Craft Beer Magic: Exploring Yeast's Impact On Flavor And Aroma

Yeast is one of the most important components of a beer recipe. Different strains of yeast have evolved over the history of brewing, adapting to their breweries and being selected for different characteristics by brewers. The strain of yeast you choose can profoundly affect the balance of the beer just by virtue of the mix of alcohols and esters that they produce. Every strain is different, but speaking in broad generalizations and bearing in mind that the flavors described may be subtle: Belgian yeasts emphasize spicy esters, English yeasts emphasize fruity esters, German yeasts tend to emphasize the malt, and American yeasts tend to have a clean character that emphasizes hop flavor.

Flocculation - some yeasts leave clearer beer

Flocculation is a process that occurs when yeast cells gather together and collect in a beer. High flocculation is often desired because it leaves a clearer beer. Some beer styles want a low flocculation yeast (e.g. Hefeweizen).

Yeast is one of the most important components of a beer recipe. Different strains of yeast have evolved over the history of brewing, adapting to their breweries and being selected for different characteristics by brewers. The strain of yeast you choose can profoundly affect the balance of the beer just by virtue of the mix of alcohols and esters that they produce.

Flocculation is often desired because it leaves a clearer beer. Some beer styles want a low flocculation yeast (e.g. Hefeweizen). Ale and lager yeasts are easily differentiated from each other physiologically by their ability to use the disaccharide melibiose (lager yeast does use this sugar, but ale yeast does not), growth at temperature above 37°C (98.6°F; lager does not and ale does), and the ability of the yeast culture to rise (ale) or drop (lager) in the fermenter.

Different yeast strains play an essential role in the creation of classic beer styles. Think of the clean, malt-forward character of lagers such as American Standard Lager, Czech Pale Lager and Bavarian lagers such as Helles, Dunkel, Bock, Festbier and Märzen.

Attenuation - amount of sugars consumed

Attenuation is the amount of available sugars that the yeast will consume. Different yeasts have different effects on beer, and attenuation is one of the factors that determine the final product.

Yeast is one of the most important components of a beer recipe, and the strain of yeast you choose can profoundly affect the balance of the beer. Different strains of yeast have evolved over the history of brewing, adapting to their breweries and being selected for different characteristics by brewers. The strain of yeast you choose can profoundly affect the balance of the beer just by virtue of the mix of alcohols and esters that they produce.

Some yeasts have high flocculation, which means that it collects or gathers together, leaving a clearer beer. However, some beer styles want a low flocculation yeast (e.g., Hefeweizen). Temperature range can also play a part in which yeast you use, as lager yeasts ferment at lower temperatures and ale yeasts at higher temperatures.

Alcohol tolerance is another factor to consider, as some yeasts don't stand up to the higher gravity beers such as Belgium tripples or Barleywines. Different yeast strains play an essential role in the creation of classic beer styles, such as American Standard Lager, Czech Pale Lager, and Bavarian lagers. Belgian yeasts emphasize "spicy" esters, English yeasts emphasize "fruity" esters, German yeasts tend to emphasize the malt, and American yeasts tend to have a "clean" character that emphasizes hop flavor.

Temperature range - yeasts ferment at different temps

Yeast is one of the most important components of a beer recipe. Different strains of yeast have evolved over the history of brewing, adapting to their breweries and being selected for different characteristics by brewers. The strain of yeast you choose can profoundly affect the balance of the beer just by virtue of the mix of alcohols and esters that they produce.

Temperature range can play a part in which yeast you use. General rule of thumb is that lager yeasts ferment at lower temperatures and ale yeasts at higher. Lager yeasts ferment at lower temperatures (below 37°C) and ale yeasts ferment at higher temperatures (above 37°C). Alcohol tolerance is another factor. Some yeasts don't stand up to the higher gravity beers such as Belgium tripples or Barleywines.

Different yeast strains play an essential role in the creation of classic beer styles. Think of the clean, malt-forward character of lagers such as American Standard Lager, Czech Pale Lager and Bavarian lagers such as Helles, Dunkel, Bock, Festbier and Märzen. Belgian yeasts emphasize "spicy" esters, English yeasts emphasize "fruity" esters, German yeasts tend to emphasize the malt and American yeasts tend to have a "clean" character that emphasizes hop flavor.

Among non-Saccharomyces wild yeast, those such as Pichia, Rhodotorula, Kluyveromyces, and Candida can negatively affect the quality of beer by causing haze or a film on the surface. Additionally, they may produce off-flavors such as diacetyl or phenolic compounds. Microscopic examination can sometimes provide clues to the presence of contaminated yeast because they are smaller and/or different shapes than typical brewer’s yeast. Otherwise, they can be detected using specific growth medium or genetic techniques.

Alcohol tolerance - some yeasts can't handle high gravity

Yeast is one of the most important components of a beer recipe. Different strains of yeast have evolved over the history of brewing, adapting to their breweries and being selected for different characteristics by brewers. The strain of yeast you choose can profoundly affect the balance of the beer just by virtue of the mix of alcohols and esters that they produce.

Alcohol tolerance is one of the factors that determine the type of yeast you should use. Some yeasts don't stand up to the higher gravity beers such as Belgium tripples or Barleywines.

Alcohol tolerance is a function of the temperature range in which the yeast thrives. General rule of thumb is that lager yeasts ferment at lower temperatures and ale yeasts at higher.

Alcohol tolerance is also a function of the amount of available sugars that the yeast will consume. In the proper environment, the cell absorbs sugar, oxygen and amino acids for cellular fuel.

Alcohol tolerance is also a function of the mix of alcohols and esters that they produce. Yeast, in turn, release ethanol, carbon dioxide and fruity esters as waste products.

Flavour profiles - yeasts produce different alcohols and esters

Yeast is one of the most important components of a beer recipe. Different strains of yeast have evolved over the history of brewing, adapting to their breweries and being selected for different characteristics by brewers. The strain of yeast you choose can profoundly affect the balance of the beer just by virtue of the mix of alcohols and esters that they produce. Every strain is different, but speaking in broad generalizations and bearing in mind that the flavours described may be subtle:

Belgian yeasts emphasize "spicy" esters.

English yeasts emphasize "fruity" esters.

German yeasts tend to emphasize the malt.

American yeasts tend to have a "clean" character that emphasizes hop flavor.

At times, beer yeast will also excrete organic acids, sulfur volatiles, spicy phenols, buttery diacetyl, fusel-type alcohols, and various other chemical components that may impact the aroma and flavor profile of the finished beer.

Some yeast has high flocculation, which means that it collects or gathers together. High flocculation is often desired because it leaves a clearer beer. However, some beer styles want a low flocculation yeast (IE Hefeweizen).

Different yeasts do different things when fermented in the same beer. Alcohol tolerance is one of the factors that can play a part in which yeast you use. Some yeasts don't stand up to the higher gravity beers such as Belgium tripples or Barleywines.

Frequently asked questions