Lesson 5: Yeast and Life
Definition
Biologically, yeast is classified as a fungus - it is a living single-celled organism.
Forms
There are three forms of brewer's yeast: 1) dry, 2) liquid slurry and 3) slant. The dry form is similar to typical baker's yeast. Liquid slurry comes in two styles: yeast with starter and yeast without starter. A starter is a "mini-batch" of beer, and is used as feed for the yeast to increase the organism's cell count. A "slant" is a small test-tube-like vessel containing agar. An agar is a gelatinous material prepared from certain saltwater algae and used in bacterial culture media. In this case, yeast is the bacterial culture, and is grown on the agar and stored slanted in a test-tube-like vessel.
Types
Two types of brewing yeast exist. The first is ale yeast, or Saccharomyces cerevisiae. The second is lager yeast, or Saccharomyces uvarum. For a more thorough listing of the two types of brewing yeast, see Appendix A.
Usefulness
Unfortunately, dry yeasts are commonly contaminated with bacteria and/or wild yeasts. The slant form is something too rarely found. So, this leaves us using the liquid slurry form. In most cases we will go with the yeast without starter slurry and create the starter ourselves (mostly to save money).
In order to survive, ale yeast requires warm temperatures: 60-80F. In contrast, lager yeast requires cool temperatures: 35-50F.
A temperature above 80F will most likely kill yeast.
It is important to deliver ample oxygen to yeast during initial fermentation. In order provide this oxygen, we must agitate our wort (the combination of hops, malt, and water before the yeast is presented).
An adequate amount of yeast must be pitched or presented to the wort in order for yeast to survive. For our typical 5 gallon batches, this will be 500mL of yeast and starter.
Conclusion
Yeast is a living micro-organism that converts simple sugars into carbon dioxide, alcohol, and flavor. Yeast makes beer - the particular yeast chosen will determine what your beer will taste like just as much as any other ingredient you add.
Sources
Ray Daniels, Designing Great Beer, copyright 1996
Charlie Papazian, The New Joy of Homebrewing, copyright 1991
Charlie Papazian, The Home Brewer's Companion, copyright 1994
Stephen Snyder, The Brewmaster's Bible, copyright 1997
Appendix A: Ale and Lager Yeasts
Ale Yeasts
American Ale (Wyeast 1056)
Used commercially for several classic American ales. Dry, neutral-flavored. Finishes soft, smooth, clean, and well-balanced. A long secondary fermenation yields a dry, lager-like beer. Optimum fermentation temperature range: 60-72F.
American Ale (Yeast Lab A02)
This clean strain produces a very fruity aroma, with a soft and smooth flavor when fermented cool. All-purpose. Optimum fermentation temperature range: 65-66F.
American Ale II (Wyeast 1272)
Fruitier and clearer than 1056, slightly nutty, soft, clean, and slightly tart in the finish. Optimum fermentation temperature range: 60-72F.
Australian Ale (Yeast Lab A01)
All-purpose strain that produces a very complex, woody, and flavorful beer. Great for brown ales and porters. Optimum fermentation temperature range: 65-68F.
Bavarian Weizen (Yeast Lab W51)
This strain produces a classic German-style wheat beer, with moderately high, spicy, phenolic overtones reminiscent of cloves. Optimum fermentation temperature range: 66-70F.
Bavarian Wheat (Wyeast 3056)
Mildly phenolic and estery wheat beers. Optimum fermenation temperature range: 64-70F.
Belgian Abbey (Wyeast 1214)
Estery abbey-style for high alcohol brews. Optimum fermenation temperature range: 58-68F.
Belgian Abbey II (Wyeast 1762)
High alcohol tolerant yeast with a distinct warming character from ethanol production. Slightly fruity with a dry finish. Optimum fermenation temperature range: 65-75F.
Belgian Strong Ale (Wyeast 1388)
Robustly flavored yeast with moderate to high alcohol tolerance. Fruity nose and palate with a dry, tart finish. Optimum fermenation temperature range: 65-75F.
Belgian Trappist (Wyeast 3787)
A robust yeast with phenolic character. Alcohol tolerance to 12%. Ferments dry with a rich estery profile and a malty palate. Optimum fermenation temperature range: 64-78F.
Belgian Wheat (Yeast Lab W52)
Provides a soft, elegant finish with moderate esters and mild, spicy phenols. Optimum fermenation temperature range: 66-70F.
Belgian Wheat (Wyeast 3942)
Estery, low phenol-producing. Features an apple- and plum-like nose with a dry finish. Optimum fermenation temperature range: 64-74F.
Belgian White Beer (Wyeast 3944)
A tart, slightly phenolic character. High alcohol tolerance. Optimum fermenation temperature range: 60-75F.
British Ale (Wyeast 1098)
For the classic English pale or bitter ale. Slightly tart, diacetyl. Dry, crisp, fruity, and well balanced. Complex, but more neutral than Wyeast 1028-London. Optimum fermenation temperature range: 64-72F.
British Ale (Yeast Lab A04)
Excellent for pale ales and brown ales. Complex estery flavor. Ferments dry with a sharp finish. Optimum fermenation temperature range: 65-68F.
British Ale II (Wyeast 1335)
Decent clarity and malty flavor characteristics. Crisp finish, clean, fairly dry. Optimum fermenation temperature range: 63-75F.
Canadian Ale (Yeast Lab A07)
Very fruity when fermented cool. Good for light and cream ales. Optimum fermenation temperature range: 65-66F.
Dusseldorf Ale (Yeast Lab A06)
Full body, complex flavor, and spicy sweetness. Optimum fermenation temperature range: 65-68F.
English Ale (Yeast Lab A09)
Fairly neutral in character, producing a fruity, soft, and estery finish. A vigorous fermenter. Optimum fermenation temperature range: 64-66F.
European Ale (Wyeast 1338)
Complex, full-bodied, and sweet, finishing very malty. Produces a dense, rocky head during fermentation. Optimum fermenation temperature range: 60-72F.
German Ale (Wyeast 1007)
Ferments dry and crisp, leaving a mild and complex flavor. Produces an extremely rocky head; ferments well down to 55F. Optimum fermenation temperature range: 55-66F.
German Wheat (Wyeast 3333)
Features a subtle flavor profile for a wheat yeast with a sharp, tart cripness and a fruity, sherry-like palate. Optimum fermenation temperature range: 63-75F.
Irish Ale (Wyeast 1084)
Dry, complex, slight residual diacetyl and fruitiness, good for stouts and strong ales. Soft, smooth, clean, and full-bodied. Optimum fermenation temperature range: 62-72F.
Irish Ale (Yeast Lab A05)
Ideal for stous and porters. Slightly acidic, with a hint of butterscotch in the finish. Soft and full-bodied. Optimum fermenation temperature range: 65-66F.
Kölsch (Wyeast 2565)
A hybrid of ale and lager characteristics. This strain develops excellent maltiness and subdued fruitiness with a crisp finish. Ferments well at moderate temperatures. Optimum fermenation temperature range: 56-64F.
London Ale (Wyeast 1028)
Rich, minerally profile, bold and crisp - with some diacetyl production. Optimum fermenation temperature range: 60-72F.
London Ale (Yeast Lab A03)
A classic pale ale strain, very dry. A powdery yeast with a hint of diacetyl and a rich, minerally profile, crisp and clean. Optimum fermenation temperature range: 65-68F.
London Ale II (Wyeast 1318)
Great malt and hop profile. Fruity, very light with a soft, balanced palate. Finishes slightly sweet. Optimum fermenation temperature range: 64-74F.
Scottish Ale (Wyeast 1728)
Rich, smoky, peaty character ideally suited for Scottish-style ales, and smoked ales. Optimum fermenation temperature range: 55-70F.
Special London (Wyeast 1968)
Rich, malty character and balanced fruitiness. Optimum fermenation temperature range: 64-72F.
Swedish Ale (Wyeast 1742)
Stark beer with a floral nose and malty finish. Optimum fermenation temperature range: 69-73F.
Thames Valley (Wyeast 1275)
Produces classic British bitters. Features a rich, complex flavor profile and a clean, light malt character. Low fruitiness, low esters, well balanced. Optimum fermenation temperature range: 62-72F.
Trappist Ale (Yeast Lab A08)
Malty flavor with a balance of fruity, phenolic overtones when fermented warm. High alcohol tolerance. Optimum fermenation temperature range: 64-70F.
Weihenstephan Wheat (Wyeast 3068)
Unique and spicy weizen character, rich with clove, banana, and vanilla esters. Best results are achieved when fermentations are held around 68F. Optimum fermenation temperature range: 64-70F.
Lager Yeasts
Bavarian Lager (Wyeast 2206)
Rich, full-bodied, malty beers. Excellent for bocks and Vienna/Oktoberfest/Märzen. Optimum fermentation temperature range: 48-58F.
Bavarian Lager (Yeast Lab L32)
Use this classic strain for medium-bodied lagers and bocks, as well as Vienna and Märzen styles. Rich in flavor with a clean, malty sweetness. Optimum fermenation temperature range: 48-52F.
Bohemian Lager (Wyeast 2124)
Ferments clean and malty with a rich, residual maltiness. Optimum fermenation temperature range: 46-54F.
California Lager (Wyeast 2112)
Particularly suited for producing 19th century style West Coast beers. Retains lager characteristics up to 65F and produces malty, brilliantly clear beers. Optimum fermenation temperature range: 58-68F.
California Lager (Yeast Lab L35)
A California common beer strain. Malty with a sweet, woody flavor and a subtle fruitiness. Optimum fermenation temperature range: 64-66F.
Czech Pils (Wyeast 2278)
Perfect choice for pilsners and bock beers. Sulfur produced during fermentation dissipates with conditioning. Dry and malty finish. Optimum fermenation temperature range: 48-64F.
Danish Lager (Wyeast 2042)
Soft profile accentuating hop character. Rich, crisp, dry finish. Produces strong fermentation odors that soon fade. Optimum fermenation temperature range: 46-56F.
Munich Lager (Wyeast 2308)
Well-rounded, malty, smooth, full-bodied, and soft. Recommended for dunkels, bocks, and heavier German beers, but also makes a nice Vienna/Oktoberfest. Optimum fermenation temperature range: 48-56F.
Munich Lager (Yeast Lab L33)
Produces subtle and complex flavors, and a smooth and soft profile, with a hint of sulfur when fresh. Optimum fermenation temperature range: 50-52F.
North American Lager (Wyeast 2272)
Malty finish. Traditional culture of North American and Canadian lagers and light pilsners. Optimum fermenation temperature range: 48-56F.
Pilsen Lager (Wyeast 2007)
Produces a smooth malty palate. Ferments dry and crisp. For American pilsners and "steam" beers. Optimum fermenation temperature range: 48-56F.
Pilsner Lager (Yeast Lab L31)
Produces a lager that is light in both flavor and body, fermenting dry and clean. Optimum fermenation temperature range: 50-52F.
St. Louis Lager (Yeast Lab L34)
Produces a rounded, very crisp and clean, fruity flavor, with a medium body that is good for American-style lagers. Optimum fermenation temperature range: 50-52F.
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