Animated gif of bubbling beer and steaming coffee

The Flavorful Science Behind Beer and Coffee

By Clair McLaffertyIllustration by Jessica Huffstutler

If you’ve never heard of zymurgy, you aren’t alone. But if you’ve ever tasted a beer, you’ve experienced it: Zymurgy is the science of fermentation. For Tracy Hamilton, Ph.D., associate professor in the Department of Chemistry, zymurgy is also a passion—and the topic of lectures he presents around the country for the American Chemical Society (ACS).

Hamilton initially became interested in brewing beer after he started teaching at UAB in 1991. At the time, some of the faculty were interested in fine wine, but beer presented a more affordable alternative. “I had just started appreciating drinks with lots of flavor,” Hamilton says. “Back then, the only way to get good beer was to make it.”

Later, Hamilton’s interest in flavorful drinks expanded to coffee when a member of his brew club began roasting beans. As with beer, Hamilton studied the chemical makeup of the beverage and began giving lectures on how coffee is cultivated, roasted, and brewed.

Avenues of Addiction

Despite the complexities of flavor in each beverage, their addictive properties come from predictable sources. For beer, it’s the alcohol content, while the caffeine in coffee is responsible for its allure. “Different people just have different responses to these compounds,” says Hamilton.

The theoretical chemist, who typically researches quantum mechanics, learned much of the information for his lectures by studying for the Beer Judge Entrance Examination. Afterward, he started giving talks around the Birmingham area and decided to become a speaker for ACS meetings. “It’s a really popular topic,” says Hamilton. The scientists “love talking about beer and, of course, drinking it.”

Even career chemists learn something in these lectures, Hamilton says—such as the fact that the flavor and aromatic compounds in beer and coffee are also present in other foods. Damascenone, for instance, which offers baked apple notes, is marketed as a flavoring agent (and is a product of the Maillard reaction, the same chemical reaction that browns steaks and bread crusts as they heat, Hamilton says.)

Flowers, Fruits, and Freshness

Flavors in beer come from a surprising number of sources. One is the variety of sugar-type compounds in the beverage, which give brews their sweetness, Hamilton explains. Other than the sugars, much of a particular brew’s complexity of tastes comes from the hops used in its production.

The essential oils in hops can “contribute a lot of flavors like citrus, grapefruit, and orange,” Hamilton says. “They’re what you smell.” Compounds such as geraniol and citral are extremely common in beer, giving it a geranium-like or citrusy smell, respectively.

Some flavor and aroma compounds can be less savory. If a beer doesn’t ferment long enough or correctly, it may taste like Granny Smith apples, thanks to acetaldehyde. This compound, produced as an intermediate step in fermentation, isn’t pleasant, Hamilton says. Another undesirable compound is 2-transnonenal, which tastes like damp paper.

However, some styles of beer don’t have much hop flavor at all and derive a lot of their flavors from the brewing yeast. “In ales, there are a lot of ester compounds that come across as pretty fruity,” Hamilton notes. “It’s all about the balance. You don’t want it to be overwhelming.”

In contrast, much of the flavor in coffee comes from pyrazines, he explains. These small aromatic compounds form much of the initial flavor of freshly brewed coffee. “That’s one reason coffee is so much better when it’s fresh,” says Hamilton. Other aspects of coffee’s flavor come from the sugars that are broken down by roasting.

Personally, Hamilton has been experimenting with traditional methods of brewing beverages. “I’m strictly a pot-and-physical-labor sort of brewer,” with no high-tech pumps or temperature-control equipment. Hamilton says. “I haven’t gone overboard in trying other things.” At the end of the day, the most desirable trait he looks for in a beer is that “every sip is the same,” he says. “Nothing lingering—that’s the most desirable outcome.”

Flavor Notes

• Refrigerating beer is the best way to optimize its flavor, Hamilton says. “The lower the alcohol content, the less time it will store well.”

• Storing whole-bean coffee in a freezer is O.K. if it’s in an airtight container with no condensation, Hamilton says. He usually doesn't freeze coffee himself, however. “I keep it in its green form, roast it when I need it, and use it within a week—grinding the beans right before brewing.”

Get Involved

• Learn about the undergraduate and graduate courses offered by the UAB Department of Chemistry.

• Give something and change everything for UAB chemistry students and faculty.