What is the difference between ale and lager yeast?
Brewers yeast is categorized into two main varieties. They are classified as ale yeast (top-fermenting type, Saccharomyces cerevisiae) or lager yeast (bottom-fermenting type, Saccharomyces uvarum). These two varieties are further broken down into categories of specific strains. There are hundreds of strains of both ale and lager yeasts. Ale yeast is a variety of yeast that is best used at temperatures ranging from 65-75 degrees F with certain ale strains performing well and indeed optimally as low as 55 degrees F. Lower temperatures tend to inhibit fermentation; some strains will not ferment below 50 degrees F. Some strains of ale yeast exhibit a tendency to flocculate at the surface of the fermenting beer during the first few days of fermentation, hence the term “top-fermenting.” Lager yeast is a variety of yeast that is best used at temperatures ranging from 45-55 degrees F with certain lager strains performing well at temperatures as low as 32 degrees F. The desired “smoothness” of
