ales lagers yeasts top-fermenting yeasts raffinose bottom-fermenting yeasts beers
Many beer styles are classified as one of two main types, ales and lagers, though certain styles may not be easily sorted into either category. Beers classified as ales are typically made with yeasts that ferment at warmer temperatures, usually between 15.5 and 24 °C (60 and 75 °F), and form a layer of foam on the surface of the fermenting beer, thus they are called top-fermenting yeasts. Lagers utilize yeasts that ferment at considerably lower temperatures, around 10 °C (50 °F), and have the ability to process raffinose, a complex sugar created during fermentation. These yeasts collect at the bottom of the fermenting beer and are therefore referred to as bottom-fermenting yeasts. Lagers constitute the majority of beers in production today.
