Luke Pernotto

When I was younger every night at the dinner table each kid had to tell our parents what we learned in school that day. Looking back it was not something I particularly enjoyed, but now as a parent I understand that they were just reinforcing what we were learning in school. As I am going through a masters program for brewing science I can do the same here. It will give me another chance to refresh my memory on what I learned during the week and also maybe spark some interest in others.

The Lesson Learned this Week: Louis Pasteur was not the beginning and end of discovering yeast importance in brewing.

As long as I can remember reading and learning about beer, Louis Pasteur was always referenced as the individual who discovered yeast importance for fermentation. While it is true that his experiments in 1856 did prove that yeast were living organisms there were several others who played a role in the understanding yeast and fermentation. Pasteur’s discovery supported the idea of biogenesis or the idea that life comes from other life. While it seems obvious today, before his research yeast was thought to develop from the Spontaneous Generation Theory. This idea was that organisms can be created from inanimate matter.

Fermentation had always possessed a mystical quality. The Reinheitsgrebot (German Purity Laws) in 1516 did not include yeast as one of the allowed ingredients for brewing beer. Even though yeast was not known, brewing practices at the time actually facilitated the reuse of yeast. These practices like reusing the krausen from a successful batch and discarding from a poor batch. Fermentation yeast was also carried by brewing containers and/or brewing paddles. This reuse led to a domestication of brewers yeast. In 1680 Anton Van Leeuwenhoek first observed yeast cells. Unfortunately he ascertained that they were not living organisms. At the time and up until Pasteur’s discoveries yeast were thought to be chemical byproducts of fermentation. Similar to what we know CO2 and ethanol are today.

Even though the scientist Pasteur made the yeast discovery it was brewers who put this to a practical application. Emil Christian Hansen worked for the Carlsberg Laboratories in the Carlsberg Brewery. In 1883 he isolated the lager yeast (sacromyces pastorainus) from the mixed culture used at Carlsberg brewery. Hansen did this by diluting the suspensions of yeast he received from the production brewery. From this he grew new batches of yeast from sterilized wort. He continued to dilute the suspended yeast and ferment on sterilized wort until growth occurred in only a few of the vials. Through testing he was able to identify a single strain of yeast.

This isolation led to a development of a pure culture. This was different from earlier brewing where several yeast strains would be found in fermentation. He also established long-term storage of lager yeast techniques. This isolation and storage techniques facilitated the widespread adoption of lager style. This style of beer remains the most popular across the world.

How can I apply what I learned to the future: This seems like a good lesson to start on. The biggest thing I take away from this is the need for education and experimentation in brewing. Beer had been brewers for thousands of years without an understanding of yeast. It was only through research and curious minds that developments were made that led to the emergence of the most popular style of beer (lager) in the world and facilitated the stability of beer in storage for all beer. We would be just as foolish as the pre-historic brewers to think that there is not more to learn about beer.