Making sour beer is a fascinating process that involves a unique approach to fermentation. There are two main methods used to create sour beer: spontaneous fermentation and mixed fermentation.
Spontaneous fermentation is a traditional method that relies on the wild yeast and bacteria present in the air. It begins by exposing the wort, which is the unfermented beer, to the open air in a large, shallow vessel called a coolship. This vessel allows the wort to cool overnight and collect microorganisms from the environment. The next day, the wort is transferred to oak barrels or other fermentation vessels where it continues to ferment and sour over an extended period of time, often months or even years.
I have had the privilege of witnessing a spontaneous fermentation firsthand during a visit to a traditional lambic brewery in Belgium. The brewmaster explained that the coolship is positioned in a specific area of the brewery, where it can absorb the unique microorganisms present in the local air. This creates a distinct flavor profile that is characteristic of the region.
On the other hand, mixed fermentation involves intentionally introducing specific yeast strains, such as brewer's yeast and brettanomyces, as well as bacteria, into the wort. This method provides more control over the fermentation process and allows brewers to achieve desired flavors and acidity levels. The yeast strains and bacteria work together to create complex flavors and aromas, resulting in a sour beer with depth and character.
During my time as a brewer, I experimented with mixed fermentation techniques to create sour beers. One particular batch involved pitching a blend of brewer's yeast, brettanomyces, and lactobacillus into the wort. The initial fermentation with the brewer's yeast provided the base alcohol, while the brettanomyces and lactobacillus contributed to the souring process. The beer was then aged in oak barrels for several months, allowing the flavors to develop and mature.
The aging process is a crucial component in making sour beer. It allows the flavors to evolve and develop over time. During this period, the microbes continue to work their magic, breaking down complex sugars and creating unique flavors and aromas. The length of aging can vary depending on the desired style and the brewer's preference.
In addition to the fermentation process, the choice of ingredients also plays a significant role in creating sour beer. Brewers often use a blend of malted barley and wheat to provide a solid base for the fermentation. Hops are typically used sparingly in sour beers as their bitterness can clash with the sour flavors. Instead, brewers may opt for aged hops, which contribute to the beer's complexity without overpowering the sourness.
To summarize the process of making sour beer:
1. Spontaneous fermentation involves exposing the wort to the wild yeast and bacteria present in the air using a coolship. The wort is then transferred to barrels for aging.
2. Mixed fermentation involves intentionally introducing specific yeast strains and bacteria into the wort to achieve desired flavors and acidity levels. The beer is then aged to allow the flavors to develop.
3. Aging is crucial in creating sour beer, allowing the flavors to evolve and develop over time.
4. The choice of ingredients, including malted barley, wheat, and aged hops, contributes to the overall flavor profile of the beer.
Making sour beer is a labor of love that requires patience and a willingness to embrace the unpredictable nature of fermentation. The end result is a unique and complex beverage that delights the senses and showcases the artistry of the brewer.