The Science of Making Beer

08 November 2012
Published in Science and Society
Written by  Mike Horner

Approximately 12,000 years ago in the Middle East, the wonderful substance known as beer was first produced. People at the time enjoyed it, because it tasted great, made people feel good, and provided a disease-free source of water and nutrition.

The Sumerians even had a patron goddess of brewing. A poem written on clay tablets over 3,000 years ago praises her, and provides a recipe for beer.

Ninkasi, you are the one who bakes the bappir in the big oven
Puts in order the piles of hulled grains
You are the one who waters the malt set on the ground...
You are the one who holds with both hands the great sweet wort...
Ninkasi, you are the one who pours out the filtered beer of the collector vat
It is [like] the onrush of Tigris and Euphrates."

Today's typical recipe is not all that different. Barley, the foundation of beer, is encouraged to germinate for several days. Once an embryo has started to grow, the barley is dried and then toasted. This malting process breaks down grain starches into simpler sugars. Wort, a sugary liquid extracted from the malted grains, is then added to yeast, the driving force for fermentation.

From ancient Sumer to present day United States, the lure of beer is universal. Beer is the most popular alcoholic beverage in the U.S., with 6.3 billion gallons consumed in 2009. Utahns consume less than other states, ranking 45th in the nation, however, the craft brewing industry is thriving.

Wasatch Brewery was the first, starting in 1989, and 23 years later, there are at least 17 craft breweries in Utah. According to Greg Schirf, co-founder of Wasatch Brewery, between Squatters, Wasatch, and their consortium, they employ over 400 people.

Craft breweries are celebrated for experimenting with flavors. The different types of beer, from heavy dark stouts to light crisp pilsners, typically vary only by the proportions and varieties of four basic ingredients: water, barley, yeast, and hops.

Since beer is over 90% water, breweries take water quality and mineral content seriously, says David McKean, microbiologist at the Wasatch/Squatters Utah Brewers Cooperative, which makes beer for bottling and distribution. Often removing certain chemicals like chlorine and adding back others such as the mineral gypsum—calcium sulfate, which accentuates the hoppy flavor of beers like Indian Pale Ales. McKean says water is important for the final flavor of the beer "Everybody cares about the quality of their water," says McKean. "They are going to find what works for them with their starting materials, and what they want to end up with."

Grains, such as barley, are a key reason for the huge variety of beers. Darkly toasted barley imparts coffee, and chocolate flavors to rich stouts, while lightly toasted barley tastes more like bread or crackers and is used in German lagers. Stewing or smoking barley is a way to bring out complex flavors, such as toffee, caramel, or an almost bacon-like flavor.

The sugary stew, or wort, created by mixing barley and water is the starting point for beer. "We make the wort, yeast make the beer," says McKean. "They're going to be eating up the sugars. One glucose [sugar molecule] in, two ethanol, two carbon dioxide out."

Surprisingly, McKean says yeast can also be a source of flavor. He says different yeast produce divergent compounds such as isoamyl acetate ester, which tastes like banana or phenolic flavors that can taste spicy or like cloves. "You can take the same wort strain, feed it to a number of different yeast [varieties], allow them to ferment under essentially identical conditions and you will get wildly different [flavor] characters," says McKean.

A balancing component that counters the sweetness of beer and provides complexity is hops. Not added to beer until the 11th century, the flower clusters from the climbing plant contribute bitterness, flavor, aroma, and have antimicrobial properties that help preserve the beer. Now there are at least eighty hop varieties each with unique flavors ranging from pine and citrus to earthy and grassy, says McKean.

Many chemical compounds have been separated, purified, and identified within different hops varieties, says McKean. "You can look at some hops and say it's got this percentage of this and that." He adds that for many of the hop varieties, some of the main compounds are identical, so it is the combination of compounds that gives hops their unique flavors and aromas, "it's the interplay that has yet to be understood."

These four simple ingredients can be combined in limitless ways. But, ancient brewers knew nothing about yeast and fermentation. It wasn't until the 1800's when Louis Pasteur showed the single celled microorganisms convert sugar into alcohol, that the process was finally understood. Craft brewers today are using their knowledge of water, barley, yeast, and hops to manipulate these ingredients and develop a multitude of new flavors.

Kim Schuske contributed to this story.

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