The Biochemical Engineering of Wine course provides a real-world application of engineering principles, teaching students about the science behind the processes involved with making wine.
3 min. read
Students in The Biochemical Engineering of Wine course visited Zorzal Wines in Mendoza, Argentina, which features views of the Andes.
“Winemaking hits so many areas of chemical engineering that it really made sense to do this,” Sinno says about The Biochemical Engineering of Wine, a course he developed nearly a decade ago with CBE professor Scott Diamond.
This year it was listed as a Penn Global Seminar and included a travel component—undergraduates traveled to Mendoza, Argentina during Spring Break, coinciding with the country’s harvest season. Sinno says it was a chance for students to understand a single varietal wine—made from the malbec grape—and the impacts of elevation changes on the character of wine, as Mendoza sits at the foothills of the Andes.
A few students shared what they learned from the class about different aspects of winemaking.
(Left) The barrel aging room at Catena Zapata winery; (top right) an impromptu piano performance by classmate Junzhi Xie in the barrel room at Salentein winery; (bottom right) Vintage grape pressing equipment at the winemaking museum at Trapiche winery.
(Images: Kelly Williamson; (bottom right) Tobia Ruth)
How grapes are grown is important for the wines they produce
Khushi Singh, second-year master’s student in biotechnology from Albuquerque, New Mexico
Singh says that an important aspect of growing is the grape varietal: Drinking a riesling, chardonnay, and Gewürztraminer are all very different experiences of white wine, for example. But many other factors related to growing grapes have a profound impact on the final product.
“A grape grown in a cool climate is going to be more acidic and have less sugar,” she notes. This matters, she says, because these grapes will produce a lower alcohol wine than grapes grown in a warmer climate.
Other factors include rainfall during the growing period, sunlight, wine, soil moisture, and even how far apart the grapes are planted.
Fermentation can happen in the presence of oxygen
Beccan Simon, fourth-year CBE major and engineering entrepreneurship minor from Wilmette, Illinois
“In Mendoza, we had the opportunity to learn about the growing popularity of concrete eggs as wine fermentation and aging vessels,” says Colby Snyder, a fourth-year chemical and biomolecular engineering and physics major from from Reading, Pennsylvania. The eggs have a gentler effect on wine flavors than traditional oak barrels. “Their geometry—smooth surfaces without corners—facilitates convective currents, helping small particles remain in suspension without manual stirring.”
(Image: Tobia Ruth)
Simon says that his previous biology education generalized alcoholic fermentation as a process that is anaerobic, or without oxygen. But this course taught him that it is, in fact, more nuanced.
With high enough glucose concentrations, yeast can produce alcohol in aerobic conditions—the Crabtree effect, he explains. “This alcohol production can actually give the yeast a competitive advantage, as alcohol is toxic to many other microorganisms.” While this competitive advantage does not impact a winemaker’s strategy, he says, it’s relevant from the standpoint of fermentation science and how yeast works.
In Argentina, he was struck by the variation in fermentation processes across wineries. Traditional fermentation takes place in stainless steel tanks, and concrete eggs are growing in popularity, but Simon says that one winery added onto the traditional fermentation process with fermentation in unsealed small oak barrels. “A loose stopper on the barrel was sufficient to prevent harmful oxidation,” Simon says, “as carbon dioxide produced in the fermentation reaction acts as a gas barrier.”
Different pressing techniques are used for different wines
Magdalena Miller, fourth-year CBE major from Easton, Maryland
The most common white wines, such as chardonnay and sauvignon blanc, are made from green grapes. But this course taught Miller that white wine is sometimes made by pressing red grapes and removing the skin before fermentation. For example, winemakers can use Sangiovese and tempranillo grapes to make white wine by minimizing skin contact.
“In white wine manufacturing, color and tannins from the skins and seeds are undesirable, so pressing uses a high surface area to gently release all juice without extracting any compounds,” she explains.
Miller says that early methods of pressing used baskets, but modern technology includes the use of pneumatic and continuous screw presses. She found this course an interesting comparison to her internship last summer at Ocean Spray, where instead of pressing, cranberries are first frozen and thawed to break down cell structure.
(Left) At Piedra Negra winery, a student blends a custom wine for a friendly competition, with winemakers at the winery judging the resulting wines. (Right) A staff member at SuperUco winery explains how vineyards in different locations across the Mendoza region lead to very different malbec wines.
When and how these processes are carried out affects taste and smell
Nick Aiello, first-year CBE Ph.D. student from Freehold, New Jersey
One thing Aiello learned is that red wine elicits a dry mouthfeel because the grapes are subjected to extended contact with grape skin during fermentation, which yields more tannins. Another is that excess exposure to light can degrade riboflavin (vitamin B2) in wine, leading to a rotten egg or burnt rubber smell in bad wines.
He says that while previous classes touched on compounds like esters, which are responsible for giving foods like bananas their taste and smell, this class showed him that concentrations can be very low and still have a meaningful impact on smell.
“As a result, wine producers have to be very intentional about their process, which reinforces much of what I’ve learned about chemical engineering—that everything is done with a purpose,” he says. “I have no doubts that I’ll continue to think like this as I continue my graduate research.”
Students listened to an information session in a vineyard at Cobos winery prior to a sit-down tasting.
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