Timing matters. In hopping, it matters because we’re doing a delicate dance that extracts distinctly different things from the hops, and getting more of one usually results in getting less of the other. I’m speaking here about the productive tension that exists between hops oils and hops resins/acids. You have a hop cone. Inside of it are oils, which we generally think of as being the flavor-producing agent.
You also have alpha and beta acids which, when isomerized or oxidized, add bitterness. The trouble is that isomerizing alpha acids is accomplished by boiling them, and boiling drives off the chemicals that make our hops oils so flavorful. This means that we have a construction challenge when it comes to producing beers with both bitterness and flavor—or one and not the other—and knowing what you’ll get out of hops based on when they’re added to the beer is essential to producing the beer you want.
In short, the longer your hops are exposed to heat—and the higher the temperature—the more likely it is that you’re getting bitterness and not flavor, and it may be happening faster than you think. Of the potential bittering you could get out of the hops you add, a majority is produced in just about 20 minutes. At the same time, most hops oils deplete by half or more with just 15 minutes of boiling. Linalool, a lavender aroma–producing hops oil, reaches 50 percent depletion in just 6 minutes.
The upshot here is that even short-added hops still yield most of their bittering potential and lose most of their flavoring potential. If you want to have a better chance of getting bigger impressions of those hops oils in your beer, then you need to look beyond the boil.
When?
Let’s take a walk through the brewing and fermentation process and examine the role hops tend to play when—and the roles they likely won’t or can’t.
Mash Hops. Nothing stops us from adding hops in the mash, but your expectations for either bittering or flavor should be modest. You’ll likely yield a few IBUs from isomerization (the mash is, after all, warm if not hot), and especially if you use pellet hops, you may get some pulverized plant matter carrying over into the boil where it can then impart some isomerized alpha acids—it just won’t be much. Likewise, only the most robust of hops oils will have a chance of surviving the boil, so extracting them here probably won’t produce noticeable flavors.
First Wort Hops (FWH). Once upon a time, we were told a story of how “first wort” hops—those added to the kettle while the lauter and/or sparge were running off—added to the beer unique flavors or bitterness of a different, softer character. Having looked for empirical evidence of this, I have to say that it’s pretty thin. I suppose it’s possible that, in some recipes and on some systems and in some contexts, FWH can have desirable flavor impacts, but I’ve seen nothing to suggest that it’s broadly generalizable. However, there is data to suggest that FWH consistently adds more IBUs to the beer. The longer exposure to higher temperatures squeezes out a small increase in utilization of alpha acids and, therefore, juices the measured IBU count. If you’re making a beer that should have firm bitterness, it’s probably not a bad idea to add your early-boil hops as first wort hops, if only to err on the side of “more bitter.”
Boil Hops. Conventional wisdom among brewers was (and probably still is) that hops added at the start of the boil are your “bittering” hops, those added at about 30 minutes remaining are your “flavor” hops, and those in the final 10 minutes or less are your “aroma” hops. That’s probably not a productive or accurate way to think about it. Given the quick-start nature of both alpha-acid isomerization and hops-oils volatilization, I find it better to assume that in the boil, they’re all bittering hops. Adding them later in the boil (especially in the final 10 minutes) will certainly make it more likely that some hops oils survive and that some potential bittering won’t materialize, but if I’m looking for medium-high or prominent hops flavors, I’m adding hops post-boil. The impressions will be there, but they’re not nearly as likely to be as bright, crisp, or notable.
Post-Boil Hops. If you’re concerned about boiling away your hops oils, you can always just wait until you’re done boiling to add those hops. We have essentially three ways to add post-boil (but pre-chill) hops: flame-out, whirlpool, and hopback.
Flame-out hops are just that: when you kill the heat, you toss in your hops. You’re still over the 170°F (77°C) threshold that will act to volatilize your various hops oils, but they won’t be at full-boil temps, nor for very long, which should mean greater odds of survival for the extracted oils.
Whirlpooling is the practice of stirring your wort to form a whirlpool that will gather solids in the center of the kettle to aid in getting a “clean” runoff, and it’s possible to use this time (especially if you wait for the temperature to drop) to add flavor and aroma hops that will preserve almost all of their character. Experimental studies find that the longer you allow the hops to rest in 140–170°F (60–77°C) wort, the greater the flavor impacts.
Finally, you can also employ a hopback, which is a device that you pack with whole-flower hops that are then “washed” with the post-boil wort en route to the chiller. Any (or, even, all) of these methods are preferable if your goal is big hops aroma and flavor: you’ll add a nominal number of IBUs but extract and preserve more hops oils.
Dry Hopping. Post-chill hops are typically referred to as dry hops. Dry hopping is a common practice among homebrewers and professional brewers, but not all dry hops are the same. Adding dry hops at the start of primary fermentation has been shown, in some basic experiments, to yield less flavor than adding them post-fermentation.
Using more than one hops variety can also add more flavor. In addition, multiple dry-hop additions seem to impart more overall flavor than simply adding multiple varieties of dry hops all at the same time. On a personal note, my own experiments in this area have shown no noticeable difference between a “replacement” method (adding and then removing each bagged dry-hop addition in sequence, so there’s only one dry-hop variety in there at a time) and an “additive” method (adding dry hops in stages but simply leaving the initial dry hops behind), so feel free to free-add your first dry hops, then subsequent additions in succeeding days, without removing the initial additions.
Dry hopping adds hops oils, obviously, but no measurable IBUs, since there’s no heat involved. This does not mean, though, that no bitterness is added: extracted beta acids impart bitterness if/when they ultimately oxidize, and if you use a large enough charge of hops, this bittering may be noticeable, especially in beers that seek to avoid it. Dry hopping also often adds a resiny flavor to the finished beer, which you should take into account in your recipe design.
Post-Packaging Hops. Since I have been asked this, sincerely, on multiple occasions, I’ll answer it. You can add hops to the bottle at packaging. But why would you want to?
How, What, and Where?
All of the preceding is dependent, to some greater or lesser degree, on the specific hops you’re using.
The form of the hops can be whole flower/cone, pellet, powder, extract, and even “hash.” Whole-flower/cone hops use the entire hops cone, and some believe that the unprocessed plant material imparts subtle authentic flavors. Pellet hops have been ground and “standardized” into homogenous pellets by grinding the hops flowers and then forming them into pellets that break apart in the boil. This process results in additional exposed hops surface area, increasing access to the oils and resins/acids in the hops. Hop powder is a concentrated form of only the hops resins and acids, and early impressions are that it can (at least early in a beer’s life) add much more pronounced flavors than are possible with traditional flowers/pellets. Other extracts are available as well, in the form of gelatinous hops liquids containing both resins and acids, and even pure isomerized alpha-acid extract. Know what form you’re using and choose based on your desired outcomes.
Whichever form you choose, composition matters as well. Not all hops varieties are identical, of course, but even within strains and within harvests, you’ll find varying (but measurable and measured) concentrations of alpha acids, beta acids, and a wide range of hops oils. Savvy brewers can select hops with greater proportions of the elements they want, whether it’s super-high-alpha- acid hops to minimize the amount needed to bitter a Double IPA or a caryophyllene-heavy hop for that woodsy, rustic Cal Common recipe.
And let’s not neglect the hops’ point of origin. Terroir is a concept more common to winemaking than brewing, but there is absolutely no question that climate, soil composition, and growing condition variations that are part of the hops-growing process have a substantial impact on their flavor. American Hallertau is simply a different hop from German Hallertau, and we should consider hops geography when we plan out our recipes.
Simply put, the “how, what, and where” of hops matter.
Purposeful Hopping
Hops are a key component of beer—maybe the key component of beer—and we owe it to the beer to use our hops purposefully, thoughtfully, and deliberately. A good grounding in what hops add to our beer based on when we add them to the beer is a valuable and useful thing. It allows us to set realistic expectations of the likely flavor profile we’re going to get. It makes it possible to make meaningful changes to recipes and processes when we seek to incorporate our impressions and feedback. It also increases the odds that we can make that “perfect” beer a second, third, or tenth time when we want to because we’re aware of how the composition and use of our hops made it the way it is.
All of this should carry an important disclaimer, however: try, then trust. We know too little about hops, and though that base of knowledge is increasing quickly, a wide range of recipe- and system-specific factors can make your mileage vary. Water chemistry, burner and kettle geometry, ingredient interactions, and more can all blunt or amplify different elements of hops flavor and contributions. Brewing is, after all, still as much art as science. A thoughtful and purposeful approach to hops and hopping will minimize your learning curve rapidly. Best of luck, and good hopping to you.