What role does play yeast in breweries?

In breweries, yeast plays a crucial role in the fermentation process, converting the fermentable sugars present in the wort (unfermented beer) into alcohol and carbon dioxide. The specific type of yeast used in brewing, known as brewer's yeast or Saccharomyces cerevisiae, is a strain of fungus that has been domesticated and cultivated for its fermentation capabilities.

Here's an overview of the role of yeast in breweries:

1. Fermentation: The primary function of yeast in brewing is to carry out fermentation. During fermentation, yeast cells consume the fermentable sugars, primarily maltose, glucose, and sucrose, present in the wort. Through the process of glycolysis and subsequent metabolic pathways, yeast converts these sugars into ethanol (alcohol) and carbon dioxide (CO2).

2. Alcohol Production: The alcohol content of beer is directly influenced by the yeast's fermentation activity. The yeast's ability to metabolize sugars and produce ethanol determines the final alcohol by volume (ABV) of the beer. Breweries carefully select yeast strains based on their fermentation characteristics and the desired alcohol levels in their beers.

3. Carbonation: The carbon dioxide produced by yeast during fermentation is responsible for the carbonation in beer. The CO2 becomes trapped in the liquid, resulting in the bubbles and effervescence that are characteristic of beer.

4. Flavor and Aroma: Yeast also contributes to the flavor and aroma profiles of beer. Different yeast strains possess unique properties and can produce various flavor compounds and esters. These compounds influence the sensory characteristics of beer, such as fruity notes, spicy aromas, or subtle sweetness.

5. Attenuation: Attenuation refers to the degree to which yeast ferments the available sugars in the wort. Different yeast strains have different attenuation rates, which impact the residual sweetness or dryness of the final beer.

6. Flocculation and Sedimentation: After fermentation, yeast cells typically flocculate, clumping together and settling at the bottom of the fermentation vessel. This process aids in the clarification of the beer and helps remove yeast from the finished product.

7. Byproduct Formation: Yeast metabolism during fermentation also produces various byproducts, including higher alcohols, organic acids, and esters. These compounds can contribute to the complexity of beer flavor and aroma.

Overall, yeast is essential to the brewing process, as it transforms the sweet wort into the alcoholic and carbonated beverage we know as beer. The art and science of brewing involve carefully managing yeast strains and fermentation conditions to achieve the desired beer styles, flavors, and aromas.