: Fermentation completes, and the yeast clumps together (flocculates) and settles to the bottom, allowing the beer to clarify. Essential Brewing Resources
: Often called "top-fermenting" yeast because it rises to the surface during active fermentation. It thrives at warmer temperatures (typically 15–24°C / 60–75°F) and produces fruity esters and spicy phenols, which are characteristic of IPAs, stouts, and Belgian ales.
Brewing yeast acts as the biological engine of the fermentation process, transforming the sugary liquid known as into beer. This single-celled fungus consumes malt-derived sugars—primarily maltose and glucose—and converts them into ethanol (alcohol) and carbon dioxide (CO2) through a process called alcoholic fermentation. Brewing yeast and fermentation
The two most common species used in modern brewing are distinguished by their fermentation behavior and temperature preferences:
Fermentation typically unfolds in a consistent biological progression: : Fermentation completes, and the yeast clumps together
: The yeast acclimates to the wort, taking up essential nutrients like oxygen and amino acids to prepare for growth.
: As sugar levels decline, yeast activity slows. During this time, healthy yeast can "clean up" undesirable byproducts like diacetyl, which can otherwise cause off-flavors. Brewing yeast acts as the biological engine of
: Known as "bottom-fermenting" yeast, these strains settle at the bottom of the vessel. They ferment more slowly at cooler temperatures (typically 7–15°C / 45–59°F), resulting in the clean, crisp profiles associated with pilsners and traditional lagers. The Four Stages of Fermentation