The Science of Winemaking

Chemical and Biomolecular Engineering (CBE) professors Talid Sinno and Bomyi Lim teach a mixed undergraduate-graduate course that applies principles students have learned previously — such as fluid mechanics and thermodynamics — to a real-world setting: wine production.

“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.

“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.” (Credit: Tobia Ruth)

Fermentation can happen in the presence of oxygen

Beccan Simon, fourth-year CBE major and engineering entrepreneurship minor from Wilmette, Illinois

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.”

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Top: Students in The Biochemical Engineering of Wine course visited Zorzal Wines in Mendoza, Argentina, which features views of the Andes. (Credit: Erica Sebastian)