One of the ingredients for brewing beer is yeast. This we all know. And we also know that the discoverer of this organism was Louis Pasteur, in 1860. But then, how is it possible then that beer was already produced thousands of years before?
The reason is simple: beer was produced the same as now, with yeast. What happened is that I don't know I knew that this bug existed. That is to say, the fermentation of the beer was carried out spontaneously thanks to the yeasts (and also the bacteria) present in the medium.
Yeast and the magic stick of the Vikings
There is a historical fact that you will surely love: one of the most precious possessions of the Viking families was the stick with which they stirred the beer's wort. Supernatural powers were attributed to it, since it was the tool that "made magic" and was passed from generation to generation.
What happened is that the yeast strains remained on that stick (which should not have been washed much), which when introduced into the must activated the entire process. On the other hand, there was also a kind of unconscious selection of the yeast by the brewers. These removed the foam that formed on the dough and added it to a subsequent batch of beer, thus carrying out the fermentation process.
When the existence of the microorganism was discovered, and above all, how it worked, it was passed to its controlled use. Thus, today, the final results of beer recipes can be predicted.
How does yeast work?
Within the exciting world of yeast, one cannot stop talking about the different phases in which it intervenes during fermentation:
- In the latency or adaptation phase, the yeast is added to the must and adapts to the environment.
- The yeast then absorbs oxygen to grow and reproduce.
- In the “fermentation” phase, yeast transforms most of the sugars into CO₂ , alcohol, and other by-products. The anaerobic phase begins.
types of yeast
In the world of beer there are three main types of yeast:
1. Ale or high fermentation yeast (Saccharomyces cerevisiae).
They prefer warm temperatures (between 13º and 25ºC) and are produced on the surface of fermenters.
Many of the historical styles are part of the Ale family, especially the English and Belgian, but also some German, such as Weisse.
These yeasts will produce fruity aromas, such as banana, pear, apple, apricot and peach.
2. Lager or bottom fermentation yeast (Saccharomyces pastorianus).
They develop at lower temperatures (between 5º and 12º C) and during fermentation process tend to settle to the bottom of the fermenters.
Many traditional German and Czech styles such as Pils, Bock, Marzen, Vienna, Schwarz, etc. but also some more modern with different geographic origin, such as American Lager or Indian Pale Lager.
Due to the fermentation temperature, a common feature in them is the lack of fruity notes, so the aroma will be given by the cereals and the hops used.
3. Wild yeasts or spontaneous fermentation (Brettanomyces).
Often the term "wild yeast" refers roughly to a generic category outside of classic top and bottom fermenting yeasts. That is, all those yeasts that are not Saccharomyces
The best known are the strains Brettanomyce s. Lambic, Gueuze, Kriek, Framboise are part of the family of spontaneously fermented beers.
Its aromatic profile will be characterized by spices and, occasionally, by lactic acids.
We hope you have learned a little more about the exciting world of beer! cheers!