The Science of Beer

They may have been Puritans, but beer was their choice of beverage to bring on a voyage to America.

Beer was safer than water because it had been boiled, not for safety, but to bring out bitterness, flavor and aroma. It’s one of a chain of processes that convert raw ingredients into the world’s most widely-consumed alcoholic beverage.

It turns out that beer requires a surprising amount of science.

Former Duke grad student Dr. Tim Wadkins, a brewer and winemaker, spoke about this science in a May 17 talk sponsored by the Department of Molecular Genetics and Microbiology, the Department of Cell Biology and the Center for the Study of Aging and Human Development.

“Brewers like to tell you that they make beer,” Wadkins said. “But they’re really making food for yeast to make beer.”

Wadkins described four ingredients that every brewer needs. Germinating cereal grains, also known as malt, produce enzymes that convert starches into sugars. Heating prevents the grains from germinating further.

Hops are the female flower clusters of the hop plant (Humulus lupulus). They act as a natural preservative and add bitterness, flavor and aroma to a beer when boiled. “They’re all flowers,” Wadkins said. “Some can be as different from one another as the smell of a rose from the smell of a tulip.”

Yeast are living microscopic organisms that munch sugar from the malt to create carbon dioxide (“fizziness”) and ethyl alcohol (“dizziness”). The type of yeast dictates many components of a beer’s taste. So-called “wild” yeasts can yield flavors as variant as pineapple, butterscotch, bacon and Band-Aids. Some flavors are produced deliberately, but others (eau de Band-Aid?) emerge as an unintended byproduct of the process, perhaps because the beer is too old or wasn’t packaged properly.

Water is easily overlooked, but critical to the beer-making process. “If your water doesn’t taste good at your brewery, then your beer is never going to taste good, no matter what you do to it,” Wadkins said.

After thorough malting, milling, mashing, lautering, boiling and fermenting, the beer is ready to go. But there’s one last thing. Isohumulone compounds contribute to beer’s bitter taste, but they also react with light to produce MBT, a compound you may recognize if you’ve ever gotten on a skunk’s bad side. Fortunately for us, brewers usually package their beer in cans or very dark bottles to prevent this process from occurring.

Provided by Duke University