Beer Fact Friday: Whirlpool
For the past few weeks, we’ve been working our way through every step of the brewing process. You can head back through our past Friday posts for the full overview, but here’s the short version: We cracked open our malted grain (Milling), combined it with hot water to extract its sugars (Mashing), separated the liquid wort from the grain (Lautering), and brought the liquid up to boiling temperature while adding hops (Boiling). For the next stage, it’s once again time to separate our liquid from any large particles, such as hop matter, that might be floating around inside it. But, rather than the perforated false bottom we used to separate liquid from solid during the Lautering stage, this time we’ll use a little physics.
Remember the scene in that one pirate movie during which two ships are caught inside a giant vortex of water and the ships are drawn, steadily and inexorably, toward the maelstrom’s terrifying center? That’s kind of what’s happening inside the whirlpool tank. Once you get a liquid spinning enough to create a whirlpool, centripetal force causes any solid particles to naturally migrate toward the center of the cone. In the movie, those “solid particles” were ships full of unwashed scallywags; in our case, they’re large pieces of hops.
The whirlpool effect is achieved by pumping the wort into the tank at an angle from a tube toward the top of the tank. As the hot wort swirls, solids gather into the center, forming a cone of “trub” (the name for sediment containing hop fragments and other protein-based particles) and leaving the rest of the wort clear. Once the wort stops spinning, it’s pumped out of the whirlpool vessel, leaving a big, gooey pile of trub that can then be tossed in the trash or a composter.
The whirlpool is both a process and a brewing vessel, which means the Whirlpool stage usually occurs inside a dedicated Whirlpool tank. However, many breweries carry out the Boiling and Whirlpool stages of the brewing process inside the same vessel.
After the wort’s clear and the trub is removed, it’s time to cool it off. We’ll cover that stage next week.
Beer Fact Friday is our weekly exploration of the topics that make beer the world’s most interesting beverage. Check back here next week—or follow us on Facebook, Instagram, or Twitter—for more fascinating beer trivia.