Which type of yeast is often referred to as 'top fermenting'?

The term 'top fermenting' specifically refers to ale yeast, which belongs to the Saccharomyces cerevisiae species. This type of yeast is characterized by its fermentation behavior, where the yeast cells tend to rise to the top during fermentation, especially during the active bubbling phase. This contrasts with bottom fermenting yeasts, like lager yeast, which sink to the bottom of the fermentation vessel.

Ale yeast operates effectively at warmer temperatures compared to lager yeast, typically fermenting between 60°F to 75°F (15°C to 24°C). This temperature range allows ale yeast to produce a range of flavors and aromas, including esters and phenols, contributing to the diverse profile of many ales.

The process of top fermentation allows for faster fermentation than that of bottom fermenting yeasts, leading to shorter brewing times for ales. This distinctive method directly influences the flavor profile and overall character of the beer, making ale yeast a crucial component in crafting various beer styles.