3 Different Ways Beer Ferments

The 3 main fermentation methods of beer are warm, cool, and spontaneous. 

1) Top Fermentation
also known as Top-Cropping or Warm Fermentation

The term “Top-Fermenting” is commonly associated with Ale Yeasts.

Ale Yeasts are regarded as top-fermenting yeasts since the yeast cells float to the surface during the fermentation process and then settles at the top of the liquid. Top-fermentation takes place at relatively warm temperatures of around 15 to 22 Celsius. The warm temperatures mean that the fermentation process takes a short amount of time, which ranges around 3 to 4 weeks.

Example of Top Fermentation Beer

• Ales
• Porter
• Stout
• Wheat Beer

2) Bottom Fermentation
also known as Bottom-Cropping or Cool Fermentation

The term “Bottom-Fermenting” is commonly associated with Lager Yeasts.

Lager yeasts are regarded as bottom-fermenting yeasts since the yeast cells gather at the bottom during the fermentation process.  Top-fermentation takes place at cold temperatures of around 4 to 10 Celsius. The slow chemical reactions associated with cold temperature mean that the fermentation process takes a longer amount of time, which ranges around 2 to 3 months.

Example of Bottom Fermentation Beer

• Lagers
• Pilsners
• Bocks

3) Spontaneous Fermentation “Wild Yeast”

This type of fermentation is a process that occurs when beer is exposed to open air to allow wild bacteria and yeasts to infect the beer. The combination of environmental factors (air, walls, wood, casks) where the beer is produced will determine its characteristics and taste. The end results are Beers that are often sour, tart, and non-filtered. This style of fermentation is different from the process of most mass-produced beer, where the fermentation takes place in a controlled environment.

Example of Spontaneous Fermentation Beer

• Lambic