What can result from contamination by wild yeast in brewing?

Contamination by wild yeast in brewing primarily leads to unexpected off-flavors, including sourness. Wild yeast strains, such as Brettanomyces, are often responsible for producing a range of flavor profiles that differ significantly from the clean, fermented flavors typically associated with standard brewing yeast like Saccharomyces. These wild yeasts can produce acids and other byproducts, resulting in a sour or funky character that many brewers seek in styles like sour ales or lambics, but which can be undesirable in other beer styles.

The presence of wild yeast disrupts the intended fermentation process and can lead to unpredictable outcomes, making it a common concern for brewers aiming for consistency in their products. While some brewers embrace wild yeast for specific beer styles, its contamination in conventional brewing can lead to flavors that are not intended and can be considered flaws in certain beer categories.