Yeast – Are living organisms in the Fungi kingdom that convert sugar to alcohol during fermentation. There are many different strains of yeast that the brewer can use during the brewing process to make the desired style of beer. The primary categories of beer are ales, lagers, and lambics. Ales are known as top-fermenting or warm-fermenting because the yeast forms foam on the surface ferments between ~60 – 70 degrees F. Lagers are known as bottom-fermenting or cool-fermenting because the yeast tends to collect at the bottom of a fermenter ferments at a lower temperature around ~50 degrees F. Lager means to store in cool temperatures in German and does not pertain to fermentation. Lambics are known as spontaneous-fermenting or wild-fermenting because they are exposed to the wild yeast and bacteria and are brewed in Belgium. There are always exceptions with some beers that “blur” the lines on these descriptions, and craft brewers today can use strains of wild yeast for their particular beer. The taste of beer is also affected by the type of yeast used during fermentation.
Ale varieties include – Pale Ale, Brown Ale, Scotch Ale, Porter, Stout, Old Ale and Barley Wine, Belgian Trippel and Duppel, Wheat Beer, and others.
Lager varieties include – Lager, Pilzner, Bock, Dunkel, Helles, Oktoberfest / Marzen / Vienna, and others.
Lambic varieties include – Lambic, Gueuze, Mars, Faro, Kriek, and others.