The Gnarly Process Of Sour Beers

Sour beers sometimes develop protective pellicles to keep oxygen out.
Skins can form on the surface of beers brewed using lactobacillus, brettanomyces, pediococcus, and other less tame fermentation organisms.

I spent some time yesterday reviewing the fascinating and gnarly pictures of in-production brett beers, wild fermentations, and batches of sour beers started with the dregs of commercial sours on this thread at HomeBrewTalk.

The standard yeasts that most of us use to make beer behave in a very predictable way, but obviously, it wasn’t always so. Sour beers are those where other strains of yeast or bacteria develop. Lactobacillus, best known for converting milk to yogurt and cabbage to sauerkraut, is a prime component in the making of sour beers. In earlier times, beers would have included a more diverse community of fermentation organisms. Lambic is probably the best known sour beer to American drinkers, though the Gose/Geuze style seems to be gaining popularity among craft breweries and drinkers.

Then there’s the funky bunch, the beers brewed partly or wholly with commercial strains of the yeast Brettanomyces. Not necessarily sour beers, brett beers have an extensive list of potential flavor attributes, including such fun descriptors as “barnyard,” and “horse.” In my experience, a brett beer’s flavor, hard to describe though it may be, can be extremely compelling.

The HomeBrewTalk thread linked above is dedicated to images of the pellicle – a thin protective barrier that lacto, brett, pediococcus, and other unusual microbial additions – form as a skin on beers as they sour and age. Apparently the purpose of this surface skin is to protect the microbial community in the beer from oxygen exposure. I’ve never brewed a sour and had no idea that funky beers let their freak flags fly like this. Now that I’ve looked through 100+ pages of images, all I want to do is make a sour and leave a decent amount of headspace to see if I can make a beer so tough it builds its own fortifications.