Australian craft brewers have raised the degree of difficulty with an extreme flavour, writes Willie Simpson.
Sour beer is the latest frontier for a handful of adventurous Australian craft brewers. Sourness is usually seen as a fault in beer but in certain styles - notably, Belgian lambic and Berliner Weisse beers - controlled amounts of bacteria are introduced or allowed to form during the production phase, sometimes during extended maturation in wooden barrels.
The degree of difficulty is high and there's a genuine risk ''it might turn into vinegar'', according to a brewer at Wig & Pen, Richard Watkins, whose cherry lambic beer - called Lambs Go Baa - was three years in the making.
It started life as a straightforward ale made from malted barley and wheat, fermented with an English ale yeast. To minimise the risk of cross-contamination, Watkins used his mash tun as an open fermenter.
On the third day of fermentation he moved the brew into a 500-litre oak puncheon and added a wild yeast culture, Brettanomyces bruxellensis. The beer spent 18 months ageing in the barrel, during which time Watkins added 300 kilograms of cherry pulp, part of a parcel of hailstone-damaged fruit sourced from Young in December 2010.
''A lot of the [cherry] sweetness gets converted into alcohol,'' he says. ''I tasted it progressively and you're always worried about keeping something in wood this long. But you've got to give it a go.''
Watkins added another 30 kilograms of cherry pulp just before kegging the beer. ''I wanted to give it a bit of sweetness,'' he says. ''I didn't want to shock punters who'd never tasted a lambic before.''
Lambs Go Baa is considerably higher in alcohol than most Belgian fruit lambics.
''I wanted to give it a bit of protection and to fill out the palate. I wouldn't do it any different,'' says Watkins, who has a few other lambic brews at varying stages of development. Lambs Go Baa sells on tap at the Wig & Pen in Canberra for $9 each 235-millilitre brandy balloon.
Based in Evandale, in north-east Tasmania, Will Tatchell from Van Dieman Brewing has created a novel sour twist to the second release of Hedgerow, his autumn seasonal beer. This amber ale incorporates hawthorn berries, sloe berries and rosehips, harvested from his family property after the first winter frost, and added to the conditioning beer throughout a period of 12 weeks.
For this year's batch, Tatchell matured a portion in wine casks that previously held Moores Hill pinot noir, and the wood has imparted some distinctly feral and sour characters to the final beer.
''There are certainly some aromatic French oak qualities coming through on the nose, as well as a few spicy notes,'' Tatchell says. ''The barrel-aged element brings that funky edge to the beer, as well as the imparted tartness.
''The initial sip is quite sour and sharp but, as you work through the beer, a ripe sweetness begins to develop and reflects the original Hedgerow beer.''
There's no doubt sourness in beer is a fairly extreme flavour element but, in both beers reviewed, it adds a challenging layer of complexity that will appeal to certain palates out there.