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Wednesday, 01 June 2011 13:00

Mystery of the Canadian Whisky Fungus

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A scanning electron microscope image (500X) of the mold found outside the Hiram Walker Distillery.
Photo: Caren Alpert

The air outside a distillery warehouse smells like witch hazel and spices, with notes of candied fruit and vanilla—warm and tangy- mellow. It’s the aroma of fresh cookies cooling in the kitchen while a fancy cocktail party gets out of hand in the living room.

James Scott encountered that scent for the first time a decade ago in a town called Lakeshore, Ontario. Just across the river from Detroit, Lakeshore is where barrels of Canadian Club whiskey age in blocky, windowless warehouses. Scott, who had recently completed his PhD in mycology at the University of Toronto, had launched a business called Sporometrics. Run out of his apartment, it was a sort of consulting detective agency for companies that needed help dealing with weird fungal infestations. The first call he got after putting up his website was from a director of research at Hiram Walker Distillery named David Doyle.

Doyle had a problem. In the neighborhood surrounding his Lakeshore warehouses, homeowners were complaining about a mysterious black mold coating their houses. And the residents, following their noses, blamed the whiskey. Doyle wanted to know what the mold was and whether it was the company’s fault. Scott headed up to Lakeshore to take a look.

When he arrived at the warehouse, the first thing he noticed (after “the beautiful, sweet, mellow smell of aging Canadian whiskey,” he says) was the black stuff. It was everywhere—on the walls of buildings, on chain-link fences, on metal street signs, as if a battalion of Dickensian chimney sweeps had careened through town. “In the back of the property, there was an old stainless steel fermenter tank,” Scott says. “It was lying on its side, and it had this fungus growing all over it. Stainless steel!” The whole point of stainless steel is that things don’t grow on it.

Standing at a black-stained fence, Doyle explained that the distillery had been trying to solve the mystery for more than a decade. Mycologists at the University of Windsor were stumped. A team from the Scotch Whisky Association’s Research Institute had taken samples and concluded it was just a thick layer of normal environmental fungi: Aspergillus, Exophiala, stuff like that. Ubiquitous and—maybe most important—in no way the distillery’s fault.

Scott shook his head. “David,” he said, “that’s not what it is. It’s something completely different.”

Leave fruit juice on its own for a few days or weeks and yeast—a type of fungus—will appear as if by magic. In one of nature’s great miracles, yeast eats sugar and excretes carbon dioxide and ethanol, the chemical that makes booze boozy. That’s fermentation.

If fermentation is a miracle of nature, then distillation is a miracle of science. Heat a fermented liquid and the lighter, more volatile chemical components—alcohols, ketones, esters, and so on—evaporate and separate from the heavier ones (like water). That vapor, cooled and condensed into a liquid, is a spirit. Do it to wine, you get brandy; beer, you get whiskey. Distill anything enough times and you get vodka. When it’s executed right, the process concentrates a remarkable array of aromatic and flavorful chemicals.


Photo: Caren Alpert

The basic technology of distillation—a still—consists of a tank for heating and a long tube that carries away the distillate to a receiving vessel. That simple design dates to somewhere between the first and third centuries AD, to the Alexandria lab of Maria the Jewess, one of the great Hellenistic alchemists. Maria and her colleagues were more interested in the secrets of life and the transmutation of elements than in getting wasted. They were trying to distill the “spirits” inherent in nature. Chinese apothecaries started making a potent, rough spirit as early as 670. But in the West, it wasn’t until the Middle Ages that anyone really started thinking about drinking hard alcohol; physicians in Salerno first tippled distilled wine in the mid-1100s. The technology kept improving: The famed Murano glassworks in Italy provided carefully engineered tubing and better glassware for allowing distilled vapors to cool and condense. Even Leonardo da Vinci worked on a still furnace design. By the late 1600s, most of Europe was smashed on cheap Dutch gin, French brandy, and corn spirits.

Distillation was literally a transformative technology. If you were a farmer, you could harvest all that grain or fruit and distill it down to a few easy-to-transport barrels of liquid. The product never spoiled and was worth more at market than the grain or fruit itself. The economics made a lot of sense.

By the 18th century, aging spirits in barrels for a few years had become standard practice. Exposure to oak improved the final product—coopers use heat to make casks, breaking down structural lignin, cellulose, and hemicellulose into weird, interesting sugars that dissolve into the spirit. Depending on humidity and temperature (and on whether the wood is American or European oak), tannins, sweet vanillin, smoky phenols, coconutty oak lactones, and dozens of other similar molecules also leach in. Meanwhile, some of the ethanol oxidizes, eventually yielding ethyl acetate, which imparts a smoother flavor. After a few years, what comes out of those barrels is awfully compelling. American whiskey makers were selling aged booze as early as 1793, and brandy from the French region of Cognac typically spent a year or two in a barrel, too.

But that improvement came at a price. Aging meant losing some of the product to evaporation, through pores in the wooden casks. That loss is called, evocatively, the angels’ share—a portion of spirit offered up to heaven in thanks for a miracle. It’s no small thing: Whiskey makers calculate it at 2 percent a year by volume, which amounts to 18 percent over 10 years. (Of course, that evaporation also concentrates everything left inside, improving flavor.)

This new stage in the manufacturing cycle took the business of spirits to a new level. Now distillers needed real estate to warehouse the casks, and they needed a robust credit economy to fund the manufacture of a product that wouldn’t be sold for years. At the same time, a leisure class had to emerge that would pay a premium to drink something more refined than moonshine.

In other words, the birth of the economic ecosystem surrounding aged liquor represents a signal moment in the early Industrial Revolution, a mile marker on the road to a more civilized world. And somehow that fungus staining the walls of Lakeshore was a byproduct of that journey.

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