Yeast Mode

I’m going to talk to you about the one worker at the brewery that never complains. It works for meals and a comfortable place to stay and happens to work for every brewery in the world. I’m talking about the unsung hero of the brewery. Without it we would not be able to make beer at all. I’m talking about yeast, or saccharomyces, meaning sugar fungus. I’m calling yeast a worker because it is alive and does a very specific and important job during the brewing process. Yeast is a single celled living organism that eats simple sugars and its byproducts are ethanol alcohol (the stuff that gets you drunk) and carbon dioxide (CO2). This job is called fermentation and without this process we would be unable to make any type of beer.

We have had an interesting relationship with yeast over our time on this planet. Almost since the beginning of human history we used yeast to make our favorite foods and drinks without even knowing it. The oldest discovered known writings turned out to be recipes for beer and bread in ancient Mesopotamia around 3100 BC. You would think if they are making beer 5000 years ago they had to know about yeast right? Actually no. Since yeast is a single celled organism it is very small and impossible to see with the naked eye. Yeast can be found in almost every climate and naturally floats around in the air.

For thousands of years we found that if we let sugar water (sweet wort) sit for a while after brewing, it would spontaneously ferment after getting infected with wild yeast just floating around. (This goes the same for bread dough before baking, which needs yeast to rise making the bread nice and fluffy.) This process was considered magic or a blessing from the gods. Only problem with relying on this method is not knowing about the most important ingredient. Every batch they made was a prayer to the gods. Many cultures even developed a god for beer and wine and a god of agriculture because of this unexplained phenomenon. Even without a full understanding of fermentation they still wanted to make consistent batches without relying solely on prayer. To do this they would note batches of beer or bread that actually tasted the way they wanted, then they would pitch a little of that batch into the next one. They found this to produce less bad tasting batches. (Many great sourdough breads are still made this way with a live culture kept and reused for every batch.) This was done for thousands of years until modern science brought us the microscope.

Yeast was not discovered until the invention of the microscope in the mid 1700’s by Antonie Van Leewenhoek. He didn’t know what yeast did or that it was even alive at the time. By the early 1800s yeast was widely thought to be the cause for fermentation but how or why it was happening was still considered a mystery. Then in 1857 Louis Pasteur (the inventor of pasteurization) was able to prove that yeast was alive and that it was causing fermentation by eating sugars and producing alcohol and CO2. Very quickly after Pasteur’s discovery we found that there are many different kinds of yeast. All of them had their own characteristics and would create their own flavors along with the alcohol and CO2. Scientists started isolating different strands to find there were thousands of different yeast strands but not all were suitable for brewing. All the yeast suitable for brewing can be separated into two main categories: lagers and ales. Ales are also called top-fermenting yeast because they will ferment at a warmer temperatures, 65-72 degrees Fahrenheit while lagers are called bottom fermenting and ferment at cooler temperatures around 45-55 degrees Fahrenheit. Ales also ferment faster than lagers taking around 2-6 days to ferment while lagers take 1-3 weeks to finish fermenting. Both ales and lagers can be found all over the world.

Like any living thing, different yeast likes to live in different regions of the world. Many regions in Europe pride themselves on their beer and the unique flavors that seem to only come from beer brewed in that region. It is all because of the yeast that likes to live in that region. Hence a Belgium style beer gets its unique flavor mainly from the yeast that is native to the Belgium region of the world.

Here at Iron Horse we use a basic ale yeast in all of our year round beers and many of our seasonals. Every yeast strain has its own unique flavors. Most of these flavors are pretty subtle but some can have big flavor notes that are really noticeable. The yeast will be responsible for 25-33% of the overall flavor of the beer. You may have noticed our year round beers have a very similar undertone to the overall flavor of the beer. This is because the same strain of yeast was used. So let’s raise a glass of glorious beer to yeast! Because without yeast there would be no beer to raise in the first place.

One comment on “Yeast ModeAdd Your Comment

  1. Conrad on

    These days the malt and hops used in beer are often posted for the beer geeks but the yeast you never know about so it’s fascinating. A brewer friend had the naturally occurring yeast in the hazelnut orchard where he lives identified and cultured for his farmhouse ales.


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