Heading south out of Blenheim on State Highway 1, there's a large rather sterile looking industrial estate in the suburb of Riverlands.
The estate accommodates a diverse range of businesses, including aluminium and fibreglass fabricators, courier companies, engineering works, food processing companies and a couple of well-known Marlborough wineries.
A few weeks ago I drove out to Riverlands to meet Jason Bathgate, a man whose business card reads "Yeast wrangler & barrel shepherd".
Entering the anonymous-looking warehouse, I was immediately impressed by towering racks of wine barrels and the unmistakable smell of wood and fermentation. But this wasn't one of the province's many winery barrel halls; the columns of wooden casks in this particular warehouse don't contain wine, but maturing beer.
Jason, who trained as a chef in his home state of Vermont in the United States, now works for Marlborough's award-winning 8 Wired Brewing Company where, as well as contract brewing batches of 8 Wired beer at the Renaissance brewery in Blenheim, his job includes the development and management of 8 Wired's growing barrel programme.
While siphoning samples from different casks and making notes, Jason informed me that with about 220 casks filled with a dozen or so different beer styles, 8 Wired could have the largest barrel programme of any brewery in the southern hemisphere.
Barrel programmes? Beers aged in wood?
Such concepts might seem somewhat unusual, but they oughtn't; for centuries brewers, like winemakers, made and stored their products in wooden casks.
According to the American beer writer Randy Mosher, "the invention of the barrel is variously attributed to Bronze Age Celts, Vikings, or similar hairy, cloaked tribes". By Roman times barrels were used across a wide area of northern Europe.
Although wooden barrels served their purpose admirably in pre-industrial times, the difficulty of cleaning and maintaining them was a constant issue. Today, with the exception of a few fiercely traditional British ale brewers, wooden beer barrels have been phased out in favour of more durable metal containers.
However, as Mosher points out, "stainless steel suits the squeaky-clean nature of international lager perfectly, but if you love the funky depths of a truly handmade beer, wood can offer that extra dimension".
But where does that "extra dimension" come from?
The first reason for putting beer into a wooden barrel is to pick up the flavour of the wood itself. Wood contains chemicals which over time dissolve in the beer and add woody, oaky and other flavours. Changes in ambient temperature, such as those from day to night and summer to winter, will cause the beer to seep into and back out of the barrel wall, accelerating the pickup of flavours.
As Mosher explains, "over a period of many months, one of these substances, lignin, transforms into vanillin, which is why vanilla notes are often found in whisky and other barrel-aged spirits".
During my visit to the Riverlands warehouse, Jason gave me a sample of a smoked imperial porter being aged in American oak barrels. Even at just a few months old, the toast and vanilla notes from the barrels adds a remarkable depth of flavour and balance to this hugely intense, roasty brew.
A second reason for storing a beer in wooden casks is to reward it with a mellow aged character. As the wood used in barrel-making is porous, the contents of the cask are slowly exposed to air, resulting in oxidised flavours (which can be both good and bad).
While the majority of beer styles are designed to be consumed as fresh as possible, some darker and stronger ales are excellent candidates for wood ageing. An imperial stout, barley wine or strong wheat beer, for example, might have the potential to age gracefully, but a crisp, golden lager such as a pilsener would be a disaster.
The third reason brewers put beer into barrels is to give the beer some of the character and complexity of what was previously in the barrel. Just as Scotland's distillers age some of their finest single malt whiskies in old sherry and port wine casks, barrels which previously held spirits or fortified wines are especially prized by some adventurous craft brewers.
The Hallertau brewery in Auckland, for example, offers a hugely complex porter that's been aged in pinot noir barrels. But Hallertau's Porter Noir doesn't owe its complexity to just the wine barrels.
Another reason brewers use wooden barrels is as a vessel for further fermentation. The open texture of wood is a natural home for micro organisms, some of which can be beneficial in the brewing and cellaring process.
Belgium's lambic and other sour beer producers, for example, depend on barrels as a safe haven for their wild yeast and bacteria.
Porter noir, for example, gains much of its complexity as a result of an extended fermentation in barrels that have been deliberately infected with the wild yeast Brettanomyces.
In 8 Wired's barrel hall I tasted several different samples of a specially brewed saison which Jason had subsequently run into wine barrels and then inoculated with a cocktail of Brettanomyces, pediococcus and lactobacillus.
With the beer still undergoing a further sequence of fermentation and bacterial activity, the flavour variation between the samples from different barrels was remarkable.
Some were showing a combination of Belgian yeast character and grape notes from the barrels' previous contents, while others were dominated by strong egg-like sulphury fermentation notes. Still more showed strongly alcoholic, spirit-like aromas and flavours.
When the beer is finally deemed ready, Jason will blend components from the different barrels and bottle the beer for release. Limited releases of several barrel-fermented, soured and wood-aged 8 Wired beers can be expected over the coming months and years. They should be easily identifiable in 500ml champagne-style bottles.
My advice is to keep an eye out and buy them when you see them.
- The Marlborough Express