Malt, Hops, And Sours: What's The Deal?

Sour beers are those that have a notable tartness and a funky flavour. They are often fruity and sometimes vinous, with a complex depth of flavour. The sourness comes from the yeast, which gives off lactic acid. Hops are one of the basic ingredients of any beer, and they are used to impart a different flavour and aroma, or to add bitterness. They also have antimicrobial properties, which control bacteria levels. Hops are the spice of beer, providing bitterness to balance the sweetness of the malt. Malt, meanwhile, is the meat and potatoes of beer. It provides the sugars that are fermented by the yeast to create alcohol and CO2, and it is the primary source of beer colour.

Malted grains

Malting is one of the most fascinating yet least celebrated steps of the brewing process. It involves steeping either two-row or six-row barley in water for a couple of days. The barley is then aerated, turned regularly, and held at around 60°F to encourage germination. This process makes the grain more open to the fermentation process, where starches are converted into sugars that become alcohol. At this point, it is called "green malt".

The next step is to halt the germination process by drying the green malt with heat. Maltsters kiln, or dry, the green malt by slowly raising the temperature to more than 120°F. The final temperature depends on the desired type of malt. The growth of the sprouts is stopped, and what remains is a dried barley grain full of sugar, starch, and enzymes.

The level of heat applied to the green malt will determine the style of beer produced. Lower temperatures form the base for pale-colored beers like pale ales and lagers, while higher temperatures are used to make darker beers like brown ales, porters, and stouts.

Hops varieties

Hops are the spice of beer, providing bitterness to balance the sweetness of malt. They are cone-like flowers of a rapidly growing vine in the cannabis family. Hops impart flavours and aromas ranging from citrus and pine to earthy and spicy. The hops varieties used in brewing depend on the desired flavour profile and can be categorised into aroma hops, bitter hops, and dual-purpose hops.

Aroma hops have a lower alpha acid percentage and an oil profile that contributes to a pleasant aroma. They are typically used as finishing or conditioning hops. Examples of aroma hops include:

• Amarillo, with its flowery, citrus-like aroma and medium bittering value.
• Cascade, known for its grapefruit, pine, and spice notes.
• Citra, which adds citrus and tropical fruit characters to beer.
• Mosaic, a complex hop with notes of blueberry, tangerine, earth, and spice.

Bitter hops, on the other hand, have a higher alpha acid percentage and are primarily used during the boiling process to extract bitterness. Some examples of bitter hops are:

• Brewer's Gold, one of the earliest high-alpha hops, with a resiny and spicy aroma.
• Columbus, which is valued for its high bittering value and sharp, herbal character.
• Northern Brewer, a dual-purpose hop with woody, earthy, and fruity notes.

Dual-purpose hops possess the qualities of both aroma and bittering hops, contributing to both the flavour and bitterness of the beer. Some common dual-purpose hops include:

• Nugget, with a strong herbal and spicy aroma and high bittering value.
• Saaz, a classic noble hop used in European pilsners, known for its earthy and spicy character.
• Hallertau Mittelfrüh, the original German lager hop, which is grassy and easier to grow than other varieties.

Souring process

The souring process in beer-making involves introducing specific bacteria and yeast cultures to the wort, which convert the sugars in the wort into lactic acid, resulting in a tart or sour flavour. This can be done through traditional methods, such as barrel ageing, or faster methods like kettle souring.

Traditional Souring

Traditionally, sour beers were developed through a long, arduous ageing process, during which various bacterial and yeast cultures slowly turned the fermented beer sour. Brewers would create a beer through a conventional mash, standard boil, and primary fermentation. Upon completion of fermentation, the beers were transferred to barrels that harboured cultures of desirable microbiota. Over time, these microbes would produce the traditional sour flavours. This process could take up to two years.

Kettle Souring

Kettle souring is a faster method of souring beer, often taking just a few days. After creating the wort and conducting a brief boil for sanitation, the wort is cooled to a temperature range of 24-35°C (75-95°F). A pure culture or blend of Lactobacillus, the bacteria responsible for producing lactic acid, is then introduced. The Lactobacillus consumes the sugars in the wort and converts them into lactic acid, providing the desired tart flavour. This process typically takes 1-3 days.

Other Methods

In addition to the traditional and kettle souring methods, there are other techniques for souring beer, such as sour mashing and the addition of acids. Sour mashing involves using microbes on grain to create sourness but carries a high risk of contamination by unwanted bacteria. Alternatively, one can simply add lactic or phosphoric acid directly to the beer to increase its sourness.

Yeast

Sour beers undergo wild or mixed fermentation, where multiple yeast strains and bacteria work together to create the distinct sour taste. The primary yeast strain responsible for fermenting all clean beers, including sour beers, is Saccharomyces, also known as brewer's yeast. Brewer's yeast plays a crucial role in protecting the wort and initiating the fermentation process. It is a fast-working and highly IBU-tolerant yeast, making it an ideal base for sour beer production.

However, the yeast that is typically associated with sour beers is Brettanomyces, often referred to as "brett". Brettanomyces is a genus of wild yeast that ferments beer at a slower rate compared to Saccharomyces. This slower fermentation process can result in longer maturation times, with some brett-fermented beers taking months or even years to fully develop their unique characteristics. Brettanomyces produces a range of flavours, aromas, esters, and phenols, from fruity notes like pineapple to earthy tones reminiscent of hay or horse blankets.

In addition to Saccharomyces and Brettanomyces, other yeast strains may be used in sour beer production, such as Lactobacillus and Pediococcus. Lactobacillus, or "lacto," is a bacteria that converts sugars in the wort into lactic acid, resulting in a sour and clean-tasting beer. Pediococcus, or "pedio," is another lactic acid-producing bacteria that contributes to the sour profile of sour beers. Pedio takes longer to lower the pH of the beer, allowing the primary yeast strain to complete its fermentation before a significant drop in pH occurs.

The combination and proportions of these yeast strains and bacteria can be carefully selected by brewers to achieve the desired flavour profile for their sour beers. The fermentation process, whether controlled or open-air, also plays a role in the final product. By understanding and manipulating these variables, brewers can create complex and intriguing sour beers that offer a unique tasting experience.

Fermentation

The "big three" in sour beer fermentation are Brettanomyces, Lactobacillus, and Pediococcus. Brettanomyces (or Brett) is a wild yeast that is probably the most commonly used agent in sour beers. It is versatile, and depending on the strain, acidity, and alcohol levels and the presence of other microbiota, you can bring out a massive array of flavours that range from apple and pineapple to deeper pit fruits such as plum to earthy notes of horse blanket and hay. Lactobacillus and Pediococcus produce significant amounts of lactic acid (a nice, clean, sharp acidity), with Pedio taking substantially longer to do so than Lacto.

There are several methods for souring a beer, including traditional souring, quick souring, and "cheat" souring. Traditional souring involves creating a beer via a conventional mash, standard boil, and typical primary fermentation. The beer is then transferred into barrels that harbour healthy cultures of desirable microbiota, and over time, these bugs produce the traditional sours. Quick souring includes sour mashing and kettle souring, which are highly similar processes that give Lactobacillus a head start relative to the brewing yeast, creating a very pro-Lacto (and anti-everything-else) fermenting environment, and locking in the sourness in the beer first. "Cheat" souring involves adding acid directly to the beer.

Frequently asked questions