The History and Function of Yeast in the Brewing of Beer


The Chemical Magic of Yeast in Brewing

louis-pasYeast has played a mysterious role in the brewing process since the early days of civilization; however, it wasn’t truly discovered until the late 1800s by Louis Pasteur. The fungus is responsible for producing a variety of compounds, including ethyl alcohol and carbon dioxide. Whether creating ale or lager in any form, yeast is a necessary component in the brewing process, and it’s worth exploring its history a bit further.

What is Yeast?

Everywhere you look, yeast is there. It is a spherical unicellular microscopic fungus that is so versatile and adaptable, you probably wouldn’t believe it existed if you weren’t so familiar with its byproducts.

While you wouldn’t be able to see it without a high powered microscope, yeast cells are egg-shaped micro-organisms that grow to a maximum size of six to eight thousandths of a millimeter. That’s not much bigger than a pinhead. Its tiny size means a 1cm cube weighs only one gram, yet contains more than 10 billion yeast cells.Microscope-Yeast

Yeast cells are made up of an outer layer of mannoprotein, an inner layer of glucanes, and a cytoplasmic membrane. The latter contains high protein complex content.

Yeast in the Brewing Process

In the absence of oxygen, yeast cells transform their sugars into carbon dioxide and alcohol. According to historians, this discovery happened accidently in Mesopotamia and Egypt where the first beers were brewed centuries ago. As various civilizations caught on to the amazing wonders of yeast and fermentation, each region began brewing its own local beer. Eventually, yeast became known as the “gift of god” – for many obvious reasons.

While the “gift of god” was enjoyed for many years, it wasn’t fully studied and researched until 1876 by Pasteur. It was at this point that specific brewing strains were selected and stored for optimization.

What was once a very rudimentary practice was perfected at the turn of the 20th most beers are spontaneously fermented with high or low fermentation yeast. Yeast ferments differently when stored at various temperatures and therefore produces multiple types of beer. For example, high fermentation yeast (15-20 degrees C) yields ales, while low fermentation yeasts (7-15 degrees C) usually produces lagers or pilsners.

The Value of Yeast

While brewing involves a number of calculated steps and careful attention to detail, many brewers claim yeast to be the most important ingredient in the process. Most won’t divulge details regarding the strains or temperatures they use, and brewers often consider their yeast “proprietary.”

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