Brewed awakening

There are many ways your favourite beer can turn foul

Every now and then, despite the quality control efforts of many brewers, a bad beer will show up. More often than not, it’s because of a dirty draft line at the local pub or a bottle, especially those clear ones, has sat in the heat or sun, which breaks down a beer’s iso-alpha acids and turns it skunky. You’ll know right away if the latter happens, but sometimes a beer is just bad for a reason that can’t be so readily deduced.

“It happens more than you could possibly imagine, but typically not with more established breweries,” says Roger Mittag, founder of beer education company Thirst for Knowledge Inc. “Keeping equipment clean is one thing, but sometimes bacteria can get in from the environment, sometimes from the canning. There are so many numerous ways that beer can become flawed.”

Generally, the bigger breweries, even the larger craft ones, have fewer issues, while smaller breweries may not have the manpower or expertise to focus on quality control. “Big breweries have lots of money to spend on proper equipment and testing,” Mittag says. “Small brewers just don’t understand or have the coin.”

But even beer from the bigger guys can run into issues since the beverage is very unstable and may change once it is canned, away from prying testers. Mittag says one potential issue is that a beer can liner is very delicate and that can lead to off flavours if subjected to highly acidic beers. “Lots can go wrong in the can, on the shelf,” he says. “It shouldn’t, but it can.”

All beer is acidic to some degree, with the brewing process — malting, brewing and fermenting — bringing a conventional beer’s ph down to 3.7 to 4.1, which is about a thousand times more acidic than neutral water (a ph of seven). Also remember that some beers, particularly sours, a very popular style right now, are intentionally even more acidic. Sour beers are shaped by the hundreds of wild yeasts and bacteria living in them and they produce aromatic compounds that would otherwise ruin a more conventional beer.

But excess acidity is just one of the many ways beer can taste off, Mittag says. A beer that tastes or smells a bit like cat pee? It could be because the beer is stale or a raw material was contaminated. Cheesiness (caused by isovaleric acid) could be due to bacterial infection or poor hop storage.