UC Davis Coffee Researchers on the Science Behind a Perfect Cup of Coffee

UC Davis is known as one of the best schools to study winemaking. And now it’s becoming a magnet for faculty and students drawn to the study of coffee. What started as a popular undergraduate class has turned into a full-fledged research center – the first of its kind in the U.S. We talk to the director of the UC Davis Coffee Center and its head roaster about the science of coffee, including how to brew that perfect cup. What coffee questions do you have brewing?

Interview Highlights: 

Coffee is More Complicated Than Wine

Bill Ristenpart, a professor of chemical engineering and the founding director of the UC Davis Coffee Center, explains that coffee is even more complicated than wine. “It goes through more steps, more processing, both at origin and here in the United States where we roast it and brew it. And every single little step along the way affects the final quality of the coffee.”

Tim Styczynski, the head roaster at the center, adds: “The first thing they do is they let the seeds sit in a fermentation broth for one to two days. And that fermentation dramatically affects the flavor of the coffee. But to this day, the microbiology and the flavor chemistry is poorly understood.” Ristenpart notes the lack of academic investment in coffee compared to wine, despite coffee’s larger economic impact, as the motivation behind establishing the center.

Education and Research at the UC Davis Coffee Center

Ristenpart describes the center’s popular introductory course, where students learn scientific and engineering principles using coffee as a working example, culminating in a design contest to brew the best-tasting coffee using the least amount of energy.

Listeners express interest in attending workshops or certification programs offered by the center, with Styczynski mentioning plans for future public workshops. The experts discuss the center’s research into areas like the microbiology and flavor chemistry of coffee, as well as sustainability and agricultural economics.

The Journey to Appreciate Coffee’s Complexities

Both Ristenpart and Styczynski share their personal experiences that sparked their passion for coffee. Ristenpart recalls: “I ordered a cup of black coffee. And when I tasted it, I got a little upset because it had this, really profound, orange citrus note. And I’d never experienced anything like that in coffee before.” Styczynski reminisces about a cup of coffee he had 31 years ago, describing it as “chocolate and caramel and vanilla, but it had these incredibly beautiful citrus notes that were in perfect balance and…in harmony.”

Listeners also contribute their coffee journeys, with one caller, Tony, expressing gratitude for being able to appreciate the labor behind every cup after visiting a coffee farm in Guatemala, while another caller, John, praises the Aeropress system and pays tribute to Alfred Peet’s impact on bringing good coffee to America.

Factors Affecting Coffee Quality and Flavor

The interview delves into various factors that influence the quality and flavor of coffee, from cultivation and processing methods to brewing techniques and equipment. Ristenpart explains the significance of the fermentation process at origin, stating: “Most people here don’t realize that coffee is actually a fermented food product.” He also discusses the impact of water quality, with Tim noting how different water hardness can alter the acidity and sweetness of the same coffee.

When purchasing coffee beans, Ristenpart recommends buying whole beans rather than pre-ground, as grinding exposes the beans to oxygen, causing the delicate flavors to dissipate rapidly. He also advises checking the roast date, with some retailers removing coffee from shelves just 90 days after roasting. Investing in a quality grinder may be more worthwhile than an expensive coffee maker, as proper grind size significantly impacts extraction and flavor.

Brewing methods and equipment are also explored, with Ristenpart emphasizing the role of filter geometry and Darcy’s law in affecting the final brew. Listeners share their preferences for methods like Aeropress, French press, and pour-over, while the experts acknowledge the trade-offs between convenience and quality, particularly with single-serve options like K-cups.

Sustainability and Ethics in the Coffee Industry

The interview touches on the sustainability and ethical considerations surrounding coffee production, including the challenges faced by coffee farmers and the importance of initiatives like fair trade and shade-grown coffee. Caller Kristen highlights the importance of fair trade coffee to ensure growers are paid fairly, while another listener raises concerns about pesticide use and its impact on the environment.

Ristenpart acknowledges the complex economic issues involved, stating: “When you buy a cup of coffee that’s fair trade, some of the extra money might be going to the farmer or the person who owns the farm, but it might not necessarily be helping the people whose livelihood depends on, picking the coffee at that farm.” He also discusses the potential for more local coffee production in California as the climate changes, though notes the challenges of agriculture in the state compared to other regions.

This content was edited by the Forum production team but was generated with the help of AI.