The Distillation Process
Upon arrival at the distillery the grain is carefully inspected and cleaned of all dust. It is then ground in the gristmill to a meal. The meal is first cooked to release starch from its tough cellular coating, then malt is added to convert the starches. This mixture, now called wort, is set aside to cool. Pure cultured yeast is propagated in a yeast tub in the distillery. The cooled wort is yeasted with the propagated yeast and goes to the fermenting vats to become beer. The beer goes onto a patent, or double column, still. The result is whisky, which is distilled out at below 160 proof. It is then reduced in proof to 105 to 110 by adding demineralized water. All new Whisky (except corn and light Whisky) is placed in new charred white oak barrels to mature in the distiller’s warehouse. American Whisky is barreled at 105 to 110 proof and as they mature their alcoholic strength increases because of the warm, dry conditions under which they are stored.
There are two yeasting processes used in America, the sweet mash or yeast-mash process and the sour mash or the yeasting-back process. The sour mash process is used primarily in making Bourbon Whisky.
- A Sweet Mash Whisky is produced by adding all or almost all freshly developed yeast to the mash, that is, no stillage (liquid recovered after the alcohols have been distilled off) from a previous distillation is mixed with the fresh mash to adjust the acidity. It is allowed to ferment from 36 to 50 hours, and the fermenter is refilled almost immediately when empty.
- Sour Mash Whisky means that a least one quarter of the fermenting mash must be stillage, or spent beer, from a previous distillation, along with fresh mash. The mash is allowed to ferment from 72 to 96 hours. Fermentation generally takes place in open fermenting vats at low temperatures. When emptied, the fermenters are sterilized, aerated and allowed to “sweeten” for 24 hours before being used again.
There are three main categories of American whiskies:
- Straight – A straight Whisky is one distilled off at a proof not exceeding 160, aged in new, charred oak barrels and reduced by the time of bottling to no lower than 80 proof, from a minimum of 51 percent of a single grain. Nothing may be added other than water.
- Blends – To be a blended Whisky, at least 20 percent of the blend must be straight Whisky. The balance may be grain neutral spirits, grain spirits, and /or light Whiskies. Also 2.5% by volume can be certain blending materials such as sherry wine, prune or peach juice.
- Light – Light Whiskey is whisky that had been distilled at more than 160 proof, less than 190 proof and stored in seasoned (used) charred oak barrels. The primary purpose for this category was to permit production of light distillates that could be aged in used oak casks to develop the lower flavor intensities found in this type of Whisky. The biggest use for light Whiskies is in blends, as a replacement for grain neutral spirits.
American Whiskey is commonly divided into six types: Bourbon, Tennessee, Rye, Wheat, Corn and Blended Whiskey. The types are mainly motivated by differences in the type and amount of grains used during the mashing, but there are also differences in storage time.
- Bourbon Whiskey – Because of the fact that almost all Bourbon is made in Kentucky many people believe this is a requirement, but in fact Bourbon may be produced in any state. The only prerequisites are that it must be made in the U.S., contain at least 51% corn and stored for at least two years in new, charred oak barrels. Lastly, the raw spirit may not be distilled to more than 80% alcohol by volume.
- Tennessee – Tennessee Whiskey is closely related to Bourbon but there are a few differences; Tennessee Whiskey must be produced in the state of Tennessee and is always filtered through sugar-maple charcoal. The filtering process usually takes 10 days to complete. This Whiskey can be 51% of any grain, although corn is usually used. Tennessee Whiskey was recognized as a separate style by U.S. government officials in 1941.
- Rye Whiskey – Only a small amount of Rye Whiskey is bottled as Straight Rye Whisky –most of it is used in blending to add character to other Whiskies. To be called a Rye Whiskey, the spirit must be made from at least 51% rye, distilled at less than 80% and stored in new, charred oak barrels for at least two years. Rye Whiskey is slightly more powerful and bitter than Bourbon. Most current Rye whiskies are made in Indiana and Kentucky.
- Blended American Whiskey – The blended American Whiskey should not be confused with the blended Scottish Whisky. Blended American Whiskey only contains 20% of Rye and Bourbon Whiskey; the remaining 80% is made up of a neutral mass-produced industrial spirit. As a result, American Blended Whiskey is very cheap. It is also much lighter than for example Tennessee and Bourbon Whiskies.
- Corn – This type of American Whiskey was developed due to the abundant supply of corn, and is a predecessor to Bourbon. As the name suggests corn is the main ingredient; the mash must consist of at least 80% corn. Another difference between Corn Whiskey and Bourbon is that Corn Whiskey does not have to be aged in wood. If Corn Whiskey is to be aged, any maturation must be done in either un-charred barrels or used Bourbon barrels.
- Canadian Whisky – Many people believe that Canadian Whiskey is a Rye Whiskey, which it is not. Corn, wheat, rye, and barley malt are the grains generally used, and none can be more than 50%. The distillers have developed a Whiskey with a delicate flavor and light body. They obtain these characteristics with mash formulas designed to produce lightness and delicacy and by distilling out at varying strengths, ranging from 140 to 180 proof. Practically all Canadian Whiskey is six years old or older when marketed. If it is less then four years old its age must be listed on the bottle. Today there are few if any similarities left between American Whiskey and its cousins the Scottish and Irish Whiskies. For example, no smoke is used to dry the corn, rye or wheat, which are used in American Whiskey. Because of this, American Whiskey often has a fuller, stronger and sweeter taste than its European counterparts.
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Content provided by Keith Cox, Martin Wine Cellar