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American single malt whiskey is a burgeoning category that has been gaining significant attention and acclaim in recent years. While single malt whiskey (or whisky as the Scotch spell it) is traditionally associated with Scotland, American distillers have been making their mark by crafting unique and high-quality single malts that reflect the diverse terroirs and innovative spirit of the United States.

Whisky distillation has a long history. The earliest written record of whisky dates back to 1405 in Ireland, as noted in the Irish Annals of Clonmacnoise, where it was mentioned that a clan leader died after consuming an excess of “aqua vitae” during Christmas. In Scotland, the first mention of whisky production from malted barley appears in the 1494 Exchequer Rolls, which records: “Eight bolls of malt to Friar John Cor, by order of the King, wherewith to make ‘aqua vitae’.”

The concept of single malt whiskey has long been dominated by Scottish distilleries. However, American distillers have embraced this style and adapted it to their own traditions and resources. The American single malt whiskey movement began to take shape in the early 2000s, with craft distilleries leading the charge. These pioneers sought to create a distinctly American expression of single malt whiskey, drawing inspiration from both traditional techniques and innovative practices.

The production of American single malt whiskey is a meticulous process that combines traditional techniques with innovative practices. Each step, from sourcing the barley to bottling the final product, contributes to the unique character and quality of the whiskey. This attention to detail and commitment to craftsmanship is what sets American single malt whiskey apart in the world of spirits.

American single malt distillers now follow the official standards set forth by the U.S. Treasury Tax and Trade Bureau (TTB) for American single malt whiskey. The TTB has officially recognized American single malt whiskey as a distinct category, with the new standards set to take effect on January 19, 20252. These standards were proposed in July 2022, and after a public comment period that ended in September 2022, the TTB finalized the guidelines in December 2024.

The American Single Malt Whiskey Commission played a crucial role in this process by submitting the proposed guidelines and advocating for the establishment of a formal definition and standards for American single malt whiskey. The new standards require that American single malt whiskey be made from a fermented mash of 100% malted barley, distilled at a single U.S. distillery to no more than 160 proof, and aged in oak barrels no larger than 700 liters. Additionally, no neutral spirits, flavoring, or blending materials are allowed, except for caramel coloring, which must be disclosed on the label. The designation “straight” can be used for American single malt whiskey aged for a minimum of two years.

This landmark ruling has been celebrated by industry leaders and distillers, who believe it will protect the integrity of American single malt whiskey and drive innovation and creativity within the category

Malted Barley

The foundation of any single malt whiskey is malted barley. American distillers often source their barley locally, which can impart distinct regional flavors to the whiskey. The terroir, or the environmental factors where the barley is grown, plays a significant role in the final taste profile. For instance, barley grown in the Pacific Northwest might have different characteristics compared to barley from the Midwest. This local sourcing not only supports regional agriculture but also adds a unique American twist to the traditional single malt.

Malted barley is produced through a process called malting, which involves three main stages: steeping, germination, and kilning. First, barley grains are soaked in water during the steeping stage to increase their moisture content, initiating the germination process. During germination, the grains are spread out and allowed to sprout, activating enzymes that convert the starches in the barley into fermentable sugars. This stage typically lasts several days. Finally, the germinated barley is dried in a kiln to halt the germination process and develop the desired flavors. The resulting malted barley is then ready to be used in the production of whiskey, providing the essential sugars needed for fermentation.

Once the barley is malted, it is mashed to extract fermentable sugars. This involves mixing the malted barley with hot water to create a mash. The mash is then transferred to fermentation tanks, where yeast is added to convert the sugars into alcohol. The fermentation process can vary significantly among distilleries. Some use traditional open-top fermenters, which allow for natural yeast and bacteria to influence the fermentation, adding complexity to the flavor. Others use closed fermentation tanks to maintain more control over the process. The duration of fermentation can also vary, typically lasting from a few days to over a week, depending on the desired flavor profile.

Distillation Process

 American single malt whiskey is commonly distilled in copper pot stills. Copper is favored by many distillers because it reacts with sulfur compounds in the mash, removing unwanted flavors and resulting in a cleaner, smoother spirit. The use of copper also helps to concentrate the flavors and aromas, contributing to the overall quality of the whiskey. However, distillers also use column stills, hybrid stills, and chamber stills to create unique and diverse expressions of this growing category. This variety in distillation methods contributes to the rich and varied landscape of American single malt whiskey.

As previously stated, American single malt whiskey must be distilled to no more than 160 proof (80% ABV). This limit ensures that the spirit retains more of the original grain character and flavor, which is essential for single malt whiskey. Distilling to a higher proof would strip away many of the nuanced flavors that define the whiskey.

The distillation process may involve a single or double distillation, depending on the distillery’s preference. Single distillation can retain more of the original grain character, providing a robust and flavorful spirit. Double distillation, on the other hand, can produce a more refined and higher-proof spirit, often resulting in a smoother and more polished final product. Each distillery may choose their method based on the desired flavor profile and style of their whiskey.

The shape and size of the stills also play a crucial role in influencing the flavor of the whiskey. Taller stills generally produce lighter spirits because the longer neck allows for more reflux, where heavier compounds condense and fall back into the pot, while lighter compounds rise to the top. Shorter stills produce heavier, more robust flavors because there is less reflux, allowing more of the heavier compounds to make it into the final distillate. The design of the stills is a key factor in the distillery’s ability to create a unique and distinctive whiskey.

Oak Cask Aging

Oak cask aging shapes the final flavor profile of the whiskey. The type of oak, previous contents of the barrel, and the aging environment all contribute to the unique characteristics of the whiskey.

Many American single malt whiskeys are aged in new American oak barrels. These barrels impart strong flavors of vanilla, caramel, and spice due to the high levels of vanillin and other flavor compounds in the wood. The charring process, which involves burning the inside of the barrel, also plays a significant role in developing these flavors. The charred surface acts as a filter, removing impurities and adding complexity to the whiskey.

Alternatively, used bourbon barrels can be employed for aging. These barrels add complexity and depth from the residual bourbon flavors, such as notes of caramel, toffee, and oak. The previous use of the barrel for bourbon means that some of the harsher tannins have already been extracted, resulting in a smoother whiskey. This method is popular among distillers who seek to create a more nuanced and layered flavor profile.

Some distilleries use a combination of new and used barrels to create a balanced and nuanced whiskey. This approach allows them to harness the bold flavors of new oak while also incorporating the subtle complexities of used barrels. By blending whiskey aged in different types of barrels, distillers can achieve a harmonious balance of flavors.

The aging environment, including temperature and humidity, plays a significant role in the maturation process. Whiskey aged in warmer climates tends to mature faster, developing rich and intense flavors. The higher temperatures cause the whiskey to expand and contract within the barrel, increasing the interaction between the spirit and the wood. This accelerated aging process can result in a more robust and flavorful whiskey in a shorter period.

Bottling

Once the whiskey has reached its desired maturity, must be bottled at a minimum of 80 (U.S.) proof (40% ABV). However, some distilleries choose to bottle at higher strengths, such as cask strength, to preserve more of the whiskey’s natural character. This allows consumers to experience the whiskey in its purest form, often with the option to dilute it to their preferred strength. The bottling process also includes filtering, which can range from minimal to extensive, depending on the distillery’s philosophy. Minimal filtering retains more of the whiskey’s natural oils and flavors, while extensive filtering can create a cleaner, more polished product.

The Future of American Single Malt

The future of American single malt whiskey looks very promising, with more distilleries entering the category and pushing the boundaries of what single malt can be. By embracing traditional techniques and infusing them with their own unique twists, these distilleries are creating whiskeys that stand out on the global stage. American Single Malt has truly come of age.

Resources

American Single Malt Whiskey Commission
americansinglemaltwhiskey.org