Beer: Silva Stout Brewery: Green Flash Brewing Co. Style: Imperial Stout ABV: 10.1 percent
It's a good time to own a whiskey distillery in America. Not only are sales of the brown stuff up close to 8 percent from last year and 36 percent over the past five, but you're also making money selling your used barrels to brewers, those nuts. There was a time that the U.S. law requiring "straight bourbon" whiskey be aged in new, unused American oak barrels created a surplus of used wood at distilleries, and in days past these were often sold off on the cheap or just given away. Those days are over. The resale value of a bourbon barrel has skyrocketed, and used barrels are in such high demand among American beer-makers that many distillers now have waiting lists.
Brewers have good reason to covet the barrels. There are several aspects of a used bourbon barrel that can enhance a beer's flavor. First is the wood itself -- American oak is pungent stuff, full of compounds that can impart a kaleidoscope of aromas and flavors. Before a barrel ever reaches a distillery, the inside is often exposed to an open flame and the inner wood is charred. This has the same effect on the wood as a grill has on a steak: sugar in the outer layers caramelizes, producing new, sweet flavors. In oak, charring increases the character of lactones, which come across to our noses as roses or, in higher concentrations, coconut. The heat from charring also breaks down polymers in the wood to form phenolic aldehydes like vanillin, which contributes vanilla-like flavors and is the main ingredient in artificial vanilla flavorings. Other compounds created by the heat can impart flavors and aromas ranging from cinnamon, clove and fresh-baked bread to almond, smoked meat and leather. Yum.
The barrel's previous resident obviously has an impact on beer flavor as well. Oak acts like a sponge, soaking up the liquid within. When a distiller empties a bourbon barrel, a small percentage of the liquid remains behind, trapped in the pores of the wood -- the so-called "devil's cut." As beer ages in the same barrel, some of this trapped whiskey leeches back out, lending the brew booze-like flavors and often a considerable boost in alcohol content. Green Flash Brewing Co.'s Double Stout, for instance, goes into bourbon barrels at 8.8 percent ABV; it comes out at more than 10.
Speaking of Green Flash: the San Diego-based brewery has done its share of gathering those used barrels in the past decade. In 2006, the brewery's barrel aging program consisted of a single red wine barrel filled with Le Freak, an IPA fermented with Belgian yeast. Today, more than 800 wine, bourbon and new oak barrels as well as four 50-barrel foudres (giant oak vats usually used for aging wines or, in the case of breweries, sour ales) are spread across a new, 12,000 square foot facility dedicated to barrel-aging. Cellar 3, as the magical place is known, also has a bottling line that'll be used to package beers in 750-milliliter cork and cage bottles. Soon, sought-after beers like Flanders Drive, Little Freak, Super Freak and Black Freak will each be released into the world. One, Silva Stout, already has been.
Silva Stout, as mentioned above, is what becomes of Green Flash Double Stout after it's aged in bourbon barrels. Named for Green Flash brewmaster Chuck Silva, the brew is actually a blend. After Double Stout is rested in oak bourbon barrels for 18 months, a freshly brewed batch is added to the bourbon-soaked version -- 10 gallons of fresh beer for every 55-gallon barrel of the aged stuff. This balance of fresh and aged flavors may be what led judges to award Silva Stout with a silver medal at the Great American Beer Festival in 2012.
In a snifter, the barrel-aged stout is obsidian. A layer of froth the color and consistency of pancake batter sits atop the stygian liquid. A quick whiff relays notes of cocoa and long-aged whiskey, sure. But give it a swirl and the nose suddenly becomes spicy -- anise, molasses, peppercorns, Fuji apple. It settles into a backdrop of smoky peanuts and charred steak.
According to Silva, most of the bourbon barrels used to age Silva Stout come from Heaven Hill Distilleries in Kentucky, and the sharp notes of whiskey are the first to arrive in the flavor. Beneath that are clear shots of of maple syrup, black licorice, toasted coconut, blackberry and coffee-bean bitterness. The brew's body is much thinner than expected, and though it's nicely cotton-soft, it's almost watery and just too insubstantial for the style. The boisterous alcohol, however, is kept at bay. Oak spices pepper the tongue, but the attendant burn you'd expect from whiskey does not.
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Big bottles of Silva Stout have landed at bottle shops across the Valley. Grab one -- I wouldn't recommend this for aging -- then get to work starting your own whiskey distillery. It's a good investment.