcohol wines are just a few examples of products calling for different approaches in yeast selection.
Fermentation temperature is of critical importance today in winemaking and proper selection of yeasts is necessary for control. Research has shown that various strains of Saccharomyces Cerevisiae vary considerably in their ability to carry out fermentations at different temperatures. Some are highly efficient at low temperatures but will not produce adequate amounts of alcohol at high ones while, with other strains, the reverse is true.
Temperature.-Yeasts, like all living organisms, have specific temperature requirements. If the temperature is too high or too low, they will cease to function. Wine yeasts ferment effectively over a temperature range of 50-90oF./10-32oC. If the temperature exceeds 100oF./38oC., the yeasts may die, resulting in what is called a "stuck" or incomplete fermentation. It can be very difficult to restart and complete the fermentation when this occurs. Other problems with excessive temperatures are: encouragement of microbial spoilage, increased loss of alcohol and other volatiles due to evaporation, and increased formation of undesirable by-products.
In spirit making, the fermentation temperature should not be allowed to exceed 90oF./32oC. If there are adequate means for cooling the fermenting mass, temperatures of 81-86oF./27-30oC. may be used. If there are no cooling facilities, it is recommended to start the fermentation at no higher than 70oF./21oC.
White wines today are fermented at relatively low temperatures, 50-60oF/10-16oC. although specific types may vary considerably. The wines are fresher, fruitier, and have greater delicacy. There is also less bacterial and wild yeast activity, higher alcohol yield, and reduced loss of volatile aromatics.
Red wines are fermented at much higher temperatures than are whites, mainly because of the necessity for color extraction from the skins. The temperature range for red wine fermentation is from 70oF. to about 82oF. (21-28oC)
During red wine fermentation, the carbon dioxide attaches to the skins and other solids and is carried to the surface where it forms a "cap", a dense formation of solid material. Temperature increases due to the cap can be as much as 50oF./10oC. and therefore have to be controlled. This is done by physically breaking up the cap by frequent pumping of the must from the bottom of the tank over the cap. The traditional European method was to break it up by "punching" it with hands, boards, or whatever was available. It was not unknown for people to strip and jump in although it is unlikely this procedure is followed today. Because of this heat build-up and the subsequent punching, red wines were fermented in smaller containers than were whites.
With beers, there are two basic yeast types; bottom fermenting yeasts that operate at temperatures from 45-60O F. and produce lager beers, and top fermenting yeasts that operate at higher temperatures (60-700 F.) and produce ales. Because of the fermentation temperature differences and the differences between the sensory characteristics of the two types of beers, ales are often compared to red wines and lagers to white wines.
Time.-The fermentation time is a factor of the temperature. White wines, fermented at lower temperatures will naturally take longer; how much longer depends on how low the temperature is. An ideal for white wines is said to be when the sugar is converted at the rate of 1o Brix per day, or for a total of from 15-25 days. Red wines will typically ferment to dryness (no remaining fermentable sugars) in about a week.
Choice Of Materials For Fermenters.
Fermentation was traditionally done in open wooden containers and the temperature was whatever the ambient temperature of the environment was. The time was dependent on what the temperature was. As a result, the winemaker did not have a lot of control over what was going on and this would in turn lead to great variations in the wines from year to year. Champagne is said to have been accidentally discovered due to unexpected temperature fluctuations. One year, the temperature cooled unusually quickly and stopped the fermentation. Thinking the wine was finished, the winemakers bottled it and, in the spring, when it again warmed up, the fermentation began anew. Sparkling wine was born, probably at the expense of many exploding bottles!
In order to ferment white wines at low temperature, it is necessary to have some sort of temperature controlled fermenting facility. Water jacketed fermenters made from stainless steel are widely used for this purpose and they can be adjusted for whatever temperature is wanted. Some white wines, notably barrel fermented Chardonnays, will still be fermented in open wooden containers at higher temperatures than usual for white wines today. In such cases the winemakers will start with musts which have higher solids contents and they will typically use Montrachet and Champagne yeast strains. Their objective is to attain the greater complexity which results from the wood contact, increased air contact, and the higher temperature. The wine will be less fruity but richer tasting and heavier in body. The process is more difficult to control, it is easier for problems to arise, and is more demanding as regards the winemakers skill.
Residual Sugar.-Not all wines are fermented dry. A dry wine is the result of a complete fermentation; that is, all the fermentable sugar has been consumed during the process. Many wines are intended to have varying degrees of sweetness to them, from barely perceptible sweetness to very sweet. The sugar remaining in the finished wine is termed residual sugar.
There were two traditional methods of producing these types of wines. With one, the winemaker added sweet concentrated grape juice to the dry, completely fermented, wine. The juice was concentrated by water removal and could have a sugar content of as much as 60%.
The other method involved the use of a sweet reserve. This is a German technique and calls for sweetening the dry wine with sweet juice (not concentrated). With today's refrigerated equipment the process is both more simple and natural. By lowering the temperature, the fermentation is stopped before all the sugar is consumed. The result is sugar in the finished wine. The yeasts are then removed by filtration, centrifuging, or natural settling. This is now the method most used in California. This technique is not suitable for all viticultural areas however since there must be sufficient sugar in the grapes to provide for adequate alcohol at the time the fermentation is stopped. Many cool growing areas, such as Germany and New York State, simply do not produce grapes regularly with sufficient natural sugar to do this. They may have insufficient alcohol even when the fermentation proceeds to its conclusion.
Sulfur Dioxide.-Sulfur dioxide (SO2) is universally used to control alcoholic fermentations. It inhibits wild, undesirable yeasts without interfering with the activity of Saccharomyces Cerevisiae. It also acts as an anti-oxidant, selectively reacting with oxygen so that the oxygen is not available to cause browning reactions in the musts and to promote aerobic fermentation.
What Is Distillation?
Distillation is a separation process; the ethyl alcohol is removed or separated from the fermented beverage. This is done by taking advantage of the different boiling points of the main constituents of fermented beverages, water and alcohol. Water vaporizes (turns from a liquid into a gas) at 212oF. while ethyl alcohol changes at 173oF. Therefore, if a spirituous liquid is heated to below the boiling point of water, the alcohol can be selectively vaporized. For example, a wine of 10 percent alcohol boils at 199O F. If this vapor is collected and cooled, it will turn back into a liquid consisting mostly of alcohol. As we have seen, the fermentation ingredients determine the classification of the spirit. If alcohol is distilled from wine, the spirit is brandy, if it is distilled from beer, the product is whisky, if it is distilled from a sugar cane fermented beverage, the spirit is rum, and so forth.
Technically, if a distillation is performed on an already distilled substance, or on one in which all components have the same boiling point, it is termed rectification. A rectified spirit is one which has undergone purification by distillation at a licensed rectifier's premises. From a practical standpoint, there is in the United States a rectification tax which is levied on any process which changes the character of the spirit. Examples of such practices are given in Table 1.2.
What is Proof?.-The term is used to describe alcoholic strength and has an interesting origin. Prior to the development of alcohol measuring instruments, the strength of the newly distilled spirit was determined as follows. The spirit was mixed equally with gunpowder and lighted. If it was too strong or too weak, it either burned too fast or not at all. When it was of a proper strength, it burned evenly, with a blue flame, and the spirit was said to have been "proved". This was later found to be about 50% alcohol.
Thus the term 100 proof was used to describe a beverage with 50% alcohol. A liquid of pure alcohol would thus be 200 proof. This is the American system of alcoholic content labeling; proof divided by half equals the alcohol percentage by volume. The British also use proof, but use it differently. 100 British proof equals 57.1% ethanol by volume. The French use a system called Gay-Lussac which describes the alcohol percentage by degrees Gay-Lussac. A spirit with 40% alcohol by volume would be 40o G.L. Most of the rest of the world uses percentage by volume.
Three Uses Of Proof.-It can be used to describe the alcoholic content at three different stages in the life of the spirit. One would be the proof at time of distillation, another would be the proof of the spirit to be aged, and the third would be bottling proof. The spirit is seldom aged at the same proof at which it comes from the still. It could, for example, be cut with water prior to being placed in wood. Following wood aging, the spirit is again cut with water to reach the commercial strength, the bottled alcoholic content.
For example, a spirit could be distilled at 150 proof (75% alcohol), cut with water to 125 proof (62.5% alcohol) for wood aging, and 4 years later cut again with water to 80 proof (40% alcohol) prior to bottling. The bottling proof is usually a marketing/economic decision although there are Federal regulations in some cases. Bottled in Bond is one; the requirement is for 100 proof. The aging proof may be regulated, either by legal stipulation or by tradition. The distillation proof, however, is of critical importance and is carefully specified by law with virtually all products in all countries.
Relationship Between Distillation Proof and Product Character.- The differences among spirits are in the non-ethyl alcohol portion of the distillate. To paraphrase Gertrude Stein: ethyl alcohol is ethyl alcohol is ethyl alcohol. If a spirit were distilled at 200 proof, there would be absolutely no difference among products obtained from a wine distillation, a distillation of grain mash, of rice, of sugar cane, or even from a distillation performed in a laboratory. Other constituents are however also removed along with alcohol during the distillation.
If a spirit were distilled at 150 proof, it would contain 75% alcohol and 25% congeners. Such a spirit would have considerably more potential character in the way of distinctive flavor, aroma, and body than would the 200 proof spirit. It would not, however, have the flavor/aroma potential of a spirit distilled at 120 proof; 60% alcohol and 40% congeners.
Specific types of products must be distilled at particular proofs if they are to be typical examples of that type. Vodka, for example, is not expected to show any distinctive flavor or aromatic characteristics and is expected to be light-bodied. It is made from spirits distilled at as high a proof as possible and then further processed to remove whatever congeneric compounds remain. In fact, anything over 190 proof is legally termed "neutral" spirits because it has no distinctive characteristics other than those attributed to alcohol. Bourbon, which is certainly much more flavorful and aromatic, and has more body than does Vodka, cannot be distilled at over 160 proof. Cognac cannot be distilled at over 144 proof; in practice, the average is 140. California brandy, which is typically much lighter than Cognac brandies, has a legal distillation maximum of 170 proof. Light rums are distilled at 180-190 proof. Scotch malt whisky is distilled at 140-142 proof while the lighter Canadian whisky is distilled out at varying strengths ranging from 140-180 (or higher) proof.
Components of Distilled Spirits
Since most spirits are bottled at under 100 proof, the primary component is usually water. Whatever water is not provided by the distillation is added when cutting to aging and bottling strength. Distilled water is used to avoid any flavor/aroma problems. The other major component is, of course, ethanol.
The congeners, those secondary products produced during alcoholic fermentation, consist of acids, esters, aldehydes, fusel oils, extracts of mineral salts, and solids in minute quantities. Collectively, they do not amount to much from a percentage standpoint, but they are the determining factors as regards product character. They come from the fermentation ingredients, and are by-products of the fermentation reactions, as well as from the distillation and aging processes. Aging is of great importance in the case of wood-aged spirits since substantial flavors, odors, and textures are extracted from the wood.
Esters are volatile substances which give aroma to the spirits; their capture during distillation is very important. Aldehydes are produced from alcohol/air reactions and contribute to the character of the spirit. The formidable sounding fusel oils are actually alcohols containing more than the two carbon atoms of ethyl alcohol. They are called higher alcohols and form complex mixtures which add significantly to spirits. Not all these compounds are desirable, and even those which are, should be present in specific amounts. This requires proper equipment and skillful manipulation of that equipment on the part of the distiller.
Pot Stills (Batch Processing)
The original, and least complex, distillation apparatus is a pot still. It is a batch processing method, not a continuous one. That is, it can only process one load, or batch of fermented liquid at a time. There are stills which operate continuously; as long as a spirituous liquid is fed in one end, a distilled spirit will come out of the other end. These types of stills will be described in the next section. The pot still consists of, in its most elemental form, a receptacle into which the liquid can be placed and heated. There will be some sort of long, tapered neck attached at the top to collect the vapors which are formed when the liquid is heated. A spiral copper tube will be attached to this neck and will pass through a cooling medium, usually water. The decrease in temperature will condense the vapor to a liquid again.
The product is a distilled spirit, but it is not necessarily a finished product. Cognac, for instance, is the result of a double distillation, and Irish whiskey was traditionally given a triple distillation. Highly volatile elements, which will vaporize first, can be collected separately, as can the least volatile elements since they vaporize last. In Cognac distillation, the highly volatile fraction is called the "headings" and the least volatile, the "tailings". The middle distillate is the one which contains the most alcohol and it is given the second distillation. The headings and tailings are again separated during the second distillation and the middle portion becomes Cognac.
Pot stills are thought by many to produce a better and more flavorful product and are used for most of the world's finest spirits. Cognac, Armagnac, and the better Calvados brandies are all pot-distilled, as is Malt Scotch whisky, most Irish whiskey, and some rums and liqueurs. Pot stills generally distill at 65-70% alcohol (second distillation, the first is much lower) and this is close to the optimum for fusel oil extraction while continuous stills generally draw off the spirits at higher proofs. Fusel oil concentrations are thus likely to be higher with pot distillation. Esters are concentrated at a level slightly below fusel oils and are drawn off quickly in the "heads" fraction. The challenge for the distiller is to include enough of them in the middle distillate without including undesirable odorous elements from the heads fraction. The least volatile elements, those in the "tails" portion, are undesirable since they are low in ethanol and contain heavy, unsuitable flavors & odors. They can, however, be re-distilled to recover whatever ethanol they do contain.
Continuous Stills (Continuous Processing)
These types of stills will produce a distilled spirit continuously so long as they are supplied with a spirituous liquid. The first one was invented by Scotsman Robert Stein in 1826, and the design was perfected and patented by Aeneas Coffey, Inspector General of Excise in Ireland, in 1830. The most common name for the apparatus today is Coffey still, but the terms "patent", "tower", "column", and "continuous" may be used as well. A very important innovation, relative to the pot still, was the ability of the continuous still to separate the many vapor fractions. The removal of ethanol from what is basically a water alcohol mixture is the basic objective of distillation, but there are many other valuable fractions as we have seen. The main advantage, of course, was speed and increased productivity. The apparatus does not have to be emptied and cleaned between batches as does a pot still.
It is not possible, except in a laboratory, to distill at 200 proof and commercial distillation usually does not exceeds 192 proof. At that proof the distillate contains 96% alcohol and up to 4% of the congeneric compounds. These came from the original ingredients as well as from the fermentation reaction, and the wood, if used for aging. They provide whatever distinctiveness the product contains, and at 4%, there would be little, if any.
A simplified description of the apparatus is as follows: The alcohol-containing liquid is pumped into the top of a tall column or tower called a "rectifier". The liquid is carried down to the bottom of the column in twisting pipes. As it descends, hot vapors rising through the column warm the alcoholic liquid. This warm liquid is now pumped to the top of a second column, the "analyzer". This column is separated from top to bottom by a series of perforated plates. As the hot liquid enters at the top it drains through the top plate onto the one below and so on until it reaches the bottom. Steam, entering from the bottom, causes vaporization of the volatile elements of the liquid as it travels down through the column. Only the water and least volatile elements reach the bottom and they are drained away. The vapors are drawn off at the top and sent back to the first column, the "rectifier".
These vapors enter the rectifier at the bottom and rise, they are in fact the hot vapors which are used to first warm the incoming liquid. As the hot vapors warm the liquid, the liquid will cool the vapors. The result is that the vapor condenses back into a liquid. Depending on the height at which this occurs, distillates of varying strength can be drawn off. At relatively lower heights, the less volatile elements will condense, while at higher levels, the more volatile fractions will turn back into a liquid.
In this manner, the distiller can exercise great control over the process and the distilling proof. Since fusel oils are best extracted at alcohol levels of 65%, the high-proof spirits distilled at 85-95%, and the neutral spirits at 95%+, will not have many. Bourbon, distilled at 70-80%, will have a significant fusel oil content. The least volatile elements tend to fall to the lowest part of the column and can easily be avoided.
This more or less describes the original Coffey still and affords an understanding of how continuous distillation works. There are many different distillation processes available and the three most commonly used in the United States are: a continuous whisky separating column, with or without an auxiliary unit for the production of straight whiskies, a continuous multi-column system used for the production of neutral grain spirits, and a batch rectifying column and kettle unit, used primarily for the production of neutral spirits that are to be wood aged. The second one, the continuous multi-column unit, is quite complex. It consists of a whisky separating column, a selective distillation column, a product concentrating column, an aldehyde concentrating column, and a fusel oil concentrating column.
What Kinds Of Standards Can Be Established For Alcoholic Beverages?
A standard is defined by the Oxford American Dictionary as "a thing or quality or specification by which something may be tested or measured", and as "the required level of quality". The intention of this book is to establish what the standards for alcoholic beverages are and, in those cases where there are few "required levels" of quality, what they ought to be. This will be done with each of the beverages by an examination of the following:
All alcoholic beverages provide calories since alcohol yields (pure alcohol) 7 kcal/gram and one ounce of 90 proof spirit contains about 73 kcalories. Some beverages however, also provide nutrients in the form of carbohydrates, minerals and vitamins. We do not intend to establish that alcoholic beverages are, in and of themselves, nutritional, but some do serve a supplementary role as regards nutrition.
Federal Standards of Identity
There are long-established Federal Standards of Identity for alcoholic beverages. They were originally developed after Repeal of Prohibition as part of the strict control over the alcoholic beverage industry and had two primary purposes. One was to provide a basis for assessing and collecting taxes, and the other was for consumer protection. The standards typically deal with such areas as ingredients, processing methods and techniques, alcoholic content, and aging requirements. The Federal Standards of Identity for each of the product types will be defined and discussed.
Raw Materials Used In Processing
As with food processing, the type and quality of the ingredients used for alcoholic fermentation are of critical importance. Inferior ingredients produce either inferior products, or products which are not considered as fine as others. Much of the quality differentiation among beverages is due to this factor and we will define the quality standards of the ingredients used for the various types of beverages.
Alcoholic beverages are not additive laden as many foods seem to be but additives are necessary for microbiological control during ingredient growth and fermentation, for clarification, and to enhance preservation. We will look at the accepted industry standards as well as the legal ones.
Processing Methods And Techniques
With each beverage category, we will establish the legal and accepted industry production standards as a frame of reference. Each type within the category will then be compared to those standards, showing how a variety of unique products can be produced. For example, with whisky, we will first look at how whisky is made in general. In making Bourbon, Scotch, Canadian, Irish, and Blended whiskies however, specific alterations are made during the processing and the standards for these variations will be explained.