Pop Quiz: what’s Kentucky’s biggest foreign export? Horses? Bourbon? Coal?
Nope. It’s barrels.
Specifically, used bourbon barrels. Most are shipped to Scotland where distillers use them to age scotch. Fifteen years ago, there weren’t too many other people interested in buying the used barrels. But since then they’ve come into vogue. Suddenly it seems like everything is being aged in them: beer, cider, gin, maple syrup, hot sauce, coffee, even honey. In some cases it’s mostly a marketing stunt: people take ready-made products, store them in a barrel for a while and then sell them with a clever name and a hefty markup. But there are a few companies out there who make really good food that tastes even better after being aged in bourbon barrels. One of the best ones I know of is Matt Jamie’s Bluegrass Soy Sauce.
Matt, a Kentucky native, was inspired to make his soy sauce after noticing the similarities in how soy sauce and bourbon are made.
Both start with grains: bourbon is typically a mix of corn, barley, and rye, while traditional soy sauce starts with soybeans and wheat. The soy Matt selects is non-GMO and grown in Kentucky. Making both products starts with cooking the grains in water. The next step for both products is to ferment the grains. From there the production differs: the bourbon mash is distilled, the soy mash is added to a super salty brine. Traditionally in Japan the brine would have been seawater; Matt makes his brine with sea salt and filtered limestone Kentucky water (the same water many bourbon makers use in their own products). After that the production is similar again: both are aged in barrels for a long time. Bourbon must be aged for at least two years, and most commercial soy sauce is aged for several months. Traditional soy sauce in Japan is often aged in barrel-sized earthenware jars, though these days big producers choose to age their soy sauce in ginormous metal tanks. Matt ages his soy sauce for a full year in used Woodford Reserve barrels.
There are a few things that make bourbon barrels so popular: the oak, the char, and the (relatively) steady supply.
Bourbon barrels have been made of oak for more than 200 years. Early bourbon distillers probably chose oak because it was plentiful in the local Kentucky hills and it bends relatively easily to make good, strong barrels. At first, the bourbon was made for home use, and it would have been drunk fairly soon after it was made. The barrel was just a convenient place to store the clear, somewhat harsh liquor. But as folks started selling the bourbon it spent more time in the barrels as it shipped to the buyers. People noticed that after aging for several months in those oak barrels, the bourbon changed: it gained a golden color and a smoother, richer, more complex flavor. In wine, oak is a source for sweet, woodsy notes often compared to vanilla.
Around the same time, a Kentucky reverend named Elijah Craig started charring the inside of the barrels he used to age his bourbon. The reason why he charred them has been lost to history: maybe he had some barrels that were burned in a barn fire and he didn’t want to throw them out, or maybe he was reusing old barrels and burned the inside to destroy any leftover flavors of previous contents, or maybe he was a visionary who knew that charred barrels would make great tasting bourbon. Who knows. Whatever the motivation, he discovered that the charred barrels imparted delicious smoky, caramel notes to the bourbon. Coopers have been blackening them ever since.
To get the full effect of the charred oak flavor, bourbon must be aged in brand new barrels. In order to keep up with bourbon demand, that means that hundreds of thousands of new bourbon barrels are made every year. That also means that each year, as bourbon is bottled, there are hundreds of thousands of used barrels for sale.
The time Bluegrass soy sauce spends in those bourbon barrels adds a lot to its flavor.
Most soy sauce is fairly harsh and doesn’t offer a ton of flavor beyond being intensely, almost painfully salty. Bluegrass soy sauce is salty, of course, but it’s also toasty, brothy, smoky, with some floral and vanilla notes—a lot of which is contributed by the barrel. There are even some subtly oaky, softly sweet notes that hint at the flavor of bourbon. Using Bluegrass soy sauce in your cooking adds a lot more complexity than its grocery store counterparts. Beyond sprinkling it over stir fry and sushi, try adding a dash to mushroom risotto: it adds a great savory depth of flavor in a flash.