Single barrel. Bottled at proof (120122). Japanese Umeshu cask finish. The sixth Boss Hog and the first American whiskey ever finished using koji fermentation.

WhistlePig’s Boss Hog series raises the bar with each edition. The Samurai Scientist sixth in the series is a genuine first in American whiskey history: finished in casks from Kitaya brewery on Japan’s Kyushu island using Umeshu, the traditional Japanese plum wine. The collaboration with Kitaya also introduced koji fermentation to the production process an ancient Japanese technique that had never been applied to American whiskey before this release.

The bottle honors Jokichi Takamine, the Japanese-American chemist who pioneered koji fermentation in the American whiskey industry over a century ago a scientist ahead of his time, working at the intersection of two whisky cultures. That story is what gives this release its name and its significance beyond the liquid itself.

Tasting Notes

• Appearance: Deep amber with warm mahogany notes.
• Aroma: Distinctly complex ripe plum, warm rye spice, subtle floral notes, and a delicate umami undertone from the koji influence.
• Palate: Powerfully complex the bold rye grain base meets plum fruit and a subtle savory depth that no other rye whiskey delivers. Unique in every sense of the word.
• Finish: Long and evolving warm spice, dried fruit, and a lingering Japanese oak character.

The Koji Connection

Koji (Aspergillus oryzae) is a mold used in the production of sake, miso, and soy sauce and a cornerstone of Japanese fermentation culture for over a thousand years. Jokichi Takamine introduced it to American distilling in the 1890s, believing it could improve whiskey production. His work was largely abandoned. WhistlePig’s collaboration with Kitaya revives that legacy in the most direct way possible: an American rye finished in casks from a Japanese brewery built on koji tradition.

Specs

• Distillery: WhistlePig Farm, Shoreham, Vermont
• Style: Straight Rye Whiskey
• Finish: Japanese Umeshu casks, Kitaya Brewery, Kyushu, Japan
• Bottling: Single barrel, bottled at proof (120122)
• Size: 750ml
• Release: Boss Hog 6th Edition

Explore the full WhistlePig collection or browse all rye whiskey at Wooden Cork.

Frequently Asked Questions

• What is Umeshu and how does it affect the whiskey? Umeshu is a traditional Japanese liqueur made by steeping ume plums in shochu or sake with sugar. The residual plum fruit, sweetness, and subtle acidity in the casks impart ripe plum notes, a delicate floral character, and a complexity that has no parallel in Western cask finishing traditions.
• Who was Jokichi Takamine? Jokichi Takamine (18541922) was a Japanese-American chemist who made foundational contributions to both pharmaceutical science and American distilling. He pioneered the use of koji fermentation the same enzyme-based process central to sake and miso production in American whiskey production, decades before its broader adoption. Boss Hog VI honors his legacy directly.
• How does Boss Hog VI compare to Boss Hog V (Spirit of Mauve)? Boss Hog V used Calvados (French apple brandy) casks for a fruit-forward, Western European profile. Boss Hog VI uses Japanese Umeshu casks and introduces koji fermentation a fundamentally different direction that produces a more exotic, savory-inflected complexity. Both are single barrel, bottled at proof, and unrepeatable.
• Is WhistlePig Boss Hog VI a limited release? Yes each Boss Hog edition is single barrel and produced in strictly limited quantities. The Samurai Scientist is not an ongoing expression and will not be restocked once sold out.

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