The science of beer, from the barley to your belly

By Colleen Seidel

I’ve always been more comfortable typing away in front of a computer screen than sitting behind… I’ve always been more comfortable typing away in front of a computer screen than sitting behind a lab bench mixing chemicals and staining cultures. I’ll be honest: As a college student, my body of scientific knowledge doesn’t extend far beyond that which I learned from Bill Nye’ ‘mdash; in the fourth grade. But, little did I know, there’s a veritable science lesson in every glass of Yuengling or Sam Adams or Dogfish Head that I happily consume every weekend. I stumbled upon last week’s edition of NPR’s ‘Talk of the Nation: Science Fridays,’ in which Gavin Sherlock, a genetics scientist at Stanford University’s School of Medicine, explained his research in genetically coding different strands of lager yeast, and it piqued my curiosity. Just what is so scientific about beer? And why were we never taught this in freshmen biology? After perusing the Internet on sites like and a rather informative student page from Rensselaer Polytechnic Institute (Google something like ‘science of beer’ and you’ll find both pages and tons more), it turns out that the process of brewing a pint or two is actually quite scientific. It all starts with the four basic ingredients of beer: barley, hops, yeast and water. The brewing process employs the seeds of the barley plant, but unlike the beef barley soup my mom used to make, you can’t just throw the seeds into a pot and start to brew. Instead, the seeds have to germinate first ‘mdash; that is, they have to start sprouting. This sprouting occurs by flushing the seeds with water, then draining them and holding them at a constant temperature of 60’deg;F for five days until sprouts show. These germinated barley seeds are then dried in kilns at temperatures up to either 122’deg;F for lighter malts or 220’deg;F for darker ones. The germination process of the barley seeds is crucial to beer brewing. By germinating, the seeds produce the enzymes necessary to break down starch (long chains of sugars) into simple sugars (short chains) in a process that produces a sweet, sticky liquid called ‘mash.” These short chains of sugars can then be fermented by yeast later in the brewing process. Hops are those things in beer commercials that the burly-looking brewers are always running their hands through, holding up to their faces and smelling.’ That explains almost nothing about what hops actually are and their role in the process of brewing beer, though. Hops are actually the flower of the hop vine ‘mdash; interestingly enough a member of the hemp family ‘mdash; and their role in beer is to provide flavor and aroma from their highly water-soluble oils and bitterness through their resins, named Alpha and Beta acids. It is in the boiling step of the brewing process, the step that comes after the mash, that hops are added at different intervals depending on their purpose. The first hops added to the boil contribute the bitterness tothe beer. Because these bitter acids of the hops are not easy to extract, the hops have to be boiled for 90 minutes.’ Near the end of the boiling stage, the ‘finishing hops’ are added, which contribute the flavor and aroma of the beer. Since these flavoring oils are relatively easy to extract and can evaporate quickly, the finishing hops only have to be in the boil for a few minutes. Next comes yeast, which makes all the magic happen. In fermentation, this tiny single-celled organism is responsible for converting those simple sugars into the alcohol and carbon dioxide (i.e. gas) we all know and love in our beer. It does this by a process called glycolysis that breaks glucose molecules down into carbon dioxide and ethanol (alcohol) molecules through chemical reactions. Interestingly, the type of yeast used in fermentation helps to determine the type of beer that is brewed.’ In this sense, there are two main types of yeast. ‘Ale yeast,’ or ‘top-fermenting yeast,’ named such because it initially collects at the surface of the beer, is used to make ales and stouts in a temperature range of 55-75’deg;F. ‘Bottom-fermenting yeast,’ better known as ‘lager yeast,’ is used to make lagers. Lager yeast takes substantially longer to ferment sugars, and it works best at a much cooler temperature range of 32-55’deg;F. Having satisfied my intellectual query into the science behind beer, of which there is far more technical and explanatory information out there than what I described here, I decided it was still best to leave the science stuff to the experts and just stick with what I know’mdash; that is, consuming it, which, I think we can all agree, involves a lot less thinking and a lot more fun.’ I would like to advocate the idea that we bring Bill Nye back to television with a show geared towards college kids. Just a thought.