Sometimes how brewers take for granted how big of an impact yeast makes on a beer. It seems like the grain bill and the hops garnish the lion share of attention, but the truth is that the yeast can play just as large of a role in certain beers. This is especially true with sours, lambics, gueuze and wild ales. One of the main yeast stains commonly used with wild ales and sours is brettanomyces or also commonly called brett.
Brettanomyces is very special because in addition to converting sugars to alcohol and CO2, it also creates a high amount of acetic acid and off flavors in certain environments. Brett or Brettanomyces is often described as adding a funky or horse blanket like flavor to beer and as you can imagine, in most cases is undesirable. It is important to note that if you are going to dabble in the use of brettanomyces or other souring bacteria such as lactobacillus and pediococcus you will want to consider setting aside specific equipment such as fermenters, kegs and racking canes for your wild ales and sours. Once these yeasts and bacteria come in contact with your fermenting equipment they can be more difficult to eradicate than typical brewing yeast strains due to their ability to survive in high temperatures, tolerate high alcohol levels and their ability to survive in low pH environments. If not, it is very important to make sure that you practice proper cleaning and sanitization methods to insure you will not contaminate future batches of beer.
Recently Brettanomyces has made become very popular in alternative beer styles. It is a powerful tool to have for a creative brewer who is working on designing interesting and flavorful beers. It is also an important reminder of just how important both yeast and fermentation conditions are in creation of a beers taste.
If you are looking to taste examples of well crafted brettanomyces beers, I highly recommend Russian River Sanctification which is a 100% brett beer and also any one of the Crooked Stave 100% brett release beers.