The chemistry of beer and coffee

15 hours ago by Katherine Shonesy

University of Alabama at Birmingham professor Tracy Hamilton, Ph.D., is applying his chemistry expertise to two popular beverages: beer and coffee.

An associate professor in the UAB Department of Chemistry, Hamilton lectures for the American Chemical Society around the country about how the chemical makeup of these drinks impacts the characteristics of the products in final form.

"It's a really popular topic," Hamilton said. The scientists "love talking about beer and, of course, drinking it."

The theoretical chemist, who typically researches quantum mechanics, discovered a passion for zymurgy, the science of fermentation. His 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.

Even career chemists learn something in these lectures, Hamilton sayssuch 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; it is a product of the Maillard reaction, the same chemical reaction that browns steaks and bread crusts as they heat.

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. 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 said. "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 does not ferment long enough or correctly, it may taste like Granny Smith apples, thanks to acetaldehyde. This compound, produced as an intermediate step in fermentation, is not pleasant, Hamilton says. Another undesirable compound is 2-transnonenal, which tastes like damp paper.

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The chemistry of beer and coffee