What are sour beers?
Sour beers are alcoholic beverages made from barley and wheat in the same way that beer is. But by using microorganisms other than brewers yeast these beers have a higher acidity and a drier finish. These can be crisp and refreshing, like a traditional lemonade, or complex, like a red wine. Are you ready to explore the fascinating world of sour beers? These complex brews have a long history and have been gaining cult popularity in the craft beer scene, and for good reason. Let's dive into some of the aspects of sour beer production for all levels of beer enthusiasts.
The Microbial Magic Behind Sour Beers
Unlike conventional beers that rely on carefully controlled fermentation with specific Saccharomyces yeast strains, sour beers embrace a more diverse microbial ecosystem. This includes:
- Saccharomyces: Brewers yeast makes alcohol and flavour compounds.
- Lactobacillus: A bacteria that produces lactic acid, contributing to a clean, tangy sourness.
- Pediococcus: Another lactic acid-producing bacteria, often responsible for more complex, funky flavours.
- Brettanomyces: A wild yeast that can produce acetic acid and various esters, adding fruity and funky notes.
The Biochemistry of Sourness
The sourness in these beers primarily comes from organic acids produced during fermentation:
- Lactic acid: Contributes a clean, yoghurt-like tartness
- Acetic acid: Adds a vinegar-like sharpness (suitable in beer in small amounts)
- Citric acid: Provides a lemony zing (often from fruit additions)
pH levels in sour beers typically range from 3.0 to 3.5, compared to 4.0 to 4.5 in conventional beers.
Sour Beer Production Methods
- Kettle Souring: Typically used for Berliner Weiss and Gose
- Fast-track method using Lactobacillus to sour the wort before boiling
- Allows for more control and consistency
- lower risk of contaminating other beers
- pH typically drops to 3.2-3.5 within 24-48 hours
- Mixed Fermentation: Typically used for American wild/sour beers
- Involves pitching a combination of Saccharomyces, Brettanomyces, and other bacteria
- Longer fermentation period (months to years)
- Results in more complex flavour profiles
- Spontaneous Fermentation: Characteristic of Gueuze, Lambic, Flanders Red, Oude Bruin.
- Wort is exposed to ambient microbes (traditionally in a coolship)
- Highly unpredictable but can produce unique, terroir-driven beers
- Often blended to achieve consistency
Typical Aspects of Sour Beer Styles
Gueuze:
A very refreshing, highly carbonated, pleasantly sour but balanced wild Belgian wheat beer. The wild beer character can be complex and varied, combining sour, funky, and fruity flavours.
- A blend of young (1-year-old) and aged (2-3-year-old) lambics
- Secondary fermentation in the bottle creates natural high carbonation
Lambic:
A fairly sour, often moderately funky, wild Belgian wheat beer with sourness taking the place of hop bitterness in the balance. Traditionally served uncarbonated as a café drink.
- Spontaneously fermented using a turbid mash process (more information on this process, view our article The Turbid Mash: Unlocking the Secrets of Sour Beer Brewing)
- Aged hops (1-3 years old) used to prevent spoilage
- Fermented and aged in oak barrels for 1-3 years
Fruit Lambic:
A complex, refreshing, pleasantly sour Belgian wheat beer blending a complementary fermented fruit character with a sour, funky Gueuze.
- Spontaneously fermented using a turbid mash process
- Aged hops (1-3 years old) used to prevent spoilage
- Fermented and aged in oak barrels for 1-3 years
- Common fruits added: Cherry (Kriek), Raspberries (Framboise)
Flanders Red:
A sour and fruity oak-aged reddish-brown Belgian-style ale with supportive toasty malt flavours and fruit complexity. The dry, tannic finish supports the suggestion of a vintage red wine.
- Mixed culture fermentation with extended oak ageing (up to 2 years)
- Often blended with younger beer for balance
- Final pH: 3.2-3.5
Oud Bruin:
A malty, fruity, aged, somewhat sour Belgian-style brown ale with a caramel-chocolate malt flavour and often substantial alcohol.
- Mixed culture fermentation with extended ageing, often in stainless steel
- Often blended with younger beer for balance
Berliner Weisse:
A very pale, refreshing, low-alcohol German wheat beer with a clean lactic sourness and a very high carbonation level. A light bread dough malt flavour supports the sourness, which shouldn’t seem artificial. A gentle fruitiness is found in the best examples.
- Traditionally uses a symbiotic culture of Saccharomyces and Lactobacillus
- High wheat content (up to 50% of the grist)
- Highly attenuated with a final gravity of 1.003-1.006 for a dry finish.
Gose:
A tart, lightly-bittered historical central European wheat beer with a distinctive but restrained salt and coriander character. Very refreshing, with a dry finish, high carbonation, and bright flavours.
- Contains salt (0.5-2 g/L) not for salty flavour but for a balance of the acidity
- Coriander and orange peel are commonly used
- Lactobacillus-driven primary fermentation
- Saccharomyces added for attenuation and carbonation
- Acidity is the result of a secondary fermentation in open bottles
American Wild Ale:
The name American Wild Ale is commonly used by craft brewers and homebrewers. However, the word Wild does not imply that these beers are necessarily spontaneously fermented; rather, it indicates that they are influenced by microbes other than traditional brewer’s yeasts or perhaps that they are mixed-fermentation beers.
This category is intended for a wide range of beers that do not fit traditional European sour, wild, or spontaneously fermented styles. All of the styles in this category are Specialty-Type Beers, where many creative interpretations are possible, and the styles are defined only by using specific fermentation profiles and ingredients.
Controlling Acidity and Flavour Development
- Sour Beer Techniques:
- Turbid mashing creates wort with a portion of carbohydrates not fermentable by yeast but by other organisms for complex flavours.
- Kettle souring, a souring stage prior to a final boil containing hop additions, which allows lactic bacteria to produce lactic acid.
- Fermentation Temperature control:
- Higher temperatures (30-40°C) favour Lactobacillus growth.
- Lower temperatures (20-25°C) promote slower, more complex fermentation.
- Oxygen exposure:
- Limited oxygen exposure encourages lactic acid production.
- More oxygen can lead to acetic acid formation (desirable in some styles, but always very restrained).
- Time:
- Longer ageing allows for more complex flavour development. But if it is too long, the beer will get thin as all complex sugars are consumed.
- Brettanomyces can continue to work for months or years.
- Blending:
- Crucial for achieving consistency and balance.
- Allows for fine-tuning of acidity, flavour, and aroma.
Advanced Measuring and Evaluating Sour Beers
- pH meter: Essential for monitoring acidity levels, especially for kettle sours.
- Sensory analysis: Crucial for assessing flavour balance and complexity
- Titratable acidity (TA): Measures total acid content, a handy specification for commercial production.
By understanding these technical aspects, brewers can create a wide spectrum of sour beers, from refreshingly tart to complexly funky. Whether you're a homebrewer looking to experiment or simply a curious beer drinker, appreciating the science behind sour beers can enhance your enjoyment of these unique brews.
Remember, while the technical side is fascinating, sour beer production is as much an art as it is a science. The interplay of microbes, time, and environmental factors creates a truly alive and ever-evolving beer. So, grab a glass and savour the complex world of sour beers!
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