The general ingredients are water, hops, a grain and yeast. The grain is soaked in water to sprout, then heated and dried to stop germination and isolate its enzymes. This is malting. The malted grain is ground and steeped in hot water to activate enzymes that turn starches into sugar. This is mashing. The broth it creates is called wort, which gets drained and brought to a boil, then hops and other flavors are added. The wort cools, then yeast is added to consume the sugars and release carbon dioxide and alcohol. After this primary fermentation, ales are essentially done, but lagers and wild brews undergo a secondary fermentation and aging — “lagering” — some in tanks, some in barrels and others in bottles. How a brewer approaches each ingredient and step in the process determines the final product.
“Just by changing the temperature in the mash, you can adjust a beer’s profile,” says Gregory Deuhs, the master brewer for Peter Ballantine & Sons Brewing Co., a unit of the Pabst Brewing Co. in Milwaukee. Deuhs reverse-engineered the company’s iconic Ballantine India Pale Ale after the recipe was lost in a series of ownership changes. “At a lower temperature, you can get a lighter-style beer or at a higher one, you can get a full-bodied one,” he says. “[To re-create the Ballantine IPA] we did higher mash temperature, which resulted in more unfermentable sugars, and that gives the beer the full mouth feel and residual sweetness — which is what we want to balance off the hops.”
All beer, whether it’s some variety of pale ale, pilsner, porter, stout, kölsch or other, falls into one of two categories: ale or lager. Lager is derived from a word that means “to store,” and the style was discovered by brewers who stored beer in icy, cold caves during the summer for later use. The yeasts work at lower temperatures and tend to let malts and hops dominate. Ale yeasts work at higher temperatures and can result in a wider range of esters, the flavor compounds that can give beer a whiff of banana or some tropical fruit, like lychee.
Because it’s the main flavor driver, yeast is the core of the whole enterprise.
Different yeast strains tolerate or respond in varying ways to different levels of alcohol, and it’s these yeast strains that can create beers with vastly different flavors.
“We’re working with a live organism, so it’s unpredictable,” says Neva Parker, head of laboratory operations for San Diego-based White Labs, a 20-year-old yeast lab serving brewers and wine-makers with offices in four U.S. cities and Copenhagen, Denmark. “Change one thing, and it can completely change how the yeast is going to work. We can measure the level of flavor compounds using gas chromatography. We know how many each strain produces, but we don’t know why.”