Science of Beer

Brewers must tap a wide range of biology and chemistry, from the pH of water to controlling yeast, to craft beer.

RALEIGH - Before tapping a keg and serving a glass of beer anywhere, a brewer must tap into a vast knowledge of chemistry and biology to craft his brew, and it’s all mixed with a pinch of the secret ingredient called experience.

“After all these years, you’d think I’d remember the thing about wearing glasses is you can’t see anything when the heat hits it,” says John Federal, production manager and brewer at Raleigh Brewing Company. Federal is holding the door to a huge, stainless steel tank open. Steam is pouring out. Federal pulls his head out and looks at a dial.

“Alright, that’s 100, and off we go,” he says, clapping his hands.

It’s 8am at Raleigh Brewing Company. There are roughly 500 gallons of a beer named Hidden Pipe Porter to be made. The company’s three brewers have been at work for a couple hours already, boiling water and sanitizing the tanks, piping and valves of the brewery’s production area. They are now ready to precisely choreograph a delicate dance of water, barley, hops and yeast to make their craft beer.

“You could say we are all a bunch of geeks and nerds because we have to know so much chemistry and science to do our jobs,” says Jamie McMillan, a brewer who is new to the company. “We do a lot of the chemistry ourselves because there is no other way to do it right."

The group has already added chemicals to the almost 450 gallons of tap water that will be needed. The pH balance of the water must be neutral to achieve the best brew. Normally, water from the City of Raleigh has more of a base chemistry, with a pH of 7.5.

The team first adds grain, in the form of malted barley and specialty grains, to the water. The mix is constantly stirred while it is cooked. The enzymes on the husk of the grain break down starches into fermentable sugars.

“Every step in the process is important,” says Federal, as he empties bags of grain in the top of the tank. Steam is billowing out. Inside, a giant arm stirs the mix. “We want to make sure the amount of grain we are adding to the mashton matches the amount of water we are adding so it's not too thick or too thin. You can have different activity from enzymes if you have it too thin or too thick.”

When the mix of grains and water reaches the proper temperature, the liquid, now called Wort, is drained from the wet grains, now called the Mash. The liquid is transferred to a new tank, mixed with hops for bitterness, and boiled. Hops are actually the flower of the hop plant. Beer brewers say adding hops while the tank is filling makes the beer have a more complex taste.

“Everything from the color to the carbonation level to the taste varies every time,” adds McMillan, who relishes in being able to take a break. The Wort and the newly added hops will boil for about an hour. “We get in a bunch of grain and it might have more sugars than the last batch, and we have to account for that. We get in a shipment of hops, which is needed for bittering the beer. And how much bittering you can get out of a hop is the alpha acid. That also varies.”

Until now, beer brewing has been all about chemistry. Now it turns to biology, as the mixture is pumped into a tank called the fermenter. Inside the tank, it is mixed with the single-celled organism yeast. Yeast is a fungus, a living creature that essentially lives off the ingredients in the beer. The yeast eats the sugar, leaving behind ethanol, which gives beer its kick, and carbon dioxide, which gives beer its fizziness.

Within minutes, a bucket sitting near the tank begins to bubble. There’s a hose running from the tank into the bucket. The bubbles are the carbon dioxide being produced by the yeast as it metabolizes the sugars. There is so much CO2 produced that the tank could possibly rupture from the pressure if the gas wasn’t vented.

Yeast is the most important ingredient in brewing, and the beer sits for five to seven days while the living yeast metabolizes all those sugars. Then the yeast is pulled out and the beer is kegged and ready to be served.

Ironically, while people guide the process, the yeast are the real chemists in the process. Yeast is the final component that determines the flavor of the beer and in fact, different types of yeast are used to brew different types of beer. So once the yeast is pulled out, brewers check it to make sure it is alive and viable. The yeast is used again in the next batch.

“Beer has been around a long time, but the actual science of brewing is relatively new in history,” says Dr. John Sheppard, a chemical engineer at NC State. Sheppard is advising North Carolina brewers on how to take care of their yeast. He’s also studying ways to regulate how yeast metabolizes sugars, which would help brewers to make more consistent batches of beer.

“Brewers didn’t know microorganisms were important for brewing until the mid 19th century,” adds Sheppard. “Because the yeast is really what turns the sugar into beer with all the flavors and qualities the consumer wants, I think it is key to control your yeast and make sure they are healthy and the right strain of yeast for your beer.”

The irony is, for all the shiny tanks and technology, the basic process that happened in the early morning hours at Raleigh Brewing Company is the same process that was practiced by the Sumerians of Mesopotamia (now southern Iraq). They are credited with the honor of inventing beer almost 10,000 years ago. 


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