Pique the Geek 20110109: Bourbon or Tennessee Whiskey?

(9 pm. – promoted by DDadmin)

This topic was suggested by our good friend and regular supporter of this series from The Big Orange, Ottery Scribe.  It is really a fascinating subject, and rich with lore and tradition from the old countries.  As a disclaimer, I must say that I do not really enjoy either of them except for an occasional 12 year old Old Charter, diluted with some cold water.

I actually used half a pint of bourbon just before Christmas, to plump the raisins that I use for my trademark Lizzies fruit cookie.  Look back to just before Christmas for links to the recipe for them.

First, we need to define what whiskey (or whisky) is.  Whiskey is roughly defined as a spirituous beverage distilled from a mash of grain, some of it malted, and aged in some fashion, usually in oak, for a given length of time.  Whisky is pretty specific for those liquors made in Scotland, and they are unique in a couple of ways.

I shall use the more general term whiskey unless specifically referring to Scots’ whisky.  Whiskey is distinguished from rum in that rum is based on molasses, usually byproducts of the sugar industry.  Brandy is based on the distillation of grape wine (unless there is a qualifier, like peach brandy which is supposed to be distilled from a wine made from peaches (although now days it is often proper brandy flavored with peach essence).  Perry is a special brandy distilled from pears.  The thing that distinguishes most of this group is that most (but not all) are aged, usually in oak, for some period of time.

Folks have been distilling alcohol from just about anything that has sugar and/or starch in it.  For example, tequila is distilled from the fermented agave plant, and vodka is made from just about anything.  Gin is traditionally made from grain, and in Asia a number of products are distilled from rice.  But this is supposed to be about whiskey.

To understand how whiskey distillation became American, it is necessary to look at the traditions from Britain, Ireland and Scotland in particular, because it was largely immigrants from those two countries that pioneered the whiskey art in America.  It is also important to note that the spirit that was most popular in colonial America, and for some time afterward, was rum, for a number of reasons, at least one of them being the support of the slave trade in the notorious Golden Triangle of trade betwixt Great Britain, the West Indies, and America.  For some reason, Africa is usually left out, but picking up slaves was an important component of the trade.  But I digress.

In Scotland and Ireland, most whiskey was distilled from barley and barley malt.  Note that even yet in Europe, a “corn” refers to a grain of barley, and what we call in North America corn is called maize in Europe.  This causes a lot of confusion to those who are not familiar with that point.  I shall use the term “corn” for maize, unless qualified such as a “barleycorn”.  By the way, for you trivia buffs, the inch was originally defined as three barleycorns laid end to end.

The word whiskey is of Celtic origin, coming from uisge beatha, later contracted to usquebaugh.  Both of these words loosely translate to “water of life” (what a misnomer!), and similar words are found in other languages, such as the French eau de vie.  The Latin aqua vitae means the same thing.

Traditionally, both Scots’ and Irish whisky was made from a mash of barley and malted barley with no other ingredients except water and yeast.  Malt is important because it converts the starches in unmalted grain to sugar, and yeast can ferment only sugar to alcohol.  A malted grain is simply any grain that has been induced to sprout, then being dehydrated to arrest its development.  As a grain sprouts, its nascent metabolism causes production of enzymes, called diastases, that have the ability to split the large polymers of starch into simpler sugars.  This is important for the grain to develop and grow properly, since the starch is its its food reserve.  Barley is unique in that it develops more disatatic activity than most any other grain.

Barley is also unique in that it grows well in colder climates than many other grains, making it ideal to grow in Ireland and Scotland (and also Germany, where it is the basis of beer).  Wheat does not do well in the British Isles, but barley grows well.  Now, since the malting process is labor and resource intensive, only the minimum amount of grain is malted, and that malted grain mixed and gently cooked with unmalted grain to convert its starch to sugar, too.  By the way, if you look on almost any bag of all purpose flour in your cupboard you well see that one of the minor ingredients is malted barley flour (also called malt flour).  This, when wetted, converts some of the starch in the wheat flour to sugar to feed the yeast.

Unless you want the malt to rot after it is sprouted (traditional malting houses used a layer of grain around a foot thick), you have to dry it out when it is ready.  In Scotland, traditionally fires from peat (the first step after death for a celluotic plant on the way to coal) were used, the hot smoke being passed through the malted barley with raking from time to time, to dehydrate it.  Once it is dry enough, it will keep for a long time if not allowed to get wet.  In Ireland, fires were used to heat fresh air and that air was used to dry the malt.  The difference is that the smokey scent from the peat is imbued into Scots’ malt, and that carries over into the final product.  In the Irish product, no smoke flavor is present.

We are almost finished with the history, but two points are critical yet.  In the traditional distillation processes, pot stills were used to distill the mash into whisky.  These are not very efficient, and allow lots of impurities (some of them quite a bit more toxic than ethanol) to flavor the distilled product.  Depending on the particular facility, sometimes the first distillate would be distilled again, and even a third time (not often for whisky).  But the spirit was still harsh in flavor and needed further treatment.

They looked at what the French and Italians were doing to age their wine, and decided to use oak barrels to refine the flavor and quality of their spirits.  New oak barrels were too expensive, so they started buying used wine barrels or whiskey barrels on the cheap to use.  However, the product from them tasted too much like wine, so they had to fix them.  Hence the process of charring the oaken barrel.  Originally designed to drive out the wine flavor from them, it was soon learnt that charred barrels, used or new, gave a better flavored product than virgin ones did.  The chemistry involved is extremely complex, and would be better to defer the complete treatment of this to the comment section.

So this was the state of the art as the first settlers from Scotland and Ireland came to the Colonies or the early United States.  They would soon find out that almost NOTHING was the same here insofar as raw materials were concerned.

In the first place, barley was not a very productive crop here (until we found that the northern plains decades later), but corn was.  Second, there were no used wine barrels to be had here.  Third, there was precious little peat, and finally, there was somewhat of a hesitance to import spirits from Great Britain.  Remember the bad feeling about tea.

So, our pioneers started to use corn to make whiskey, and even changed the spelling a little (although that might be a function illiteracy).  But corn malt is not nearly as diastatic as barley malt, so some barley continued to be planted here and there.  They also found that the flavor of a corn based whiskey was completely different than that from a predominately barley based one was, and without the smoky, peaty flavor, was sort of hard to drink.  That also had so do with using pot stills that, as I said earlier, and not very efficient.

I do not know, nor does anyone, when the idea of using NEW charred oaken barrels was conceived, but it caught on fast once tried.  The new corn whiskey, after aging in charred oak, developed a flavor that was (depending on the process that distilled the liquor) mellow and had a very complex flavor profile.  The charcoal itself inside the barrel absorbed significant amounts of the more toxic components, and the chemical reactions of charring also produced many compounds related to vanilla (which you can actually smell in a glass of good bourbon) that complimented the natural flavor of the corn starting material.  By the way, the dark color of naturally aged whiskies comes from, in the most part, some tannins naturally in the oak and caramels produced by the heat treatment.

Now, most of the whiskey produced at the time was not nearly as well treated.  Most of it was not aged at all, just jugged after distillation and sold.  Farmers found that taking what I will term “raw” whiskey to town much less expensive than transporting the corn itself, and distilled crude material just for that purpose.  There actually was an armed rebellion, The Whiskey Insurrection, when the Federal government tried to apply an excise tax to the whiskey produced for that.  Remember, Article I, Section 8 of the Constitution explicitly says that

The Congress shall have Power To collect Taxes, Duties, Imposts, and Excises…

and that is what they did, forever imposing an excise tax on domestically produced alcohol (sin taxes are nothing new).  The insurrection was put down, and things settled.

But the pioneers, especially in what is now the Bluegrass region of Kentucky, started to produce a superior product, unlike anything else anywhere.  Using mostly corn, with either malted corn or barley malt to supply the diastase, they began to make a truly superior product, as long as it was prepared properly.  Most settled on barley malt and that pretty much became what we now know as Bourbon, but some used just corn and corn malt, and that is what is legally defined as Corn Whiskey now.  Since the center of this new product was Bourbon County, Kentucky, the new product became to be known as Bourbon Whiskey.  There are tales that the first Bourbons were distilled from grape seeds left over from winemaking in France during the Bourbon dynasty and that is whence the name.  Those are bunk.  Whilst I am sure that a whiskey could be distilled from a grapeseed mash, I can promise you that it would be nothing like Bourbon Whiskey as we know it.

I shall get into the unique properties of the components about Bourbon in a little while, and the legal definition for it, but now intend to go a bit further south to Tennessee.

The settlers there produced a product that was essentially identical with Bourbon, except that they added one, fairly expensive step.  Before going into the oaken barrel for aging, the raw distillate is passed through a thick layer of maple charcoal.  As a chemist, I know what this does.  It removes almost all of the relatively more toxic materials from the distillate by adsorption, and thus provides a more pure alcohol product to the oaken barrel. Otherwise, the processes are just about the same.

Here are the processes, and the legal requirements as we go.  It gets a little Geeky, but what can I say?

-To be called Bourbon, the mash has to be composed of at least 51% corn, other than the water.  Other ingredients are not regulated.  Usually it is more like 75% to 80%, since corn is one of the cheapest starch sources, although that is changing because of the foolish use of perfectly good corn for fuel.  Barley malt is usually the bulk of the rest.  Rye and wheat are also often used to make up the rest of the starch.

-The maximum alcohol content in the distillate can be no more that 80%.  This is critical, because at higher alcohol concentrations, flavoring ingredients are lost.  This might be the most important regulation, other than the ingredients and aging.  Since the really toxic components are very low boilers, the first bit (the high shots),  are discarded.  That is where the acetone and methanol lurk, neither of which do you want to drink.

-In going to the oaken (NEW), charred barrel, the maximum alcohol content is 62.5%.  That means that you keep distilling the mash until you are much lower than 80%, and some of the flavoring agents are in the low shots as well.

-It has to be in contact with oak for at least one second.  I just made that up. However, it is a legal requirement that it contact new, charred oak.  To be called “straight”, it has to sit there for at least two years.  Most connoisseurs agree that the longer in the oak, the better the product is.  That may be mostly right, but not always.

-No coloring nor flavoring agents can be added.  Only the distillate and whatever it picks up from the charred oaken barrel are permissible.

-When bottled, it has to be at least 40% alcohol, and more is permissible.  The alcohol content has to be stated on the label.

-To be labeled as “Bourbon”, without qualification, the material is required to be produced in the United States.  There is no state restriction on that.  It is one of those international trade agreements.

The question has arisen as to why Bourbon is mostly made in Kentucky, in particular the Bluegrass region.  It has to do with the water.  To make good Bourbon, very “hard” water is needed, but there can not be any iron in it.  The Bluegrass region has such water and that is why so much Bourbon is made here.  In other regions with high calcium, low iron water it is possible to make a good product.  The water requirements for Tennessee whiskey are similar.

Now, Tennessee Whiskey, as I said before, is essentially Bourbon with a charcoal treatment before casking.  There are some legal restrictions on using that name, and as far as I know only whiskey produced in Tennessee can legally be called that.  However, the requirements for Bourbon are Federal, so I expect that Tennessee whiskey could be produced with a lot more flexibility insofar as ingredients and aging processes than the legal requirements for Bourbon demand.  However, I do not find a whole lot of sensory difference.  I used to drink Dickel, many years ago, but sense I lost my taste for that kind of liquor do not much use it.

No discussion about aging whiskey would be complete without mentioning the chemistry and physics involved in it.  I know, I said to reserve it to the comments, but is is the third leg of whiskey making.  The aging process is intimately connected with the chemistry of the wood components and the physics of the very structure of the wood, along with the properties of the components of the whiskey itself.  The same general principles also apply to rum and brandy, if casked in oak.

By putting a distillate into an oaken barrel (we will assume a new, charred one), several things happen.  First, the char of the interior begins to adsorb the more polar molecules, and that mellows the liquor.

More importantly, when the barrel is charred, the lignans react by Maillard reactions to smaller molecules like vanillin (the prototype scent of vanilla), ethyl vanillin (a more potent one), and several other derivatives.  This gives it its unique taste, along with other extractions that we might not ever understand.  I believe that I mentioned earlier that color is gained by extraction of some of the tannins from the wood.

As the whiskey ages, another interesting thing happens.  Since wood is porous, the liquid soaks into the barrel.  Now, since alcohol is more volatile than water, it preferentially evaporates and so is lost.  Thus, the whiskey becomes “weaker” with time.  This is one reason why whiskey that is aged for a very long time is expensive (the cost of storing the barrel is another component).  In Scotland, the amount of alcohol that is lost due to evaporation is called the angels’ share.  This is why liquor is taxed at the time of bottling rather than at the time of casking.

Most Bourbon and Tennessee whiskey is blended at the time of bottling.  Tasters at the caskhouse sample each barrel that is aged long enough and select which ones to blend to provide a consistent product.  Rarely, single barrels will be selected to be bottled without blending if the contents are particularly good.  Whiskey that does not meet the flavor standards of the particular brand is not discarded, but is rather either blended in house or sold to brokers to make cheap brands.  There is too much investment in materials and aging time to waste it, even if it is not very good.

After the barrels are drained and the whiskeys blended, a check is done for alcohol content, and water is added to dilute it to whatever is indicated on the label.  Bourbon and Tennessee whiskey is typically diluted to 40% alcohol by volume, but other concentrations are also used, often 43% and 45%.  A few brands are stronger.  By law, Bourbon has to be at least 40% alcohol by volume to be bottled.  As it it bottled the tax is calculated and paid.  Then the product is ready to be sent to the wholesaler.

The used barrels are not legally allowed to be reused for Bourbon.  A few of them are sold to the public for use for planters and such, and there is even a specialty furniture manufacturer that uses them for patio furniture.  White oak is not very good for planters or outside furniture, however, since it is not very decay resistant.  By far the biggest market for used barrels is Scotland, where they are used for Scots’ whiskey.  Remember, they started out using old wine casks, and have adopted old Bourbon barrels quite well.

Finally, I think that I should talk about the term sour mash.  This is not understood by most folks, but is really simple.  After the mash is fermented, the liquids are drawn off, the grain extracted a couple of times with hot water, and the liquid portion distilled.  The remaining solids are typically dried and marketed as animal food.  In the sour mash process, some portion of the spent solids are added to the next batch of new mash.  The theory is that by doing that continuity in the flavor of the final product is improved.  I am a bit dubious as to whether that is very important these days, with pure yeast cultures, but in the old days it was necessary to use a bit of the old mash to introduce good yeast into the next batch, just like sourdough bread.

Well, you have done it again.  You have wasted many more einsteins of perfectly good photons reading this mash of a piece.  And even though new Republican members of the House decide to take the oath of office before they start voting when they read me say it, I always learn much more than I could possibly hope to teach by writing this series.  Therefore, please keep those comments, questions, corrections, and other thoughts coming.  Remember, no science or technology issue is off topic in the comments.

Warmest regards,


Featured at TheStarsHollowGazette.com.  Crossposted at Dailykos.com


Skip to comment form

  1. traditional beverages?

    Warmest regards,


  2. Love a good Cabernet.

    But all very interesting Doc.  

    My Dad had a PhD in biochemistry and taught medical and grad school for forty years.  I learned a lot of chemistry by osmosis.  My brother is a PhD in biophysics (research at a University only) but mostly does biochemistry.  Unfortunately I didn’t get the genes.  At least not the good ones.

    Nevertheless, all your chemistry posts interest me.

    I have a special interest in charoal.  I am sure I have posted about terra preta before and how the charcoal in terra preta greatly improves the soil by doing the same as it does in whiskey production — absorption of minerals — and then holds them to make for a very fertile soil.

    It is interesting in whiskey making that they char the inside of the barrels, and I wonder how they do that, in what I presume would be a uniform char.

    The miracles of charcoal.

    I may have posted this video on how to make charcoal for biochar before.  If so forgive me for the repost.  But I find it interesting.


  3. front page, DDadmin!  I appreciate it.

    Warmest regards,


  4. I think that’s Kentucky.  Also Buffalo Trace, no idea where that’s from.  Isn’t Jack Daniels Tennessee?  Oh, and thanks for the entertaining and informative essay.  

Comments have been disabled.