Sour beers account for an estimated 5-6% of the global craft beer market. In 2023, the sour beer market was valued at approximately $4-5 billion USD. Growth in the sour beer market is expected to outpace the broader craft beer sector, with some estimates projecting a CAGR of 10-12% over the next five years as the style gains popularity.[1]
Primary Souring (Sour-Fermented)
Primary souring reduces the risk of off-flavours by excluding bacteria, which lowers the chance of unwanted flavours from wild or spontaneous fermentation. This method can produce a final product that appeals to a broader audience, avoiding the more complex, funky, or earthy notes typical of traditional souring methods. The reduced cross-contamination risk also makes it safer for breweries producing a variety of beer styles, as it allows them to use the same equipment without fearing bacterial contamination.
This method also supports simpler cleaning protocols and consistency across batches, making it particularly beneficial for breweries aiming for consistent quality and flavour across multiple batches.
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Spontaneous fermentation
This approach offers several advantages, including a complex flavour profile and the potential for aging, which adds depth and refinement. Similar to wine, it encapsulates a sense of terroir, allowing the beer to reflect the unique character of the region or the specific environment of the brewery, resulting in a one-of-a-kind product that is deeply tied to a particular place.
However, this technique presents several challenges. Unpredictability is a significant issue, as the quality and consistency of flavours can vary from batch to batch due to the random nature of the microbial activity. To maintain consistency, brewers may use methods like "back-slopping" or a "house culture," but these methods can lead to microbial drift over time, altering the beer’s character. Contamination risk is another concern, as spontaneous fermentation is susceptible to undesirable bacteria or wild yeasts that can spoil the beer. Additionally, seasonal constraints may limit production, as this method often depends on specific environmental conditions, such as temperature and humidity
Through this process, Brouwerij Boon (Belgium) produces their Oude Geuze a spontaneously fermented beer in cooling vessels and then matures 100% in oak barrels [2]
Sour Malted
Through this process, brewers get greater consistency and control over the acidity and sourness in the final product. The malting process allows for adjustment of the malt’s acidity, resulting in a more predictable sour flavour. Unlike spontaneous fermentation, which introduces various wild organisms, sour malting produces cleaner sour notes without the earthy or funky flavours associated with wild bacteria. The reduced risk of contamination at the malting stage also minimises the need for separate equipment or rigorous cleaning protocols.
However, this technique has drawbacks. Pre-soured malt can increase upfront production costs, and the process may lack the depth and complexity found in more traditional sourcing methods, such as wild fermentation or barrel aging
Using acidulated malt Westbrook Brewing Co. (USA) is very well known for its Gose, in their own words ‘Sour, salty, delicious’. [3]
Kettle-Souring
This is a fast and controlled process that allows brewers to sour a beer in days rather than months or years. This technique offers significant control over acidity levels by enabling precise pH monitoring during the souring process. It is also Cost-Effective and simpler than long-term barrel aging or spontaneous fermentation, making it more accessible for brewers with limited resources.
However, kettle souring comes with potential challenges, such as the risk of Off-Flavors (e.g., yogurt-like or cheesy notes) if the Lactobacillus is not carefully managed or if the wort is held at the wrong temperature for too long. Additionally, the souring process can tie up brewing equipment, limiting production capacity, which may be a concern for smaller breweries.
Anderson Valley Brewing Co. (USA) has several styles from their Gose series done through this process, e.g. Blood Orange Go, Cherry Gosese etc. [4]
Mixed Culture Fermented Sours
This process allows for the development of a diverse range of flavours, from fruity and tart to funky and earthy. The combination of yeast and bacteria creates more complexity than single-culture fermentation, with flavours that evolve over time. As the beer ages, the microorganisms interact and contribute to its evolving profile, resulting in more refined and nuanced characteristics.
This method is versatile, and suitable for various sour beer styles. However, it can introduce unpredictable and inconsistent results due to the varying behaviour of wild yeasts and bacteria, leading to challenges in achieving quality assurance and consistency. The risk of off-flavours is higher, and the method requires longer production time due to extended fermentation and aging periods, which can delay return on investment.
Jester King Brewery (USA) are pioneer in farmhouse ales and souring techniques, as they express for their Le Petit Prince Farmhouse Table Beer, a ‘ beguiling yeast character that only wild fermentation with native yeast can create’. [5]
Soured maturation in wooden barrels
This approach provides the complex flavours , driven largely by the microbial activity that wooden barrels contain. The porous nature of the wood encourages the growth of various microbes, including Brettanomyces, Lactobacillus, and Pediococcus, which contribute to a diverse range of sour, funky, and earthy flavours. Beyond the microbial influence, the barrels themselves impart subtle characteristics such as vanilla, tannins, and spices, further enhancing the beer’s profile.
The slow oxygen permeability of the wood aids in mellowing the beer over time, reducing sharp acidity and fostering the development of deeper, more rounded flavours.
Despite these benefits, barrel maturation introduces variability due to the natural differences in the wood and its resident microbes, leading to potential inconsistencies between batches. Additionally, the process is time-intensive, often requiring months or even years to achieve the desired outcomes, which can prolong production cycles and place a strain on resources.
Russian River Brewing Company (USA), matures several of their awarded beer in wood barrels, e.g. Supplication and Consecration. [6]
Ana Victoria Vasquez de la Peña
ana@neumaker.com.au
30 August 2024