Popular Demand Wins; Bourbon Whiskey it Is!

Crossposted at Dailykos.com

Bourbon whiskey is the quinessential American product. The Canadians make something like it, but usually use some neutral spirits to “soften” it a bit.

First, a couple of definitions. By federal law, bourbon must be made from at least 51% maize (corn) and has to be aged for at least two years in new, charred, oaken barrels. It also has to come out of the still with no more than 80% alcohol content. There is a technical reason for that.

Once you start distilling much over 80%, you are really making neutral spirits, mostly pure alcohol essentially devoid of flavoring agents (called “congeners”) that give a particular product its character. Also, the first fraction that is very nearly 95% alcohol (called the “high shots”) contains several low molecular weight materials that are irritating if not outright toxic, as if ethanol is not.

Well, let us get down to brass tacks. Bourbon is essentially made from corn, and carries much of its character with it. But the secret is that much of it is made with barley malt, as well. There is a technical reason for that.

Barley seems to have one of the most active enzyme systems that produces disaccharides and monosaccharides from starch. Those are something that yeast can use for food. And as soon as the mash or wort is cool enough, the pitch in the yeast (actually in beer, wine, or whiskey making, adding the yeast is called “pitching”), then they control the temperature for about a week, give or take, depending on the brand. Some processes take old, expired mash from the last batch and add it to the new batch. This is the “sour mash” process, and purportedly keeps the same strain of bugs (yeast) going from generation to generation. Other processes use new yeast cultures every time. There does not seen to be a whole lot of difference, because the most significant items that flavor bourbon are the while oak casks, and the way that they are handled, stored, and treated. This is much more art than science. I know that there are those who will disagree with me, but those are the facts.

Anyway, it is not essential to use barley malt, but some kind of malted grain has to be added to convert the starches in the unmalted grain to sugar, which the yeast can process. I can speak with a little authority, since I am from the hill country in Arkansas: real old timers would malt their corn, then dry it, and take it to the miller for grinding. The miller asked no questions, and took her or his fee (a fraction of the grain being milled) the next time that the customer brought unmalted corn to be ground. It is possible to make perfectly good whiskey with only corn, but since corn has less enzymatic activity than barley, it takes more malted corn to do the job, and that takes room, time, care, water, and kilning at the right stage in excess than that required for barley.

Anyway, here is the basic process, and there are as many subtle variations as there are brands. The grain blend chosen (at least 51% corn, by law) is ground, it is cooked (mashed) at a temperature below boiling (boiling inactivates the enzyme that converts starch to sugar). After the conversion process is complete, the mash is boiled to sterilize it. Sometimes the solids are removed before boiling, sometimes after. Sometimes they are not removed. Then the liquid (called wort, or by the old ’shiners, beer) is pitched with yeast and held at a temperature favorable for the particular strain of yeast being used.

After the sugars have been converted to alcohol for the most part, the solids are separated (if they have not already been) or not, and the material transferred to the still. The best Bourbon is distilled in pot stills, which, whilst they do separate water from alcohol, allow other components to distill with the alcohol. In contrast, neutral spirits are produced in a “patent” still, which pretty much is designed to give pure fractions, devoid of flavoring material, hence the term “neutral”.

For you chemistry geeks out there, like me, the difference is that a pot still has only a couple of theoretical plates, where a patent still can have up in the hundreds, depending on the design. The more plates, the sharper the separation of components. For example, crude oil is distilled in a patent still, which allows cutting fractions from gases, gasoline, Diesel fuel, fuel oil, and so forth.

A pot still is much like Granny’s one on The Beverly Hillbillies, except that one was not accurate in one respect: the condenser coil is always water cooled, and hers was air cooled. Even the old ’shiners used water to cool the condenser, otherwise most of the product would be lost.

By law, the “high shots”, a product over 160 proof (80% by volume) alcohol can not be used. This fraction contains a lot of low molecular weight components, and they do not contribute to the character of Bourbon. By the way, it is impossible to distill a water and alcohol mixture in such a way that 100% (200 proof) alcohol results. This is because a mixture of 95% alcohol and 5% water (by volume) forms what is called an “azeotropic mixture”, and its boiling point is lower than either water or alcohol, so 95% is is good as you can get. That is why pure grain alcohol is 190 proof, not 200.

There are ways to remove the 5% of water in alcohol, but do not have much, if anything, to do with beverages. If you are drinking 190 proof alcohol, there is a problem fundamentally.

As the distillate comes to 160 proof, it is collected, and continues to be collected until little alcohol comes over and the temperature rises. The goal is to get a product between 80 and 100 proof (40% to 50% alcohol by volume), but it is often a bit higher. Water is blended to make it correct.

Then the distilled product is sent to the barrel. Some processes filter the product through charcoal first (Jack Daniels, not technically a Bourbon, but functionally one, does this). This is the secret of Bourbon. By law, Bourbon has to be aged in new, charred, white oaken barrels for at least two years, and experts agree that more is better. The chemistry and physics are extremely complex.

By charring the barrels, many complex chemical substances are produced (they are usually charred with a hot gas flame). These include phenolic compounds, other aromatic materials, and just a wee bit of methanol (wood alcohol, a violent poison, most of which is driven off by the heat). But it also produces an active carbon layer that absorbs many of the toxic materials from the fermentation and distillation process.

The charred barrels (and uncharred ones, too) also release tannins into the alcohol, giving it color. Bourbon just going into the barrel is water white. The barrel gives it the nice color associated with it. Then the aging process is continued for a couple of years to decades, depending on the brand, quality, and price.

After aging, the barrels are sampled for color, scent, taste, and alcohol content. If any are off, they get sent to a buyer who will use it for cheap American whiskey, which is not subject to as strict a set of regulations as Bourbon. The ones that make it are drained and mixed with other good barrels in the mix house. Then a team of tasters and chemists examine the product and determine how much water needs to be added to get the proper proof, if the product is consistent with previous batches, and other quality factors.

Some distilleries actually blend older batches with newer ones to keep the slow changes in taste and color more stable. It is not possible to distill any whiskey today that is identical with one distilled 100 years ago, but you can get close. This is because that there is a lot of biology involved in getting the starch to sugar, different strains of corn being grown, and just the luck of the batch.

Now comes bottling. Most distilleries have automated bottling lines that squirt a measured volume of Bourbon into appropriately sized bottles, a labeling machine, and a capper. Unlike beer or wine, it is OK to introduce air into whiskey because it has a high enough alcohol content to kill or suppress any germs that would degrade it, so it is its own preservative. High speed lines are the norm in large operations, and does not really degrade the product.

Just before bottling, the material is gauged by the government to determine the tax. Since there are losses in alcohol content in aging, the final product is taxed. The angels get theirs free of tax.

Now it is boxed, packed, and trucked to your local store.

I hope that this has been interesting and illustrative.

Warmest regards,

Doc

Tags: Bourbon, Bourbon Whiskey, Learning, Teaching, Whiskey, Whisky