How brewers turn barley into beer, in four (very geeky) steps

With new craft breweries opening in Los Angeles seemingly every month, there’s never been a better time to take a visit, get a fresh pint, and see how the beer is made.

The basics are pretty much the same. Whether it’s a refreshing Pilsner, a pungent IPA, or an inky stout that’s brewing, here’s an explanation of some of the basic equipment that brewers use to coax all that flavor from just a handful of simple ingredients. It might seem like magic, but it’s really just a lot of science and tightly controlled processes that turn malt, hops, water and yeast into ales and lagers.

There are, of course, many variations in equipment and technique, and many finer details are glossed over. But this gives you the basics to understand what all that shiny stainless steel you see on a brewery tour is actually for.

Mash tun

The first major vessel in the journey from grain to glass is the mash tun, where the milled grains are combined with hot water (called “hot liquor” by brewers) and left to steep at a particular temperature (usually between 145 and 155 degrees Fahrenheit).

In about an hour, enzymes in the crushed barley kernels convert some of the starch in the grain to sugars. The temperature determines how much of the sugar will be the fermentable simple sugars that yeast prefer, and how much will remain unfermented (adding residual sweetness and body to the final brew). As the starch conversions near completion, the brewers raise the temperature of the porridge to stop the enzymatic reactions. This “mash out” is followed by “laundering” — draining the sugar-laden liquid (known now as “wort”) from the mass of spent grain husks and pumping it to the next vessel in the process, the brewing kettle.

Kettle

The wort is boiled in the kettle, usually for about an hour but sometimes for upward of two hours, depending on the style being brewed. During the boil, brewers add the hops at prescribed increments, depending on how they want those hops to affect the finished beer. The boiling action transforms the treasured alpha-acids in the hops, molecularly rearranging them into a new compound that provides the bitterness necessary to offset the sweetness of those unfermentable sugars produced during the mash.

The more the hops are boiled, the more pronounced the bittering effect, but the boil drives away the volatile oils that give beer it’s hoppy aroma and flavor. This is where the other hop additions come in: After the bittering hops, the next dose of hops (typically around 30 minutes into an hourlong boil) provides much of the hop flavor in the brew, while the aroma is achieved by adding a final dose of hops at the very end of the wort’s time in the kettle. In addition to incorporating the hops into the brew, the boil has a few other important effects. It sterilizes the wort and prevents spoilage due to wild yeasts or bacteria, and it drives off some chemical compounds from the malted barley that could otherwise have your beer tasting like cooked cabbage.

Fermenter

Once the boil is completed, the hot wort is separated from the mass of hop solids and coagulated proteins (a mess that looks like egg flower soup, called “trub”) and chilled from near-boiling to a yeast-friendly sub-70 degrees. This cool-down is usually achieved through a trick of thermodynamics in a piece of equipment called a plate chiller. The hot wort flows across wide metal plates in the radiator-like chiller while cool water flows in the opposite direction on the other side of the plates. This dual action of convection and conduction cools the wort effectively as it is pumped into the fermentation vessel where the yeast is added (or “pitched,” in brewer’s parlance).

The real magic of beer-making happens in these often towering fermentation vessels, and there’s a long-list of variables that brewers can tweak to affect the final beer. The most critical is the temperature at which the fermentation occurs, and nearly all commercial fermentation vessels are refrigerated to allow very fine control over the fermentation temperature.

Ales are fermented at between 60 and 75 degrees, and the yeast is most active at the top of the vessel, while lager yeast prefers to work at the bottom of the vessel between 40 and 45 degrees. Tiny changes in fermentation temperature can have big effects on the beer’s final flavor, and typically a warmer fermentation will result in more ester production and a fruitier beer. Hops can also be added at this point, and these “dry hop” additions will imbue even more hop aroma to the brew without imparting more bitterness. It’s a critical step in the production of the aromatic West Coast-style IPAs.

The typical conical fermenter used by craft brewers will range in size from 10-15 barrels (350-475 gallons) at smaller local operations and brewpubs to towering 800-barrel tanks that hold over 25,000 gallons of beer, like those outside of Firestone Walker’s Paso Robles brewery.

Bright tanks and packaging

In just a few days, the yeast will consume the fermentable sugars and create alcohol and carbon dioxide, and the liquid is now officially beer. Lager beers are left to cold-condition at near-freezing temperatures for a few weeks while the lager yeast metabolize some of the other byproducts of the fermentation — which is how lagers get their clean, snappy flavor.

An ale will be filtered, and this clarified “bright beer” transferred to a “bright tank” where it is carbonated and prepared for packaging in kegs or bottles (or, increasingly, cans). The packaged beer is then moved into cold-storage to await the fleet of distributors trucks that will bring the bottles and kegs to the markets and bars, and finally to your glass.