R&D Sour Fruit by New Glarus Brewing Company is part of the brewery’s experimental series of spontaneously fermented fruit sours, produced in very limited quantities and available exclusively from their “Wild Fruit Cave” in Wisconsin. This version is aged in oak barrels and brewed with organic Oregon blackberries, giving it a deep purple hue and an intense, natural fruit aroma.

The process includes fermentation on yeast lees and a secondary bottle fermentation, which creates natural carbonation and a layered, complex flavor profile. With an alcohol content of around 5% and low bitterness (12 IBU), the beer allows the bright acidity and berry character to dominate.

The aroma reveals blackberry, forest fruit, and subtle wild fermentation notes reminiscent of Belgian lambics. The taste is distinctly tart yet balanced by gentle fruit sweetness and a clean, dry finish.

Best served chilled in a smaller glass to fully release its aromatics, it pairs beautifully with soft goat cheese or berry-based desserts. R&D Sour Fruit stands among the most sought-after experimental releases from New Glarus, admired by collectors for its rarity and remarkable depth.