Michter’s Distillery employs six key production tenets to create its renowned whiskies. The first tenet is to air-dry the white oak used for its barrels for a minimum of 18 months. This essential step aids in breaking down compounds that could make the whiskey taste woody and bitter. Following this, the second tenet involves toasting the barrels before charring them. This process enhances flavor compounds, including vanillin, which imparts a distinctive vanilla character to bourbon. The third tenet concerns barrel entry proof.
Heat-cycled warehousing is the fourth tenet, which affects how whiskey interacts with the barrel. The fifth tenet specifies that each whiskey expression has its own chill filtration protocol, ensuring unique flavor characteristics. Lastly, the sixth tenet states that Michter’s bourbons and ryes are bottled as either single barrel or small batch whiskies.
The interaction between whiskey and the barrels during aging is complex. Toasting and charring the barrel interiors caramelizes a variety of wood sugars, producing flavors absorbed by the whiskey as it soaks in and seeps out of the wood. Deeper charring facilitates this movement, creating fissures in the wood that increase the exposed surface area. Because water is a smaller molecule than ethanol, it moves more easily through the wood, and its superior properties as a solvent allow it to dissolve more flavor compounds, enhancing the overall profile of the spirit. Andrea Wilson, Michter’s chemist, master of maturation, and chief operating officer, elaborates on the importance of these processes: “If you’ve ever tasted a whiskey that’s over-oaked, you likely picked up an astringency, dryness, and bitterness caused by the wood’s polyphenolic compounds, commonly referred to as tannins or wood sugars. While phenols bolster the flavorful esters, an excess can create unwanted wood notes. Water is a powerful agent for breaking down compounds. When you add water, phenolic compounds become soluble. Once dissolved, they can oxidize, resulting in a smoother whiskey.” Wilson explains. “The easiest way to think about it is that when you toast a barrel, you soften the tannins in the wood. Lowering the entry proof of the spirit and adding additional water allows the phenolic compounds to dissolve into solution. Then, as the barrel breathes in oxygen, it oxidizes the dissolved compounds, resulting in a much smoother whiskey due to the chemical changes of the astringent compounds. Wilson likens this process to decanting wine, where allowing the spirit to breathe enhances its flavors.
In a blind tasting of two whiskies at the same proof—one put in the barrel at 103 proof and the other at 125 proof, the maximum allowed as outlined in the federal standards of identity for making bourbon—the lower entry proof bourbon exhibited a richer mouthfeel and a slight chocolate note, while the higher entry proof whiskey had caramel but no chocolate notes.
The ratio of alcohol to water in the new make introduced to the barrel is just one of many factors that affect flavor, and this ratio has evolved over time. In the 19th century, before glass bottles became widely available, most whiskey was sold in barrels. Customers brought their own containers to shops, which were filled from barrels that were typically only two or three years old and filled between 100 and 103 proof. The proof could fluctuate during aging, so by the time it was purchased, it often ranged between 95 and 105 proof. This relatively high water content allowed young whiskey to absorb more caramelized wood sugar flavors.
As the century progressed and glass bottles became mass-manufactured, entry proof rose to about 107 proof, resulting in aged products typically bottled at around 100 proof. After Prohibition, the Federal Alcohol Administration Act of 1935 set the upper limit on entry proof at 110, and in 1962, it was raised to today’s 125 proof.
Shortly after this regulatory change, two Seagram chemists studied the significance of barrel entry proof. Their findings, published in the 1974 Journal of the Association of Official Analytical Chemists, revealed that as barrel entry proof increased, bourbon’s color intensity and congener concentration—which reflect the beloved caramels, vanillas, and baking spices in American whiskey—decreased.
Since new make comes off the still at no higher than 160 proof, distillers need to add less water to achieve 125 proof than to reach a lower proof. After aging, even more water can be added if bottling at 100, 90, or the lowest bottling proof of 80. This means that higher entry proof can yield more bottles of whiskey per barrel, a factor worth considering when calculating profit margins. Despite these economic advantages, many distillers choose a lower barrel entry proof, often prioritizing flavor over yield.
Climate also plays a crucial role; in a dry climate at high elevation, water evaporates faster than alcohol as the spirit matures, leading to higher barrel proof. For instance, whiskey barreled at 125 proof might end up at 135 to 140 proof after three or four years, which can result in harsher barrel and wood flavors.
Ultimately, a higher barrel entry proof extracts more alcohol-soluble compounds, such as aromatic aldehydes, coumarins, and terpenols, while a lower entry proof extracts more water-soluble compounds like wood sugars and trace solids, enhancing sweetness and body. The goal is to strike a balance between these different types of congener extraction.
DISTILLER PROOFS*
Four Roses: 120 barrel entry proof
Wild Turkey: 115 barrel entry proof
W.L. Weller/Van Winkle: 114 barrel entry proof
Maker’s Mark: 110 barrel entry proof
Peerless: 107 barrel entry proof
MB Roland: 105 barrel entry proof
Michter’s: 103 barrel entry proof
Comments