Aficionado or connoisseur, devotee or fan, those who understand the difference between bourbon and whiskey are already familiar with which is better for distilling.

Distilling whiskey involves the use of starchy grains, which are ground into a mixture, hence the term “mash.” The mash is then fermented before it is distilled, blended, and then finally aged. This is the point at which we can distinguish what separates bourbon from whiskey, despite the fact that most people assume they are one and the same.

While bourbon falls into the whiskey classification, not all whiskeys are bourbons. To be classified as bourbon, the grain mash used in distilling the whiskey must contain at least 51 percent corn and be aged a minimum of two years inside a new, oak barrel. Bourbon distillers typically have all the necessary materials to make new casks.

Another misconception is in thinking the term sour mash refers to the bourbon’s flavor, although it does have to do with producing a consistent taste.

Sour mash is a process. Sour mash distilling is akin to the process of making sourdough bread using a starter to achieve a consistent taste from one loaf to the next. By adding some of the spent mash, which is the previously fermented mash that contains live yeast, the home distiller is better able to control the yeast growth, thus producing a consistent spirit from one bottle to the next.

Both bourbon and sour mash whiskeys are descended from the moonshine that was originally produced in Kentucky and Tennessee. While connoisseurs may continue to debate over which is the superior brew, all would concur that they both comprise the distinctive American distiller’s craft. There are even societies devoted to the study of these uniquely American spirits.

Bourbon Whiskey is Made in the United States

Named for the French-Bourbon dynasty at the time, bourbon whiskey first began in territorial Kentucky. Blue Ridge Mountain distillers in both Kentucky and Tennessee managed to hide from revenue agents during the Whiskey Rebellion of 1791, which had everything to do with allowing the moonshiners to thrive in an unregulated industry. The successful production of these mountain distilleries eventually evolved into the refined bourbon and sour mash that famously hail from these parts today.

It was not until 1964 that the U.S. Congress ruled that bourbon whiskey is a “distinctive product of the United States,” and Federal regulation defines bourbon whiskey to include only bourbon that is produced in the U.S. Bourbon-makers do exist in other counties, however, only the bourbon produced in Kentucky is permitted the use of the name of the state on its labels.

The labels hold useful information to help you identify the whiskey. For example, by law, to be labeled Sour Mash Kentucky Straight Bourbon Whiskey, this bourbon has not been blended with other whiskeys, has been produced using some of the mash from a previous batch, which is the “sour mash,” and the entire product was made in the state of Kentucky.

While Tennessee whiskeys are produced using corn mash distilling, makers may only specify “sour mash” on the label if that process is used. These spirits may use the same bourbon recipe, but they are filtered through maple charcoal to achieve a different overtone. The strongest influences on the taste of bourbon are the grain, the yeast strains and the new, oak barrels. As well, even the type of wood used will contribute to the taste.

Both Kentucky and Tennessee are located where large limestone layers filter the water to a superb clarity for whiskey production and is considered by Kentucky bourbon distillers to be a signature element in their sour mash process. The predominant grain used to make all bourbon is corn, at least 51 percent. It is preferred for the sweeter, robust vanilla and maple syrup flavors that come from the sugars. Unlike the single malts made entirely from barley that come from Scotland and Ireland, rye, barley and wheat tend to be added to make up the balance of grain contained in the mash.

It All Starts with Corn Mash Distilling

Small Yeast Bubbles of Yellow Bourbon Mash with selective focus

It is generally thought distilling began in Kentucky in the late 1700s introduced by the Scots, Scots-Irish from the province of Ulster and others including the English, French, Germans, Irish and Welshmen. The possibility of identifying a single inventor of either whiskey or bourbon is unlikely.

Charring barrels for enhanced flavor when aging whiskey is a centuries-old practice in Europe. It was inevitable that this practice would migrate with the settlers.

Numerous counties were founded in the vast regions west of the Allegheny Mountains proceeding the American Revolution. Despite the region’s burgeoning growth, most people continued to refer to this area as Old Bourbon. As it happened, the main port in Old Bourbon where the whiskey was shipped was located on the Ohio River in Kentucky.

To indicate their port of origin, “Old Bourbon” was stenciled on the barrels. Like it or not, this strongly associated any corn-based bourbon whiskey with the name Old Bourbon. Most often, this was the first taste of corn whiskey most people ever had. In Tennessee, they prefer to call their bourbon “Tennessee whiskey” instead. The production process for both Kentucky Bourbon and Tennessee Whiskey are the same except that Tennessee whiskey is charcoal-filtered before going into the barrels.

Your Choice of Grains Influence the Flavor

Whether starting as whiskey or intended to be made into bourbon, it all starts with a mash bill that requires the minimum 51 percent corn with any cereal grain making up the remainder. Wheated bourbon is the result of using wheat in the mash bill instead of rye making it milder and smoother on the tongue. A higher rye content produces a dryer, spicy whiskey. The corn sugars produce a rich and syrupy quality and lends to a leathery finish as the spirit is aged. Craft whiskey distillers experiment with many different grains as accents to the corn.

Corn whiskey may either be unaged or aged in previously used barrels. You can really taste the corn influence in these whiskeys as there are little to no barrel flavors influencing the batch. If mash from a previous distillation is added to the corn mash to ensure consistency, then you have a sour mash. Most bourbons today are run off a column still that is then redistilled in a thumper. The clear spirit produced from this process is called “white dog,” which is placed in the charred new oak casks for the aging.

Sour Mash Distilling is Essentially Yeast Management

The yeast strains possessed by Kentucky and Tennessee distilleries have survived since prohibition with patents filed for their isolated yeasts. The primary purpose of the sour mash is the control of yeast reproduction with the pH balance being key to this process. Even the object used in this process are autoclaved to ensure no foreign element contaminate the desired yeast strain. The consistency of the batch depends upon this careful handling.

The sour mash process is much-praised for its ability to create an acidic environment for the yeasts. When prepared with fresh spring water as it is in Kentucky and Tennessee, its chemically neutral condition is neither acidic nor alkaline. With a pH of about 7, the yeasts cannot work correctly. It is the addition of the sour stillage, or mash, with a lower pH of between 5.0 and 5.4 that leads to the acidification of the entire mash. This brings the pH up to between 5.4 and 5.8, which is ideal for the yeasts to work properly.

Clearly, you can see the advantage to using sour mash when your goal is to achieve consistency in your white dog or if you intend to market your product as straight bourbon. The decision is ultimately yours, but at least now you have some knowledge as to the laws and regulations that come to bear upon how you identify your distillations.