How Things Work: Beer

Credit: Michael Setzer/SciTech Editor Credit: Michael Setzer/SciTech Editor

As evidenced by the outcry over the potential closing of the local bar Panther Hollow Inn last spring, Carnegie Mellon students love their beer. However, students here may not know how this refreshing drink is made and what gives it that smooth taste.

Beer is composed of four main ingredients: water, malt, hops, and yeast. The simplest explanation of the beer-making process is that the malt releases sugars into hot water, the yeast turns these sugars into alcohol, and the hops provide the bitter kick. But let’s go into more detail. What are the steps of brewing beer? In the book Beer Craft: A Simple Guide to Making Great Beer, William Bostwick and Jessi Rymill describe the process in six easy steps.

The first step is called mashing. This step is done the same way one might make a cup of tea, except instead of a small bag of tea leaves in a mug of hot water, a large mesh bag of grain (malt) is steeped in a stockpot of hot water. On John Palmer’s website “How To Brew,” he describes the malting process: “The debranching, beta-glucanase, and proteolytic enzymes do their work, preparing the starches for easy access and conversion to sugars.” Depending on the type of grain being used and what type of beer is being made, different grain-to-water ratios and different temperatures for the hot water are used. For example, Beer Advocate says that specialty dark malts are used in small quantities and produce stouts or bocks; roasted malts are used in mild and brown ales; and wheat malt, obviously, is a main component of wheat beers. The temperature of the water is dependent upon what temperature the enzymes in the particular malt being used perform the best at.

The second step is to sparge the wort — this is the sweet mixture left in the stockpot after the grains have been steeped for about an hour. In this step, the mesh bag of grain is removed, and the last of the wort drains into the stockpot. After the mesh bag has been drained, the grains must be rinsed in a fresh pot of hot water, then allowed to steep, and sparged again. This is to ensure the maximum wort is made from the grain.

The third step is boiling the wort. This is where the hops or other spices are added to the mixture. Some examples of hops that are listed on the website include Amarillo, Cascade, and Centennial, which are citrus-like spices used in India pale ales (IPAs), and the aromatic Hallertau and Liberty that are used in lagers and bocks. discusses the importance of timing during this step. Hops break down as they are boiled, causing their flavor to evaporate and disappear. Consequently, the more hops that are added early on during the boil, the more bitter the beer will be.

The fourth phase is chilling. This step is crucial because yeast cannot operate at the temperature of the boiled wort. During the chilling process, chunks of protein settle out of the mixture, leaving the beer nice and smooth.

When the wort is sufficiently chilled, the fifth step is funneling the wort into a fermenter, which is when brewers add the yeast to the brew and convert the sugars into alcohol and officially turn the mixture into beer. This occurs because the glucose enters in the yeast through diffusion and is broken down through glycolysis. This process results in pyruvates and adenosine triphosphate (ATP), according to

While the ATP is used to supply energy to the yeast, the pyruvates are converted by the yeast into carbon dioxide and ethanol — the alcohol. For the first day or two of fermentation, a blow-off tube should be attached to the opening of the fermenter to collect proteins, hop resins, and dead yeast cells. This tube is then replaced by an airtight cap, and the beer is left to ferment. This process takes approximately one week, although stronger beers require longer fermentation periods.

The sixth and final step is bottling. As in the case of transferring the wort from the pot to the fermenter, the transfer of beer from the fermenter to bottles must be done carefully with a tracking cane and tube to make sure no sediment gets into the bottles. After the bottles are filled and capped, they should be allowed to carbonate in a dark, cool spot for a week or two. The last test of patience comes after this, when the carbonated bottles must sit in the fridge for another week.

And with that, any student can ponder over the process and the science of brewing while enjoying a cold beer.