The Science Behind Milwaukee’s Favorite Beverage: Beer!

Living in Milwaukee, it is easy to see beer is a part of our city’s culture and history. It plays a role in giving our city its distinct character and identity. What some Milwaukee beer lovers might not know is how strongly our beer history is tied to science and politics.

Milwaukee beer history goes back to the 1840s, when there was a large influx of German immigrants to the US due to political turmoil in Germany. Many of these immigrants settled in Wisconsin, especially Milwaukee, giving us a touch of German culture that has lasted through the centuries. The Germans brought their knowledge of beer with them, and breweries started opening across the state. Many of these breweries were only large enough to serve the neighborhood they resided in, and sometimes, neighborhoods formed around a new brewery. The breweries served as community centers, and hosted everything from weddings to town hall meetings. By 1856, there were over two dozen breweries in Milwaukee alone.

Newspaper clipping from 1936 from the Wisconsin Historical Society on the history of Schlitz Brewery, which opened in 1849 and was eventually acquired by Pabst in 1999. Image obtained from the Wisconsin Historical Society archives.

Most breweries served German style beers such as pilsners, since the brewmasters were German immigrants. However, during this time in the 1840s and 1850s neither the brewers in Germany nor Milwaukee truly understood the science behind the brewing process. Milwaukee draws its beer history from Germany, but the history of beer itself goes back over 7,000 years.

Early forms of beer were discovered in closed jars of grains that had started to ferment, or break down sugars to form alcohol. People started to realize that the grains fermented into alcoholic beverages if they were set out for the correct amount of time. The process was given the name “fermentation” based on the Latin word for boil, fervere, due to the bubbles formed during the process. While the process still  has the same name today, little was known about it back when it was named. People knew if the jars sat out for too long, the grains began to rot, and if it was not long enough, there was no alcohol content, but did not know why or how this happened.

Today, it is well understood that yeast is the microorganism that is responsible for this process. Yeast is a common bacterium used for bread, beer, and wine making that converts sugar to alcohol via fermentation while producing carbon dioxide (CO2) gas. However, it was not until the 17th century that yeast was even identified. It was first seen under a microscope, but was assumed to be starch molecules. No one knew its essential role in producing beer until 1755, when scientists learned that yeast was a necessity for wine, beer, and bread making. At this time, scientists knew yeast was necessary for fermentation, but assumed this was due to a chemical reaction rather than an organism living, growing, and metabolizing. It was not until 1835 that this discovery was made, and not until 1857 that the chemical reaction for fermentation was tied to the metabolism of yeast to produce ethyl alcohol and carbon dioxide.

Today’s brewers know a lot more about yeast, and take full advantage of that as shown in the yeast starter above. Photo by Paul Kern.

While early beer makers were successful without this knowledge, it certainly helps produce beer in the present day. The process is much more scientifically driven now, and while the underlying process remains the same, brewmasters are more acutely aware of the conditions of the fermentation process and preparation of ingredients. They have more control over their brewing thanks to science, and more control leads to improved consistency, less waste, and better beers.

Today, brewing begins by preparing the grains, which are usually malted barley, though can be oats, wheat, rye, corn or rice. The different grains give different flavors to beer. For example, wheat beers have a creamy texture while rye produces a more distinct and spicy flavor. The grains are the “food” for yeast, but must be prepared so the yeast can consume and process the sugars in the grains. This is similar to how meat must be cooked before it can be consumed and digested properly. Thus, the first step in beer making is to create a mash.

Some of the different grains that can be used for beer: barley, wheat, and corn.

In the mashing process, the grains or combination of grains are soaked in water. Just as the grains themselves are important to create a distinct flavor, the water quality is also important. Given beer only has four key ingredients, water, grains, hops, and yeast, each ingredient is extremely important, and water is no exception. Milwaukee brewers praise the fresh source of water from Lake Michigan. Minerals and impurities in the water can adversely affect the beer and yeast. Naturally occurring sulfur compounds are a common issue for brewers because they can add dramatic flavors to the beer, some of which are unwanted. Hydrogen sulfide (H2S) can be pleasant at low levels and is often found in pale lagers. It is a necessary compound for the yeast to grow and is volatile so it generally flashes off once the temperature is raised. However, at higher concentrations, H2S can produce an offensive rotten egg aroma that can ruin a batch of beer, and often does so when scaling up to produce larger batches. Sulfur dioxide can add a drying mouthfeel and is often used as a preservative in English beers. Dimethyl sulfide can produce flavors such as cooked corn or cabbage and often gives pilsners its fullness. Some brewmasters opt to use distilled, or purified, water and add in ions and minerals rather than using tap water to get better control of the end flavor. Once the brewmaster has determined the water quality and selected grains, the mashing process can begin.

In the mash, enzymes convert the complex and difficult to break down starches and proteins into simple sugars and amino acids that the yeast can easily take up and consume. Enzymes are macromolecules found in all living things and are a special type of protein that can accelerate reactions. Without the enzymes, this process would take much longer. Enzymes function differently at high and low temperatures, so the brewmaster has to be careful about this. At higher temperatures, the enzymes are less active and convert fewer sugars. Thus, there are more complex sugars that yeast cannot consume and are present in the final product, making a sweeter beer. At lower temperatures, there are more simple sugars that yeast can consume, leaving a more dry beer.

Soaking grains in the mash, and then boiling the mash and soaking hops for a home brew batch. Photos by Paul Kern.

The temperature is raised in order to stop the mashing process, and the mash liquid, or wort, is separated and boiled. Historically, this is to sterilize the beer, but now brewmasters know the temperature of the wort is also important for the end flavor of the beer. Hops are added to the wort to add a bitter flavor, and also act as a preservative. Without hops, the beer would be too sweet to drink. At higher temperatures, the hops release more bitter acids that cut the sugary sweet flavor of the wort. At lower temperatures, hops add flavor compounds instead. Timing is also an important factor, similarly to brewing tea. The longer the hops are soaked, more of the flavor transfers. However, if the hops are left to soak too long, the beer can become too bitter. Once the brewmaster is satisfied with the bitterness, the hops are filtered out and the wort is cooled. Now the yeast have everything they need to begin the crucial fermentation process.

While early beer makers used other plants and herbs to add bitterness to beer, hops became more popular because they function as a preservative (though the early beer makers were not aware of how or why). Today’s beer makers have more control over their hops and how it affects the end flavor.

The brewmaster selects an ale yeast or lager yeast to differentiate between the two styles of beers. Ale yeast ferments at the top of the tank and creates foam and bubbles as it consumes sugar. It also ferments at higher temperatures and is faster than lager yeast, resulting in more byproducts. Lager yeast sinks to the bottom of the tank and ferments at lower temperatures and is slower, producing fewer byproducts. Both the ale and lager yeast produce carbon dioxide and ethyl alcohol, as well as esters. Esters are a byproduct of the fermentation process and are a type of chemical compound that affect the flavor of the beer. Different esters create different flavors in the beer, the most common being ethyl acetate, which luckily is not very noticeable in beer because it smells like nail polish remover. Some of the more pleasant esters include isoamyl acetate which is popular with Belgian and wheat beers for its slight banana odor, or ethyl butyrate, which adds hints of passion fruit or pineapple. After the yeast has finished fermenting, the almost finished product is conditioned. Conditioning allows the yeast to absorb some of the “off” flavors that might have been produced due to byproducts such as the esters in the beer, or minerals such as calcium or sulfur compounds in the original water. The process takes approximately a week and the yeast settles to the bottom of the tank and is filtered out.

Ethyl acetate, (b) isoamyl acetate, and (c) ethyl butyrate, are some of the esters found in beers that give different flavors and aromas.

Now, the beer can be packaged to be sold in bottles, cans, or kegs. However, the science does not stop here. There are many steps a beer maker can take to adjust the carbonation or packaging process to affect the flavor, stability, and experience the consumer has with the beer. Much has changed from the 1800s when beer was manually poured into glass bottles for consumption.

Modern bottling plants are automated and can run over 60 bottles a minute!

Armed with the knowledge of the chemistry and biology that goes into beer, today’s beer makers experiment much more than the early Milwaukee beer makers. Different herbs and flavor enhancers such as basil or coffee are often added to create complex flavors. There are over 20 breweries in Milwaukee currently, and that number continues to grow. However, back in 1860, there were over 40 breweries in Milwaukee and over 200 in Wisconsin. The number of breweries took a sharp decline in the 1920s and 1930s due to Prohibition. Many small breweries had to shut down while others started making other carbonated beverages, malt syrup, or cheese in order to stay open. Milwaukee, true to its nature, resisted the prohibition. Residents feared negative side effects, such as a decrease in collaboration and camaraderie in the community, claiming that without alcohol, residents would be less social.

Newspaper clippings from 1919 (left) and 1932 (right) show the different viewpoints of Prohibition. Some supported the Prohibition while others denounced it for its negative social implications.  Images obtained from the Wisconsin Historical Society archives.

It turns out Milwaukee was right to be concerned, because there was an increase in crime and gangs, and a loss of jobs and community space. Wisconsin was the first state to repeal Prohibition in 1929. At the time, only 88 breweries remained across the state, nearly half of the number before Prohibition started. Senator John J. Blane, who initially proposed the repeal, then went on to propose an amendment to the constitution to repeal Prohibition across the U.S. Luckily, he succeeded. However, even with the repeal of Prohibition, the number of breweries in Wisconsin continued to decrease. By the 1970s, only 8 remained as the larger breweries such as Pabst, Blatz, and Miller started competing with the smaller, local breweries. Advances in technology for pasteurization, refrigeration, and transportation allowed these larger breweries to export beer outside of the neighborhood and state, leading to the decline of neighborhood breweries.

Presently, Milwaukee (and many parts of the U.S.) is seeing a rise in microbreweries that are taking the form of the original neighborhood meeting places from the 1800s. The breweries are bringing in new technologies, flavors, and experiences with their beers. Some breweries are even incorporating “green” practices, such as our local MKE Brewing, which uses solar power to heat up their water and wort, or Millercoors, which continuously reduces the amount of wastewater produced during manufacturing. It just goes to show that Milwaukee’s favorite beverage packs science and history (with a foamy top!) into one glass. Cheers!

Written by Palak Pujara for the Milwaukee Area Science Advocates (MASA)

Further Reading:

Alba-Lois, L. & Segal-Kischinevzky, C. (2010) Beer & Wine Makers. Nature Education 3(9):17

Damask, Kevin. (2017, Jan. 10). The Original Beer Boom: History of Brewing Runs Deep in Area. Star Times,

Brewing and Prohibition. Retrieved from


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