Fermentation feat: Extra special edition

Last year, four seniors drafted and set up a pilot fermentation lab. Led by Brian Pfleger, Karen and William Monfre Professor, Vilas Distinguished Achievement Professor, and R. Byron Bird Department Chair, and Josh Abraham (PhD’24) a PhD student at the time, they brewed some of the department’s first ever beer. But they also had a more important mission, to prep the lab space, set up equipment, and create experiments that ultimately amassed into a course manual that would be used for future courses. As students themselves, they provided a unique perspective on what skills are the most important for them to learn and which experiments they think students will enjoy the most.

Now their hard work has paid off and this spring the Department of Chemical and Biological Engineering offered an official fermentation course (CBE 562) to 12 exceptional seniors, with an “extra special” surprise!

The “extra special” challenge

The semester’s course was led by teaching faculty Brendan Blackwell with the help of graduate student Sarah Noga. But this time around, students received additional guidance on the brewing process from brewmaster Kirby Nelson at Lake Louie Brewing of Verona, Wisconsin—and a challenge. Their first project was to design a recipe for an extra special bitter beer that they would brew in the John C. Kuetemeyer Instructional Laboratories and afterwards a panel of brewmasters would evaluate the beers for their midterm. As a surprise, the winning recipe would be brewed at five-barrel scale at the Lake Louie brewery in Oconomowoc, Wisconsin.

For an extra special bitter—also known as an ESB—students had to follow the style profile which balances bitterness with the sweet malt flavor and has a pleasant, dry finish. While an ESB is an English-style Pale Ale, it’s distinct from an English-style Pale Ale with a fuller body and stronger composition. So the choice and ratio of ingredients, particularly the barley and the hops is very important. Acids in the hops, which can range in concentration from 2-20%, contribute to the bitterness so the choice of your hops as well as the amount determines the bitterness of the beer. Oils in hops also affect the aroma of the beer and need to be added late into the boil process or afterwards since they are highly volatile.

For brewing, the barley needs to go through a process called malting which involves soaking the barley in water to initiate germination and then drying it to halt the sprouting process. The malted barley provides the primary source of fermentable sugars for brewing, which are converted into alcohol by the yeast. Different barley malts have their own characteristics and can bring in unique flavors such as notes of toffee or caramel. It also significantly impacts the color of the beer as well. Other grains, such as wheat, spelt, rye and oats, can also be used though barley is by far the most popular.

Selecting the specialty malts and hops, which is where much of a beer’s varietal flavor comes from, lets each team of two personalize their brew and create unique flavor profiles within the range of a ESB. The six beers made by the class were: Bojuka Bog (by Nora Dixon and Summit Schultz), Bitter End (by Natalie Gatien and Kelsey Kemper), Bitter Critter (by Madison Herman and Griffin Smith), Fugacity (by Nathan Holland and Nolan Renick), Smooth Criminal (by Michael Maggiacomo and Jackson Puent), and B&B Bitter (by Benjamin Nagle and Binyang Wang). Each recipe had its own mix of 2-4 specialty malts and 2-5 hops in varying quantities. Collectively, the six teams used nine different types of specialty malts and six different types of hops, each team choosing their own interesting subset.

Battle of the beers

The panelists consisted of brewmaster Ryan Koga from Karben4 Brewing, head brewer Eric Brusewitz from Great Dane Brewing Company, and from Lake Louie Brewing Company brewmaster Kirby Nelson, bartender Carly Ross and president of the company Kevin Zerman. They mainly judged the six beers based on whether the beer adhered to the classic ESB style, which included color, taste, and aroma. The last factor they weighed was the finish of the beer, which for Nelson meant whether it was something he could imagine sitting down with on a warm summer day. Nelson thought the students did a very good job despite being “thrown to the wolves,” he said. “All the recipes were very nice interpretations and all had great hue to them,” Nelson commented.

In the end, Smooth Criminal won out in a close competition with Bitter Critter (2nd place) and Bojuka Bog (3rd place). Zerman described the winning recipe as if “a Spotted Cow and IPA had a love child and sprinkled some bitters in it. That’s what made [Smooth Criminal] number one.”

“This lab has been a lot of fun this semester, and I have really enjoyed having the opportunity to work on so many hands-on projects. I am very proud to have won the panel with Michael, and I’m excited to see where this class goes in future semesters,” said Jackson Puent.

Michael Maggiacomo had always been very interested in learning brewing. “Participating in the fermentation lab in the CBE curriculum was a surreal experience. I learned just how controlled the brewing process has to be, and just how much altering temperature and hops properties affects the taste and aroma of the final product,” said Maggiacomo.

Shortly after the winning brew was selected, students traveled to the brewery to help with the brewing process. They helped start the mashing process, adding the malt to hot water in a mash tun, which provides precise temperature control and stirring during the mashing process, creating a sweet liquid called wort. Once it’s done, they separated the liquid wort from the spent grains, moved it to a new tank for boiling and added the hops. They then left the rest of the brewing, fermentation and packaging in the hands of the brewmasters at Lake Louie.

We hope to continue collaborating with Lake Louie and see more student-developed beers enter the local market, so stay tuned next year!

Fermentation experimentation

Brewing combines many of the skills and lessons the students have been learning throughout their college career and the process itself is a complex interplay of chemical transformations. The breakdown of starches into fermentable sugars is a key stage, while the strategic timing of hop additions significantly impacts the beer’s profile. Early hop additions contribute the characteristic bitterness, whereas later additions impart desirable aromatic qualities. This highlights the sensitivity of hop chemistry to both heat and time during the boil.

Prior to full-scale brewing, students engaged in crucial experimentation, meticulously examining the impact of temperature variations on mashing and the effects of water chemistry, including pH and mineral content on the final product. The selection of an ESB for the first project was deliberate, chosen for its compatibility with the specific characteristics of Madison’s hard water.

“It was impressive how quickly the students got comfortable with the brewing process,” said Blackwell. “After one practice brew they confidently took ownership, wrote creative recipes, and produced some good beer!”

A valuable field trip to Lake Louie Brewing provided a crucial perspective on the distinctions between the students’ pilot-scale operations and industrial brewing. Processes that are relatively straightforward on a smaller 5-gallon scale—such as oxygenating wort for yeast health through simple agitation or achieving heat exchange with a coil—present significantly different engineering challenges when scaled up to large industrial tanks requiring sophisticated and consistent temperature control.

Other fermentation

While the students started the spring semester brewing, the class covered a broad range of fermentation processes including yeast, SCOBY, and lactose.

As a teaching assistant for the course, Sarah Noga worked closely with the students on their projects and experiments. “I really enjoyed seeing the students think on their feet about how to engineer solutions to accomplish the lab activities with the materials available,” said Noga. “This is something that can’t be taught in a classroom, so observing their creative problem solving was one of the best things about being a TA for this course.” 

Yeast

Used for brewing and other processes such as breadmaking, yeast is a single-celled fungus that breaks down sugars, like glucose, to produce energy, alcohol, and carbon dioxide. In breadmaking, there’s less total yeast fermentation, resulting in mostly carbon dioxide with a tiny amount of alcohol that typically evaporates during baking. Less fermentation occurs because of three reasons:

• The flour used in the yeast isn’t malted like grain used for brewing, so there’s less enzymatic activity.
• It involves lower temperature than the mashing process in brewing.
• There is less fermentable sugars and more starch remaining.

Furthermore, the mixing of flour and water results in long gluten proteins that form strong bonds to each other. These bonded proteins prefer a “coiled” state and stick together to form a dough. Kneading and stretching the dough encourages gluten formation. The gluten also helps capture more of the carbon dioxide that’s produced from the yeast in the mixture. So as time passes, the yeast ferments, producing carbon dioxide that’s then captured by the gluten in the dough, making the dough rise. Together, it’s your typical bread-making steps: mixing, kneading and rising.

In groups, students prepared samples of yeast with different water and sugar ratios, and mixed the dough for different lengths of time. Then, they covered and placed the samples either on the counter or in heated baths. Afterwards, they measured the height of the dough every 15 minutes for 90 minutes. At the end, they tested the strength of the dough by rolling it into a tube shape and holding it in the air from one end, letting it stretch and measuring the start and end length and radius. By doing this, students observed how the variables impacted yeast activity and gas capture, which determine dough texture and elasticity.

SCOBY

A symbiotic culture of bacteria and yeast, SCOBY is best known for its use in kombucha. SCOBY turns carbohydrates, like sugar, into acid which gives kombucha its tangy and fizzy taste. Because it’s composed of both bacteria and yeast, it’s highly variable and has a distinct chemical reaction comparatively. It also provided students a unique experience with fermentation that involves multiple organisms “collaborating” to survive together, which isn’t always the case. Students experimented with SCOBY fermentation by preparing four samples, a baseline sample, one with a higher sugar ratio, one starting with a lower pH (acidity), and another one with salt. They then tested the acid concentration of each sample over a few days and observed how long it took to complete fermentation.

Lactose Fermentation

Commonly known as lacto-fermentation, Lactose fermentation is a food preservation method where bacteria, primarily Lactobacillus, break down sugars to form lactic acid, creating a sour tangy flavor and extending a food’s shelf life. Lacto-fermentation is active in many common foods including yogurt, pickles, and a Midwest favorite, sauerkraut. Process like this where the fermentation acts not only adds flavor but extends a food’s shelf life, demonstrates to students the many functions and effects a process can have on a food’s chemistry and overall composition.

For lacto-fermentation, students experimented with different sugar concentrations in their samples. As the sugars turn into lactic acid and acidity increases, casein molecules stop repelling each other and start bonding. This “bonding” leads to the common effect of curdling. To see this effect, students tested the viscosity of the different samples over time while placing some in a warm water bath and some at room temperature. By draining the sample through a small hole in a cup over a few seconds and measuring the volume, they were able to get an approximate measurement for viscosity, which tells the students how quickly the fermentation is proceeding.

The final challenge

After experimenting with four fermentation processes, brewing, yeast, SCOBY, and lactose, one last challenge was issued to the students—to design and execute their own unique fermentation projects. The open-ended project is meant to foster innovation and provide a deeper understanding of the versatile biochemical process of fermentation. Armed with the lessons learned throughout the semester, students paired up and designed their own recipes. What helped most were their observations of the various experiments that tested how varying temperature, time, pH, and more can have on a product.

Factoring all variables and ingredients, students pursued their fermentation creations including sauerkraut, strawberry hard cider, plum wine, ginger beer, a second batch of beer, and Kvass—a Slavic fermented bread drink. After fermentation, professor Blackwell and Noga sampled all the creations and determined whether their recipe was successful, as in did it fit the flavor profile and expectation for their product.

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