Production of American whiskies: bourbon, corn, rye and Tennessee 211

Chapter 14

Production of American whiskies: bourbon, corn, ryeand TennesseeR. RalphRon Ralph & Associates Inc., Louisville, Kentucky, USA

Introduction: definitions of bourbon,corn, rye, wheat, and Tennesseewhiskies

The US Bureau of Alcohol, Tobacco and Firearms(BATF) has set specific guidelines to define alltypes of alcoholic beverages produced in theUnited States. The general definition of whiskyis �a spirit aged in wood, obtained from thedistillation of a fermented mash of grain.� Thisspirit can be produced from any grain orcombination of grains; but corn, rye and maltedbarley are the principle grains used. Whisky isan alcohol distillate from a fermented mashproduced at less than 190o proof in such amanner that the distillate possesses the taste,aroma and characteristics generally attributed towhisky; stored in an oak container, and bottledat not less than 80o proof. Also, whisky maycontain mixtures of other distillates for which nospecific standards of identity are noted.

Bourbon, rye, wheat whiskies are produced(distilled) at a proof no higher than 160o from afermented mash of not less that 51% corn, ryeor wheat and aged in new, charred oak barrelsat a proof no greater than 125o. Also, thesewhiskies may include mixtures of whiskies of thesame type. Corn whisky differs in that it may be

aged in used or uncharred new oak barrels. Also,corn whisky may include a mixture of otherwhiskies. Tennessee whisky has the samedefinition of all four whisky types, but to belabeled �Tennessee� it must be produced andaged in wood in the state of Tennessee.

All whiskies conforming to Section 5.22 ofthe BATF regulations must be aged a minimumof two years. To be designated a �straight� whisky,it must conform to all regulations for its type andbe aged not less than two years. �Light� whiskyis another type of whisky produced in the US. Itis distilled at more than 160o but less than 190o

proof and aged at least two years in used oruncharred new oak barrels.

In the US regulations, neutral spirits, vodka,Scotch whisky, Irish whiskey, and Canadianwhisky are further defined. Neutral spirits aredistilled spirits produced from any materialdistilled at or above 190o proof and bottled atnot less than 80o proof. Vodka is a neutral spiritdistilled and treated with charcoal or othermaterials to be without distinctive character,aroma, taste or color. Scotch, Irish and Canadianwhiskies are defined as �distinctive products ofScotland, Ireland, and Canada, respectively, andproduced and distilled under the laws of thosecountries�.

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History of North American whiskyproduction

Whisky production began in the US in 1733when the British government passed theMolasses Act. Until that time, the colonistsproduced distilled spirits from molasses. TheMolasses Act imposed a duty on molasses ofnon-British origin. Since the American colonistsimported most of their molasses from the Frenchand Spanish islands, they were greatly concerned.Since non-British molasses was cheaper andmore abundant, smuggling and ignoring theMolasses Act (and the later Sugar Act) was thebasis for much of the �Spirit of �76�.

Pre-revolution grain whisky production wassmall; although history notes that settlers inwestern Maryland and Pennsylvania producedrye whisky from their abundant rye grain cropsand that rye whisky began to replace the popularmolasses-based rums. After the Revolution, theEmbargo Act cut off the supply of molasses; andwith abolition of the slave trade by the newCongress, both molasses and slaves weresmuggled into the US. These events increasedthe cost of molasses and accelerated the declineof rum.

The westward migration

Early settlers crossing the Allegheny Mountainsincluded many Scots and Irish immigrants whowere grain farmers and distillers with knowledgeof pot still operation from their homelands. Theyproduced the rye whisky that became the first�American� whisky. When Alexander Hamiltonneeded money to pay the debts incurred duringthe American Revolution, he pushed an excisetax levied on distilled spirits through Congress.As news of the tax spread, the uproar and publicoutrage was so intense that PresidentWashington sent 13,000 troops into westernPennsylvania to quell the �Whisky Rebellion�. Asthe troops entered from the east, many farmer-distillers packed their stills and headed west toKentucky to avoid both the tax and the army.

The farmers found Kentucky soils not assuitable for rye and wheat crops as soils inPennsylvania and Maryland. They discoveredthat corn was much easier to cultivate. The firstwriting that expounded on corn growing inKentucky comes from the Jesuit HierosmLalemont. He noted �to mention the Indian Cornonly, it puts forth a stalk of such extraordinarythickness and height that one could take it for atree, while it bears ears two feet long with grainsthat resemble in size our large Muscatel grapes�(Carson, 1963).

Whisky production grew rapidly in the earlyfrontier areas as the settlers found in whisky ameans of moving grain to market. A pack horsecould carry only four bushels of corn, rye orwheat; but that same horse could carry 24bushels of grain that had been mashed anddistilled into two kegs of whisky. Also, the priceof whisky was more than double the price thefarmer could get for grain.

Bourbon�s �accidental� history

As settlements moved westward, the demandfor spirits increased. Riverboats had become ameans for shipping barrelled whiskies to theirdestinations. A version of �bourbon history�recounts how a Baptist minister, Elijah Craig,burned or �charred� the inside of fish barrels torid them of the fishy smell so he could fill thebarrels with whisky to be shipped by raft downthe Mississippi River to New Orleans. The whiskyfrom the charred oak barrels �aged� duringshipping and storage. This aging improved thecharacter of the whisky, gave it color andsmoothed the taste (Carson, 1963).

Another version of this history tells of acareless cooper who accidentally let the stavescatch fire (char) when heating them for pliabilityto make into barrels. Not wanting to losemoney, he did not tell his distiller customer aboutthe charred staves in the barrels. Months later,after the distiller filled the barrels and shippedthe whisky downriver, the distiller heard pleasingcompliments about his whisky. After discovering

Production of American whiskies: bourbon, corn, rye and Tennessee 213

the cooper�s �mistake�, the distiller asked him torepeat the charring process for all of his barrels.

Contrary to popular belief, none of this�history� occurred in Bourbon County, Kentucky,and no one really knows how bourbon whiskywas first made. The only historical evidenceindicating Bourbon County as the source ofbourbon whisky comes from a 1787 indictmentof James Garrad (later a Kentucky governor) andtwo others by a Bourbon County grand jury forretailing liquor without a license. The onlycertainty in any of the lore is that Kentucky has acounty named Bourbon and produces a whiskyby the same name (Connelley and Coulter,1922).

Essential traditions

Despite uncertainty about origins of the bourbonname, a tradition of good whisky making washanded down from fathers to sons forgenerations. Formulas, mash bills, yeastingmethods and skills for operating the stills werepassed along, even though many farmer-distillerscould not read or write. They did not knowacrolein from fusel oil, but they did have thespecial knack for making the �cuts�. They knewgood, clean yellow corn and plump rye. Theyfaithfully guarded their yeast and yeast methodsthough many could not have said whether yeastbelonged to the animal or vegetable kingdoms.Two exceptional bourbon whiskies of the 19thcentury were Old Taylor and Old Crow. OldOverholt was reportedly the best of the ryewhiskies.

During the 19th century, the pot still evolvedinto the continuous column �beer still� with adoubler or thumper. The continuous stilloperations allowed distillers to move to largerfermenters, more and larger cookers andautomated grain handling. As the distilleryoperations grew and became increasinglyautomated, some of the smaller distilleries fellby the wayside or promoted their brands asbetter as a result of their �old time, small distillerytradition and quality�. They touted this tradition

and sold it as part of the product. The well knownMaker�s Mark bourbon is a prime example oftradition and sound practice bottled andsuccessfully marketed to modern consumers.

As grain whisky and bourbon productiongrew in the 19th century, the US governmentincreased the excise tax and the number ofregulations. Costs passed on to the consumersdampened their enthusiasm for drink; butgovernment regulation incensed leaders of theTemperance Movement because the tax andregulations drew attention to the production andsales of liquor. Most whisky at that time wassold �from the barrel�, and quality standards werealmost nonexistent. It was not until the end ofthe century that consumers could purchasewhisky sold in a corked and sealed bottle. OldForester was the first product with �guaranteedquality� put on the label. Old Heritage was thefirst bourbon with a strip stamp over the cork,thereby becoming the first �bottled-in-bond�bourbon.

The prohibition era

All of the improvements in the �character� ofwhisky production and consumption were to noavail when at 12:01 a.m. on Saturday, January17, 1920 all beverages containing more than0.5% alcohol were outlawed in the US(Tennessee, the state with the first registereddistillery in the country, Jack Daniel Distillery,became the third state to vote to go dry in 1910,ten long years before the passing of the Volstead(Alcohol Prohibition) Act.) The 18th amendmentto the Constitution, which prohibited theproduction and sale of alcoholic beverages,sounded a death knell for many distilleries. Adrive through the countryside revealed closeddistilleries choked with weeds with facilities inruins. Brown-Forman Distillery in Louisville,Kentucky, was one of the few that survivedbecause it produced its Old Forester Bourbon�for medicinal purposes only�. Other distillerieslay in wait for �the experiment� of prohibition toend.

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Passage of the 21st amendment endedProhibition after 13 years. At midnight on April7, 1933 wines and beer were again legally sold;and on December 5 of that year at 5:32 p.m.bour-bon was again on the market. The Americandistilled spirits industry surged into production,building larger, more modern distilleries. Theresumed legal production and sales werereinforced by the federal government when itpassed the Federal Alcohol Control Act, whicheliminated the sale of bulk whiskies to thewholesale and retail trades. This Act also formedthe Alcohol and Tobacco Tax Division of theInternal Revenue Service. Though creating bur-eaucracy and taxation, the new Act also setregulations and definitions for producing spiritsin the United States.

Distillation�s new era

The new regulations defined the production ofbourbon, rye, corn and blended whiskies as wellas gin, brandies, rums, cordials and vodkaaccording to their spirit type. The Act also notedthe use of geographical designations with anorigin defined for Scotch, Canadian, and Irishwhiskies. This evolution of the industry led tothe organization of companies that had goals ofproducing top quality spirits within the newregulations. New companies such as NationalDistillers and Schenley joined the Americandistilleries that survived prohibition, Brown-Forman and Jim Beam, along with the Canadiandistillers, Seagrams and Hiram Walker. Thesedistillers based their production methods onprecisely defined procedures from yeasting tomaturation.

During World War II, North Americandistilleries ceased whisky production and beganmanufacturing industrial alcohol for the wareffort. Distillers gained the resources for furthertechnical improvements; and at the War�s end,the industry in the United States was technicallyready to produce better bourbons, ryes, andTennessee whiskies than ever before.

While the basis for modern American whisky

production was developed during World WarII, today�s modern American distillery operateswith recent innovations in controls (includingcomputerization) and heat reclamation as themost significant advances. Even with all of themodern technology, the US distiller still carefullycontrols his yeasts, mash bills, distillation methodsand maturation criteria, essential factors for goodquality products initiated by the early pioneerdistillers.

Production and maturationoperations

In the production of American whiskies, sixfactors determine the character and flavor foreach type of whisky:

1) Grain proportions in the mash bill2) Mashing technique3) Strain of yeast4) Fermentation environment5) Type and operation parameters of distillation

equipment6) Type of barrel used and the maturation

process

These factors were recognized and carefullycontrolled in the distilling operations of the earlysettlers (Lyons, 1981). Families and companiesthat ensured consistency and control over thesefactors remain in business today. Those whofailed to strictly adhere to a regimen controllingeach factor have fallen by the wayside.

A matter of distinction

Popular bourbon producers use specific processdifferences to make their products distinct. TheJack Daniel Distillery continues to produce itswhisky with the same processes used more than100 years ago. Their strict adherence to traditionalong with a down-home, folksy image haveproven successful marketing tools for the whisky.

Production of American whiskies: bourbon, corn, rye and Tennessee 215

At Maker�s Mark, grain selection and proportionsare used to produce a superior whisky. Theyuse wheat instead of rye in the mash bill. Thewheat and good, consistent control of all factors,especially the barrels, make Maker�s Mark thesmoothest of the bourbons. Their claim of�handmade� is justified because of their intenseattention to production parameters.

All American whiskies maintain standards forthe six production factors; and the variationsamong distilleries in adherence to standards forthese factors determine flavor and costdifferences. All American distillers start with acareful grain purchasing program. Though priceis a criterion, they all use #1 or #2 yellow corn,#1 plump northern rye, and choice northernmalted barley. Any off odors or below-grade

grain are rejected at the distillery. Very stringentgrain standards are a common feature of allAmerican distilleries (Table 1).

Mash bill

The mash bill may vary, with a typical bourbonhaving a mash bill of 70% corn, 15% rye and15% malt. A typical Tennessee whisky may have80% corn, 10% rye and 10% malt while a typicalrye whisky will have a mash bill of 51% rye, 39%corn and 10% malt. All grains are ground, withthe hammer mill being the most common typeof processing; however some roller and attritionmills are still in use. The milling (Figure 1) ischecked for grind by a sieve analysis. A typical

Table 1. Specifications and analyses of corn, rye, wheat and malt.

Specification Typical analysis

Corn (#2 recleaned)Grain odor No musty, sour or off odor �Meets spec�Moisture, % 14.0 (maximum) 12-14Cracked grains and foreign material, % 2.0 (maximum) 1-2Damaged kernels, % 3.0 (maximum) 0-1.5Heat-damaged kernels, % 0.2 (maximum) 0-0.1Bushel weight, lbs 55.0 (minimum) 55-60

Rye (#1 plump)Odor None �Meets spec�Moisture, % 14.0 (maximum) 10-14Thins, % 2.0 (maximum) 1-2Dockage, % 2.0 (maximum) 1-2Bushel weight, % 56.0 (minimum) 56-60

MaltBushel weight, lbs 35.0 (minimum) 35-38Moisture, % 6.0 (maximum) 4-6"-amylase 60.0 (minimum) 60-64Diastatic power 22.0 (minimum) 22-26Bacteria count, CFU/g 1,000,000.0 (maximum) 400-500,000

WheatOdor None �Meets spec�Moisture, % 14.0 (maximum) 10-14Thins, % 2.0 (maximum) 1-2Dockage, % 2.0 (maximum) 1-2Bushel weight, lbs 56.0 (minimum) 56-60

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sieve analysis for grains in a bourbon mash bill isshown in Table 2.

Mashing

Mashing techniques vary considerably, but themajor difference is whether pressure oratmospheric batch cooking is used. Bourbon,rye, wheat, Tennessee and corn whisky aremashed using batch cookers. Only the �blend�or �light� whisky producers use continuouscookers. Pressure cooking is usually done at124oC while atmospheric cooks are done at100oC. Cooking time varies from 15 minutes to1 hr. Conversion time and temperature are veryconsistent among distilleries. Malt is neversubjected to temperatures greater that 64oC; andconversion time is usually less that 25 minutesto minimize contamination. All distillers usebackset (centrifuged or screened stillage fromthe base of the still), but the quantity of backsetwill vary based upon the beer gallonage (gallonsof water per 56 lb distillers bushel of grain) to beused. American whiskies have beer gallonagesin the 30-40 gallon range. High energy costs forby-product recovery have encouraged somedistillers to use lower beer gallonage ratios forspirits. However, bourbon and Tennesseewhisky producers continue to use 30-40 gallonbeers. The cooling of cooked mash tofermentation temperature is achieved usingvacuum (barometric condensers) or coolingcoils.

Yeasting

All whisky producers use Saccharomycescerevisiae, however the yeasting techniques varytremendously between the �modern� and�traditional� distillers. The modern distillers haveelaborate yeast laboratories and will propagatea new yeast from an agar slant every week. Theyare very aseptic and accurate, assuring continuityof the same flavor. The �traditional� distillers useyeast stored in jugs; and though they backstockweekly, the potential for gradual yeast culturechanges and contamination can lead to flavorvariances. These distillers take extra effort andcare to ensure that their yeasting does not causeester, aldehyde or fusel oil variances in thedistillate.

The most common grains used for yeastingare small grains, rye and malted barley. Thesegrains are cooked in a separate cooker to about63oC, and the pH is adjusted to 3.8 with lacticacid bacteria grown in the yeast mash. Lacticacid production is then stopped by increasingthe temperature to 100oC for 30 minutes to killthe bacteria. This aseptic, sterile mash is thenready for the yeast from the dona tub grown inthe laboratory (Figure 2). The yeast fermentationtemperature is controlled at 27-30oC; and theyeast propagates until the Balling drops to halfthe original 22o Balling reading. This yeast mashwill have a yeast concentration of 400 millioncells/ml. Both modern and traditional distillersregularly have clean, sterile yeasts free ofbacterial contamination that may cause sidefermentations and unusual congeners in the

Table 2. Typical sieve analysis for grains in a bourbon mash bill.

US Sieve # Corn Rye Malt Wheat

16 15 22 2 2020 21 25 8 2630 17 13 14 1240 13 9 16 850 10 7 13 660 3 2 8 2Through 60 21 22 34 22

Production of American whiskies: bourbon, corn, rye and Tennessee 217

Figure 1. Typical grain-handling and milling facility.

Figure 2. Stages in yeast propagation.

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distillate. The �lactic souring� and the alcoholcontent of the finished yeast mash (8%), alongwith sterile dona and yeast tank methodscontribute to the excellent reputation Americanwhiskies have for fermentation congenerconsistency. The advantage of using small grainsare: preservation of enzymes for secondaryconversion, low steam requirements and shorterprocessing time. Also, because of its nutrientvalue, barley malt is the most importantconstituent of yeast mashes. Corn is not used ina yeast mash because it does not contain thegrowth factors required for yeast and lacticbacteria growth.

Fermentation

Fermentation is the simplest part of theproduction process, but requires more controlwith efficient equipment in order to have stable,consistent results. After the two or three cooksrequired are completed, cooled, and transferredto the fermenter, the fermenter is �set�. Settingthe fermenter means filling the fermenter withcooked mash, inoculated yeast and backset. Theyeast mash is pumped in as soon as the first cookis added to the fermenter. The addition ofbackset and/or water is done at the end of fillingto bring the fermenter to the desired final beergallonage. Most distillers use a 30-36 gallonmash, and the water:backset ratio determines theset pH. Set pH values of 4.8-5.2 are consideredto be the best starting point. The moderndistillers have closed-top fermenters with coolingcoils or external heat exchangers to controlfermentation temperature. They usually setfermenters at 27-29oC and control at 30-31oC.Traditional distillers will have metal or woodopen-top fermenters without any device tocontrol fermentation temperature. They usuallyset their fermenters as cool as they can (18-21oC)and let the fermenters work up to 31-32oC. Allof this is controlled by mash cooker cooling,addition of cold water and weather factors.Contamination is controlled by cleaningfermenters, ensuring no mash pockets in pipesand regular steaming of fermenters.

Both traditional and modern distillers fermenttheir beers for at least 72 hrs, and some for aslong as 96-120 hrs. Three and five dayfermentations are the norm. During theseperiods the Balling will drop to 0.0 and the pHfrom 5.0 to 3.8 while the alcohol concentrationrises to 8-10%. All the changes that happenduring fermentation are checked daily byperforming �beer chemistry�. Balling, pH, acids,and fermenter temperature are monitored andrecorded daily. The pH is the main indicator ofcontamination and potential fermentationproblems and is regularly measured by traditionaland modern distillers (Table 3).

Distillation

Upon completion of the fermentation process,the beer with 8.0-10.0% alcohol is transferredfrom the fermenter to the beer well. The beerwell is a holding tank for the fermented beer,such that a continuous feed to the beer still canbe maintained. Beer wells are usually 1-1.5 timesthe size of a fermenter. They also havecontinuous agitation to prevent solid grainparticles from settling to the bottom of the vessel.All American whisky producers use a continuousstill (Figure 3), though some have a seconddistillation �doubler� or �thumper� (Figure 4). Thebasic difference between a doubler and athumper is whether the unit is operated with aliquid level (doubler) or essentially dry(thumper). Both the doubler and the thumperprovide a second distillation.

The beer is pumped into the upper sectionof the first continuous column, the beer still, sixto ten plates from the top. Live steam isintroduced at the bottom. Beer stripping plates1-18 have perforations, a downcomer fromabove and a dish on the plate below to hold thebeer liquid at a set level so the plates are neverdry, as the beer moves back and forth acrosseach plate. The steam passing up and throughthe perforations, controlled by pressure or flowrate, strips the lighter, more volatile alcohol fromthe water/grain mixture on the plates. When

Production of American whiskies: bourbon, corn, rye and Tennessee 219

this alcohol gets to the top 4-8 bubble cap platesit is concentrated to about 100o proof (50o GL).As the vapors continue up into the beerpreheater (a heat exchanger to heat beer goinginto the column), some alcohol is condensedand refluxed to the top of the beer column. Therest flows to the doubler or thumper as vapor.From either of these pot still-type chambers, thevapor goes to the condenser where the productis drawn off at 130-140o proof (65-70o GL).Bourbon cannot be distilled above 160o proof(80o GL). If it comes off at more than 160o proof,it must be called �light� whisky. The stillage fromthe base of the beerstill is pumped to the dryerhouse to be processed. The �high wine� fromthe stills is pumped to the cistern room where itis held, tested and reduced to barrelling proof(Table 4).

By-product recovery

The by-product recovery does not usually receivethe same care that the other processes demand.The only essential for this process is ensuringthat the backset stays hot, around 99oC, so thatit is absolutely sterile when used in the mash tubs,yeast tubs and fermenters. (Most distillers use20-30% backset in their total process.) Further-more, the hotter the backset remains, the greaterthe savings in energy costs during the cookingprocess. The stillage from the base of the beerstill has about 7-10% total solids. When usedfor backset it is screened or centrifuged toprevent solids accumulation in the cooker andfermenters. Nearly all distillers have a dryerhouse, though a couple of traditional distillerscontinue to sell their �slop� to nearby farmers.

Table 3. Typical analysis of beers from bourbon, rye and corn whisky production.

Bourbon Rye Corn

Set sampleBalling 13.4 13.4 12.3Titratable acidity 4.5 3.6 2.8pH 4.5 5.0 5.2Temperature, oC 27.0 24.0 27.0

24 hr sampleBalling 2.6 4.0 3.6Titratable acidity 5.1 4.6 4.2pH 4.2 4.4 4.3Temperature, oC 30.0 31.0 29.0

48 hr sampleBalling 2.4 3.6 1.0Titratable acidity 7.8 7.5 6.1pH 3.8 3.9 3.8Temperature, (oC) 30.0 30.0 30.0

Drop sampleBalling 0.4 1.5 -0.4Titratable acidity 8.2 7.9 7.1pH 3.8 3.9 3.8Temperature, oC 30.0 30.0 30.0Alcohol, % by volume 6.73 5.8 6.8Residual carbohydrates, % 8.0 8.4 4.2Residual carbohydrates, % maltose 0.73 0.6 0.46

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Figure 3. Bourbon whisky still.

Table 4. Typical operating data for whisky distillations.

Bourbon Rye

Product proof 130o 130o

Still pressure (inches of water) 48 42Steam rate, lb/hr 12,000 12,000Beer feed rate, gallons/minute 120 117Reflux rate from beer preheater, gallons/hr 350 300Reflux rate from dephlegmator, gallons/hr 700 750Reflux rate from vent condenser, gallons/hr 30 65Draw-off of product, gallons/minute 12.5 10.0Still losses, % 0.0004 0.00025Water temperature to vent condenser, 0C 21 21Water temperature from dephlegmator, 0C 79 79Beer solids, % 0.06 0.06

Production of American whiskies: bourbon, corn, rye and Tennessee 221

Figure 4. Bourbon whisky distillation system, including doubler.

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Table 5. Specifications and analyses for wheat, rye and corn distillers dried grains (DDG).

Wheat and rye DDG Bourbon and corn DDGGuaranteed analysis Typical analysis Guaranteed analysis Typical analysis

Moisture, % - 5.0 - 7.0Protein, minimum % 20.0 22.0 25.0 27.7Crude fat, minimum % 5.0 5.5 5.0 6.6Crude fiber, maximum % 17.0 14.8 16.0 13.7Ash, % - 2.2 - 1.7

For a while some, like the Jack Daniel Distillery,fed the stillage to cattle in wet-feeding operations;but environmental restrictions have generallyeliminated such practices. Also, modern dryerhouse operations have become very profitableand the profit helps lower the cost of makingwhisky.

A modern dryer house will have a wholestillage tank, a centrifuge, press or screen device,thin stillage tank(s), fiber dryer, evaporator anddried grains storage bins. The centrifuge, pressor screening device separates the heavy, fibrousgrains, which are fed to a dryer. The thin stillageis fed into an evaporator and concentrated to asyrup with 40% solids. This syrup is mixed withdried fibrous material in a mixer and fed to thedryer(s), where it is dried to 8-10% moisture(Table 5).

Distillers dried grain is high in protein (24-30%), and is sold primarily in the cattle feedmarket. One distiller dries the fiber and solublesportions separately, selling the fiber portion basedon its fiber content and the solubles as distillerssolubles in the high protein (40%) markets. Thedistillers dried grains with 24-30% protein will sellfor $180/ton, making it a very profitable by-product. Distillers solubles will bring a greaterreturn owing to its higher protein content. Inthe modern distillery, the value of the by-productrecovered will be credited against grain costs andis a major factor in maintaining low proof gallonproduction costs.

Cooperage and maturation

Cooperage and maturation are the processingfactors that distinguish bourbon and Americanwhisky from the other whiskies of the world.Only bourbon whisky regulations require that itbe matured in a new charred, white oak barrel.Other whiskies of the world may require the useof small wooden barrels, but no other whiskybut bourbon goes through the care and expenseof requiring small white oak barrels to be freshlycharred.

The making of the bourbon whisky barrel is avery traditional, but exact science and craft.Staves and heading are quarter-sawed frommature, white oak timber. Actually, somephysical variance exists within a single tree, butno more than between trees. After beingquarter-sawed with the medullary rays not lessthan 45 degrees to the stave surface, the stavesand heading are air-dried in a stave yard. Themore traditional distilleries require wood to beair-dried at least one year. The modern distilleryusually has no air-drying specifications and allowsits barrels to be produced from wood that hasbeen air-dried for six months or less. All of thewood is kiln-dried at the cooperage, with stavesand heading dried to 12 and 10% moisture,respectively. The kiln-drying is essential to preparethe wood for the planing, milling, edging andjoining operations that cannot be done on wetwood. More important, however, is that properdrying (air-drying a year followed by kiln-drying),

Production of American whiskies: bourbon, corn, rye and Tennessee 223

makes the wood chemistry satisfactory forflavoring the whisky during maturation.

As the whisky goes through maturation (3-4years for the modern distillers and 4-8 years forthe traditional distillers), two distinct types ofreactions occur: reactions between the distillatecomponents (regardless of the barrel); andreactions that occur when the distillate extractschemical compounds from the wood. A majorfactor differing among the distillers is thewarehouse environment. Most modern distillersheat their warehouses in winter. One particulardistiller even controls the heat cycles to ensureconstant aging. The traditional distillery seldomhas heated warehouses and depends strictly onMother Nature to determine the number andrange of its heating and cooling cycles.

Whether the heat cycle is natural or forced,the greatest rate of change or formation ofcongeners occurs in the first 12-16 months. Onlyester formation occurs at a fairly constant rate.Proof increases at a fairly constant rate of 4-5%each year of aging. Other specific changesoccuring when the distillate reacts with thecharred wood are: a) aldehyde formation,specifically acetaldehyde, which comes from thealcohol via oxidation, b) acetic acid formationwith greatest activity in the first year of maturation,and c) ester formation (ethyl acetate) from thealcohol via oxidation. The components comingfrom the wood are tannins, sugars, glycerol andfructose. The hemicellulose in the wood appearsto be the source of the sugars found in agedAmerican whiskies.

The depth of charring and �toast level� in thebarrel determines the color of the whisky. Colorformation is almost instantaneous when thedistillate is put into the charred barrel, with 25-30% of the color formed in the first six months.Some color development occurs each year ofmaturation until the whisky is dumped from thebarrel. The final product is then filtered, its proofreduced with demineralized water and bottled.Compared to the sweet rums, �breathless vodka�,fruity gins, light Canadians and Scotches, theAmerican whiskies have flavor and bravado witha balance that is pleasant to the taste. Americanwhisky produced and matured as described hasa big, pungent aroma that leaves no doubt that itis bourbon or Tennessee whisky.

Though the modern and traditional distillershave different levels of technology, they bothuse the same basic processes for makingbourbon or other American whiskies. Individualplant nuances produce different flavors, but theyall have an American whisky bouquet and taste.

References

Carson, G. 1963. The social history of bourbon.Dodd, Mead & Company, New York.

Connelly, W.E., and E.M. Coulter. 1922. Historyof Kentucky, Vol. II. The American HistorySociety, Chicago and New York.

Lyons, T.P. 1981. Gasohol, A Step to EnergyIndependence. Alltech Technical Publica-tions, Nicholasville, Kentucky.

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