“That’s because there is a risk with using this type of yeast. You can do 20 successful fermentations with consistent results, but then that 21st fermentation is totally different.”
Failed sours are still safe to drink, but the taste is not always desirable.
But a common trait in so-called ‘wild ales’ that is surprisingly desirable amongst a small handful of craft brewers in Australia is sourness.
“Sour beer is made with bacteria that is going to drop the PH of the beer,” Mr Boehm said.
“Those bacteria are generally lactic acid-producing bacteria, the ones in yogurt, sourdough and sauerkraut.
There are about 10 craft brewers in Australia specialising in producing sour beers, while about 50 are dabbling in it.
Paul Holgate, from Holgate Brewhouse in Victoria, has a small range of sours, and is collecting bacteria off blackberries in the Macedon Ranges to produce a new line.
“It’s interesting because I spent most of my brewing life trying to keep these critters [wild bacteria] out of the brewing process,” he said.
“I’ve taken some swabs of local blackberries, grown them on plates and tried to make some beer in small lots, although I haven’t commercialised it yet.”
Sour beer is often fermented in barrels because they contain more bacteria and flavours.
This helps Mr Holgate get even more local bacteria into his beer to help it sour.
“A lot of people in the United States are using bourbon barrels because the US has a big bourbon industry, but I prefer to use what is local to me. So we are using pinot noir barrels,” he said.
According to the Brewers Association in the United States, supermarket data shows the sale of sour beer is rapidly increasing, quadrupling from 45,000 cases sold in 2015 to 245,000 in 2016.
“Sales have clearly grow but the full extent is hard to measure because many sours are sold in tasting rooms, breweries or in speciality releases,” Bart Watson, chief economist at the Brewers Association, said.
Wild yeast could be beer equivalent of Champagne
In the same way that premium winemakers rely on the reputation of their growing region to sell their product, like Champagne in France, using wild yeast and bacteria in beer means brewers could soon do something similar.
“You can make a beer that nobody else can make because of your individual local conditions. You can add some of that local ‘terroir’,” he said.
Terroir is a term used in the wine industry to refer to the concoction of environmental conditions, such as climate and soil, that gives wine from a particular region its distinct flavour and smell.
It is the reason Topher Boehm got into the industry.
“We wanted to make a beer that wasn’t just made in a certain place but was actually a product of that place,” he said.
“As an American I was absolutely floored by the beauty of the native flora here in Australia.
“I thought the uniqueness of that would be seen in the microflora [bacteria] here as well.”
Sour beer 2.0
Sour beer — initially an accident — is not new, but is now experiencing a renaissance.
It was the norm hundreds of years ago in Europe when a lack of knowledge about pasteurisation meant brewers struggled to keep out wild bacteria.
Sour beers are still popular in countries like Belgium. However, the sour beers emerging out of Australia and the United States come with a modern twist.
“We are seeing the development of a new type of category with a blurring of lines.”
New brewing techniques are also far from traditional.