By Nick Houtman
The next time you sip a beer with friends, consider the source: barley prompted to sprout, only to have its development arrested; yeast that turns barley sugars into alcohol and carbon dioxide; hops bred to produce fragrant oils for flavor and aroma. These are the tools of the brewer’s art, which turns grain, microbes and flowers into a liquid feast.
Oregon State University assists the brewing industry by developing new varieties of barley and hops. And like chefs in a gourmet kitchen, students and faculty in OSU’s fermentation science program — key to the new $18 million Oregon Quality Food and Beverage Center being built on the Corvallis campus — collaborate with craft beer-makers on new recipes for this ancient drink.
Like all fermented foods, beer is the result of a finely tuned living process. It reflects the same biochemical principles that lead a seed to become a plant, make bread rise and enable us to savor and digest a meal.
While there are endless variations to the brewer’s art, here are the simplified steps, courtesy of Tom Shellhammer, the Nor’Wester Professor of Fermentation Science in the College of Agricultural Sciences and an internationally recognized expert in hop chemistry.
Origins: Making Malt
1. Barley soaked in water begins to germinate.
2. In the awakening seed, a hormone (gibberellin) triggers the development of enzymes within the barley that turn complex starches and proteins into nutrition — simple sugars and amino acids — for the growing embryo.
3. But before the new shoot can emerge, the maltster dries the wet grain to stop this enzymatic action and preserve it for the brewer.
4. For pale beers, the malt is lightly kilned. For darker brews, such as porters and stouts, the malt is kilned hotter and longer to develop more color and flavor.
In the Brewery — Mashing and Boiling
5. The brewer grinds the malt into a coarse grist and combines it with warm water to create a thin soup, aka mash. Sugars produced during mashing can be fermented by yeast while the remaining starches cannot. 7:3 is the average ratio of what’s fermentable to what’s non-fermentable in wort. Fermentable sugars will ultimately yield alcohol, while the non-fermentables will affect the beer’s flavor, mouthfeel and satiating quality.
6. The enzymes created during malting begin breaking down the malted barley’s starch to produce a rich broth containing sugars, amino acids and an array of compounds that provide flavor and aroma.
7. Separated from the spent grains, which are often sold off as animal feed, this liquid called wort is the foundation for the final product.
8. The brewer boils the wort to sterilize it and to extract essential oils and acids from hops, which are added as the liquid cooks. The female flower of the hop plant, Humulus lupulus, includes lupulin glands. Found deep inside the hop cone, these glands contain the oils that deliver herbal, floral, citrus and tropical aromas and acids that can pack a bitter punch in the finished beer. Boiling hops in wort produces iso-alpha acids which contribute bitterness and antimicrobial properties to beer. Brewers sometimes add hops after boiling or during fermentation in an effort to turn up the hoppy aroma while minimizing their bitter contribution in the final product.
Yeast in Time
9. Enter a single-celled microbe, Saccharomyces cerevisiae, the workhorse of alcoholic fermentation. With the wort cleared of all microorganisms by sterilization, yeast provides the last critical transformation, turning simple starches and sugars into ethanol at a ratio of two units of sugar to one of ethanol.
10. Yeast also produces a host of other compounds (organic acids, esters and alcohols) that lend winey, fruity and other flavors to beer. Brewers reuse their yeast from previous fermentations in a process that can take two to 10 days. Choosing one of the thousands of yeast strains is part of the art.
Editor’s note: For a thorough review of OSU’s beer-making research from barley to hops, see the fall 2017 issue of Oregon’s Agricultural Progress magazine