We/PM had the immense honor to get schooled today by Todd Leopold, one of the most knowledgeable distillers we got to meet. Below is a recap of one of the many bits of deep info he shared with the team.
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From the early 20th century until 1962, the standard entry proof for American whiskey was consistently set at 50%. This entry proof, or the alcohol content at which whiskey is put into barrels for aging, played a crucial role in shaping the character and quality of the final product. A significant reason for this standard was that a lower entry proof contributes to a softer, more refined whiskey. This effect is particularly notable after the whiskey has aged for several years.
Historical data, such as studies conducted by the IRS, reveal that the proof of whiskey in Kentucky warehouses typically increased from 50% to about 107 proof over an eight-year period. This gradual rise in proof necessitates only minimal dilution with water to achieve the desired bottling strength, thus preserving the complex flavors and aromas developed during aging. In contrast, starting with a higher entry proof, such as 62.5%, results in a much more concentrated spirit that can climb into the high 60s or even 70s in proof. Diluting this high-proof whiskey to bottling strength requires adding significant amounts of water, which can dilute the flavors and aromas meticulously developed during maturation.
A lower entry proof also impacts the extraction of compounds from the wood of the barrel. Whiskey aged at higher proofs tends to pull out more aggressive tannins and wood flavors, sometimes described as pencil shavings or furniture-grade wood. These characteristics can overpower the subtler notes and lead to a harsher tasting whiskey. Conversely, whiskey aged at the traditional 50% entry proof extracts fewer of these intense compounds, resulting in a smoother, more balanced spirit.
The legislative and regulatory changes over time have also influenced whiskey production practices. In the early 1960s, lobbying efforts led to an increase in the maximum legal entry proof from 55% to 62.5%. Prior to this change, few distillers utilized the 55% maximum, instead adhering to the lower proofs. The rationale behind these regulatory shifts was largely economic. By allowing higher entry proofs, distilleries could produce more whiskey with fewer barrels, thereby reducing costs associated with storage and production. This change, however, was not driven by considerations of quality but rather by financial imperatives during a period when many distilleries were struggling to remain operational.
Another critical factor in whiskey aging is esterification, the chemical reaction that forms esters, which contribute to the fruity and floral notes in whiskey. Lower alcohol content during aging facilitates greater oxygen absorption, enhancing esterification reactions. Experimental data, although not extensive, suggests that whiskey aged at lower entry proofs (such as 50%) tends to develop higher levels of esters compared to those aged at higher proofs. This interplay between organic acids and esters is crucial during the aging process, particularly in the initial four years. Studies have shown that these components evolve together, reaching a harmonious balance that signifies maturity.
The historical context provided by documents such as the Crampton and Tolman study illustrates the meticulous approach to understanding whiskey production. This study surveyed 31 distilleries, analyzing variables like mash bill, warehouse conditions, and aging samples over eight years. It established that the standard entry proof was around 100 proof, with minor variations. Subsequent studies during Prohibition confirmed these findings, underscoring the consistency in production practices despite economic pressures.
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Yeah, Todd is VERY good.