Lactobacillus is a genus of bacteria found in natural environments like soil, plants, and the human body. These microorganisms are known for their ability to produce lactic acid through fermentation. In beer, Lactobacillus plays a dual role: sometimes an unwelcome contaminant, other times an intentional contributor. This versatility significantly shapes the characteristics and flavors of various beer styles.
Lactobacillus: The Uninvited Guest
Lactobacillus is a common spoilage microorganism in brewing, as it ferments sugars into lactic acid instead of alcohol. They can enter beer through inadequate sanitation, contaminated ingredients, or airborne exposure. Once present, they thrive in the beer’s low pH and anaerobic conditions, leading to undesirable changes.
Lactobacillus can cause several off-flavors and characteristics that diminish beer quality. They produce excessive sourness from lactic acid, leading to stale or yogurt-like tastes. Diacetyl, a buttery or popcorn-like aroma, also results from their metabolism of citrate. Beyond flavor alterations, Lactobacillus infection can lead to increased turbidity, making the beer hazy, and alter its viscosity, giving it a “ropy” or “silky” appearance.
Lactobacillus: The Creative Collaborator
Lactobacillus is intentionally employed by brewers to create distinct beer styles. These bacteria are crucial for traditional sour beers like Lambic, Gose, and Berliner Weisse, where lactic acid production is desired. Brewers cultivate specific strains of Lactobacillus to achieve controlled souring and unique flavor profiles.
Modern brewing techniques, like kettle souring, use Lactobacillus to produce tart beers. In this method, unhopped wort is inoculated with Lactobacillus strains, such as Lactobacillus plantarum or Lactobacillus brevis, and held at warm temperatures (38°C to 46°C) for 24 to 48 hours. This allows the bacteria to rapidly produce lactic acid before the wort is boiled to halt souring and kill the bacteria, ensuring stable acidity. This controlled acidification contributes a clean, tart flavor, distinguishing these intentional sour beers from those affected by spoilage.
Lactobacillus in Your Glass: Beyond the Buzz
A common question regarding beer containing Lactobacillus is whether it offers probiotic benefits. While many probiotic supplements contain various Lactobacillus strains, most commercially available beers, even sour ones, are unlikely to provide a probiotic effect. This is because the bacteria are often killed during pasteurization or out-competed by yeast and inhibited by hop compounds.
However, some experimental beers have been developed to include live probiotic strains. For example, researchers have created sour beers containing Lactobacillus paracasei L26, a strain with potential immune-regulating properties. These specialized beers aim to maintain a high count of live probiotics, typically at least 1 billion colony-forming units (CFU) per serving, to potentially deliver health benefits. Overall, Lactobacillus significantly impacts the final beer product, either by introducing unwanted off-flavors when present as a contaminant or by contributing desirable tartness and complexity when intentionally cultivated.