Physics can be a brewer’s best friend.
I came to this realization when someone first mentioned whirlpooling as a way to get clearer wort because it helps you leave excess hop-sludge and other solids in the kettle. Just set that thing to spinning and voilà, the solids form a nice cone in the center, and they mostly stay there when you rack to the fermentor.
That was revelation enough. However, soon thereafter I began to read about the whirlpool as a way to get some of the brightest, clearest expressions of hop aromas and flavors, and whirlpooling became a regular step in my process. That was a big deal for someone steeped in the brewing dogma of the two-thousand-and-oughts, which said that the 60-minute (bittering), 30-minute (flavor), and five- or 10-minute (aroma) hop additions were all we needed, besides optional dry hopping after fermentation.
So, what is this “whirlpool” step, why is it unique, and how do we do it?
Why Whirlpool?
There’s a truism that I share with any brewer who’ll listen when it comes to recipe design and process, and it’s this: In the boil, they’re ALL bittering hops.
Many still don’t seem to fully appreciate just how fragile hop oils are, believing that they can generate big hop aroma or flavor from boil additions alone. Yet if you’re boiling, you’re not only isomerizing alpha acids to create bitterness—you’re also rapidly volatilizing the oils that give us all those wonderful hop flavors.
How rapidly? Well, when Toru Kishimoto of the Japanese National Research Institute of Brewing tested various hop oils in 2008, he found that some—such as linalool, a common floral-scented compound—drop by as much as 85 percent in less than 15 minutes of boiling. Even the more robust oils burn off by a third or more in that same amount of time. If you’re boiling, even if it’s just for a few minutes, you’re blasting those oils and reducing their net impact in your beer.
Can you simply ramp up the amount of late hops used? Of course—but you’re also ramping up the IBUs while adding excess plant matter to the beer. That translates into lost volume plus a very real risk that your beer will taste like, well, lots of boiled plants.
Then there’s dry hopping—those cold-side additions of hops that aren’t boiled at all. That must be ideal for preserving hop oils and getting them into your beer, right? Well, not entirely; we certainly avoid volatilizing the oils, but we’re also introducing them in a way that greatly limits their solubility in the beer. That makes dry hopping a surprisingly inefficient method when it comes to adding (some) hop flavors. You’ll get hop character, for sure, and it’s absolutely essential for delivering part of that full spectrum of aroma and flavor we expect from an IPA. However, besides the limited extraction of hop oils, you’ll also get some grassy and resinous—and, if you go too heavy, vegetal—flavors, too.
That’s why whirlpooling is an excellent method if you want to unlock the full flavor potential of hops. By adding the hops after the boil—but while the wort is still hot—we maximize our extraction, greatly limit the damage we’re doing to the oils, and avoid creating overly bitter or frankly vegetal flavors.
How the Pros Do It
Like virtually everything else in brewing, there are a lot of paths to the top of the mountain. I hit up some of my pro brewing friends to see what their methods are, just as a jumping off point for our discussion. After we see what they’re up to, we’ll discuss the best approaches for us at home or in your nanobrewery. First, however, there are some commonalities among the commercial brewers I want to mention.
Most transfer from the boil kettle to a whirlpool vessel for this step—going through a port angled horizontally against the vessel wall, to get the wort spinning—rather than just whirlpooling in the kettle. The latter can lead to challenges in racking to the fermentors as we increase the volume of hops for these beers.
That point is likely related to the next point of agreement: Less is more. There is a common fear of overloading the equipment with hops, which leads to blockages and mucky transfers. In a world where “MOAR HOPS FLAVOR!” is a market demand and not just a competition to see who can get the most out of their ingredients, there’s a risk of going overboard. Cryo hops and extracts are two ways to get big character without substantial hop additions.
One aside, though: Don’t assume that more hops equal more hop flavor. Experiment results released by Sapporo found that their sensory panels detected more hop flavor from lighter additions, in some applications. Also, at some point, there are diminishing returns.
Where do methods differ? Mostly in temperature and time.
Among the pros I contacted, the method that probably lands closest to my own at home is that of Jeremy Myers, head of production at Bach’s Braumanufaktur in Neunkirchen, Germany. He prefers recirculating the wort between the whirlpool and heat exchanger until it is a pleasantly-warm-but-not-hot 165°F (74°C).
John Stemler, director of brewing operations at Chatty Monks in West Reading, Pennsylvania, says they use two different methods. In one, they start the whirlpool additions right away, at near-boiling temperatures: “At flameout, I toss in the whirlpool hops and recirc through my center port, which creates a ridiculous whirlpool all the way to the bottom of the tank. I do this for about three minutes, then switch to the side port to create the hop cone.” Alternatively, he sometimes chills to 185°F (85°C) before doing the above, “for hops that have a more delicate aroma spectrum.”
At Beachwood Brewing in Long Beach, California, Julian Shrago also has a “hot versus warm” split in his whirlpool methods. He says they go with 200–205°F (93–96°C) for their solidly West Coast core IPAs, such as Amalgamator. But they also do what Shrago calls a “coolpool” at lower temperatures—interestingly, adding cold water to the boil before transferring—for more aroma-driven IPAs, including their hazies.
Most pros allow the whirlpool to rest for only 10 to 15 minutes, but some go longer. Myers says their longer steep times at Bach’s are a function of their lower target temperature. “Usually, it’s no more than 15 minutes, but sometimes it’s as long as 45 minutes.”
That longer steeping period maximizes extraction at a “gentler” wort temperature, preserving the more fragile compounds. Likewise, James Gentile, head of brewing operations at Workhorse Brewing in King of Prussia, Pennsylvania, goes a bit longer, whirlpooling most beers for 20 to 25 minutes.
As with most methods, though, a home brewery is not a professional brewery. So, we need to do some translation.
Home Whirlpooling Tips
What follows is a process that will work. Whether it works best for your beers on your system is a different matter, though. So, as usual, I recommend trying this method to create your baseline, and then you can experiment to find what works best for you.
At flameout, chill your beer—or just let it sit, uncovered, if you don’t care to actively chill—to about 170°F (77°C). That’s low enough that volatiles are mostly going to survive, yet high enough to get solubility-stubborn compounds into your wort. At that point, get to stirring: You want a quick rotation, and 45 to 60 seconds of long sweeps around the outer edge of the pot should do the job.
Can you use a pump with an outlet angled horizontally on that edge (below the liquid line) to do the same job? Sure. And if you’re counterflow chilling, you can kill two birds with one stone here, but it’s not a requirement—the spoon is up to the task.
While you’re at maximum rotation, add your hops—which will gather in the center of the kettle—and rest for 10 to 20 minutes, erring on the longer side if you’re shooting for more myrcene (piney) or caryophyllene (woodsy) flavors, as these are notably low in solubility. As you adjust this process based on your own feedback and evaluation, note that time and temperature will generally be inversely proportional: If you bump up your whirlpool temperature, ease back on the steeping time; with lower temperatures, go longer.
Whether to cover the kettle seems to be a matter of some debate. However, unless you have notable issues with DMS in your beers (in which case, leave it uncovered), I doubt it makes any discernible difference.
Some practical process considerations remain. First, to underscore a warning from the pros: Be careful when running off from the kettle because hops love to jam up filters and tubing. Add only the hops you need, run off from a clear section of the wort, and avoid agitating the cone you developed in the whirlpool.
Second, some say they don’t want to bother with the added time needed for whirlpooling. If that’s you, you can always “short boil” your wort for 40 minutes instead of 60 and buy your time back.
Finally, all-in-one brewing systems are perfect for whirlpooling: Just program it in, and the existing circulation system handles the rest. If you’re on the fence about trying out one of these machines and you do a lot of hop-forward beers, this could be the feature that gets you off the fence.
Hops Considerations
Let’s also consider our recipes. How much is the “right” amount of hops for a whirlpool addition? I typically go for a level ounce (28 grams), sufficient for even my hoppiest beers. There seems to be a real “diminishing returns” situation with whirlpool hops, and for all the reasons noted above, there’s no virtue in going overboard. Also, like any other hop addition, whirlpool hops will result in a bit of ingredient-based volume loss, so plan accordingly.
Then there’s the question of IBU adjustment: Should you “count” those whirlpool hops in your IBU budget? In all but the lightest/sweetest beers, the answer is … probably not, especially if you’re going low-and-slow as I recommend above. The isomerization of alpha acids drops off dramatically when we get below boiling temperatures. The Beersmith software calculates just 20 percent utilization at 170°F (77°C), and we’re talking about only 15 minutes of contact time. A particularly long, particularly warm whirlpool might increase bitterness slightly—but it’s not something I sweat (and adding whirlpools to my existing recipes didn’t turn them bitter).
Finally, there’s the choice of hops and how they’re deployed elsewhere in the recipe. Any flavor/aroma variety is appropriate for whirlpooling, but this is a case where freshness matters. Hops are surprisingly durable, and I often don’t hesitate to use “older” hops from a previous harvest year in the boiling or dry hopping stages. However, if I’m whirlpooling, I want the freshest hops I can get. In side-by-side comparisons of my Iron Dice amber ale, there was a noticeably brighter fruit character in the fresher-hops batch, and I was sold.
As for the question of boil, whirlpool, and/or dry hops: If it’s an IPA, I say, “Do them all.” Covering that flavor spectrum helps you get a genuinely hop-forward result. For other styles, though? I reserve dry hops for beers that want that herbal, balsam quality. Try swapping in whirlpool additions for dry hopping on all your non-IPA styles and see whether you don’t like the results better.
Not Just for IPAs
That brings me to one final point: Whirlpooling is not just for IPAs.
I whirlpool pilsners, altbiers, American blondes, English bitters—it’s especially great for getting the earthy-woody-fruity hop character that makes cask pale ales sing—and more. Some of this is simple convenience—I brew on a machine that makes whirlpooling a simple matter of a few keystrokes. But it’s also unquestionably true that it’s made my beers more enjoyable.
Of all the brewing ingredients, none is more of a mystery than hops, which may partially explain why IPAs of a dozen or more varieties not only exist but dominate the beer landscape. Anything that wrings more of those flavors out of a brew day is a powerful tool, and for brewers with just a bit of patience, the whirlpool does exactly that. Nothing is more likely to develop your appreciation for—and, maybe, love of—hops better than whirlpooling.