A Simple Guide to Hop Charges

Refreshing Summer IPA Craft Beer with Hops
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Traditionally, hop usage was to generate a supporting bitterness to cut through residual malt sweetness, adding a pleasing, subtle aroma to the beer. The other purpose was as an anti-spoilage agent. Compounds in hops slow the growth of Lactobacillus, arguably the most aggressive spoilage mechanism, which actually explains hops’ rise to the throne of beer additives. It’s way more cost effective to be able to sell palatable beer for longer after all.

When we normally talk bitterness in beer, people wave around the IBU (International Bitterness Unit) as the holy sacrosanct measure of bitterness. You see it in every recipe calculator and beer menu boards. But the IBU isn’t the end-all and be-all, in fact it’s a terribly wibbly idea to begin with.

First, the IBU is supposedly a measurement of dissolved isomerized alpha acids, the potent bittering compound generated by boiling hops in wort. How much of your hops’ natural alpha acid content has been flipped to a water-soluble, bitter molecule; iso-alpha acids. Technically, it’s a measure of absorption of light at a specific wavelength, but for most of us it’s the number spewed out of a complex equation that our brewing software runs. 

But the actual creation of isomerized alpha acids — often called hop utilization — in your wort is a nightmare to correctly predict and fraught with multiple variables. Those include, but are not limited to:Kettle geometry, type of hop product (pellet, cone, extract, etc.), wort pH, wort gravity, and hop storage conditions (how old are your hops, how have they been stored, how were they packaged — alpha acid numbers are not always correct).

As homebrewers, our actual knowledge of what we’re generating in the kettle is practically limited. That’s not to say that the IBU calculation is completely useless, but understand that the important measure is what you taste, not what some number indicates. Learn what XX IBUs tastes like to you (Sierra Nevada Pale Ale is pretty spot on to 35 IBUs, for instance) and then learn what that IBU level (calculated) looks like in your brewery. Work relative to that. 

As for the calculation, remember that the most used homebrew formula for hop bitterness, the Tinseth formula, was developed by Glenn Tinseth using freshly analyzed whole leaf hops on his homebrew system. The equation was fit to the data he collected. In other words, it works absolutely perfectly for a homebrew rig that no longer exists with hops long since used!

But, the actual creation of isomerized alpha acids — often called hop utilization — in your wort is a nightmare to correctly predict and fraught with multiple variables

The question of perceivable bitterness is also colored by the fact that many compounds beyond isomerized alpha acids taste bitter. Be aware that hops contribute other compounds that affect our perception of bitterness, but don’t change the measurable IBU level one tiny little bit.

Hops in the Kettle

Chuck them in and let them roll — that’s all you need to do with your hops, right? Mostly. With increased use of hops, particularly in whirlpool (post-boil) stages, brewers have pursued the removal of extraneous matter by resorting to a number of in-kettle straining setups to prevent hop matter from leaving the boil vessel. Denny and Drew both rely on the strainers built into their Grainfather kettles. 

Some brewers will use filters around any output tubes/spigots and others will constrain the hops themselves. The two most common being hop bags (mesh bags that you add your hops to before tossing into the kettle) and hop spiders (think a mesh basket that hangs into the boil). Concerns abound about the impact that the restricted movement of the hop material can have on isomerization. (And there’s plenty of evidence that shows it can lower the amount of generated IBUs.) Our word of advice if you use these methods — don’t stuff your bags full or your hops won’t get entirely wetted (particularly true when dry hopping) and don’t sweat the change. Again, learn how your beer tastes and adjust from there.

Bittering Charge — It does what it says. This is the charge where you generate bitterness most efficiently since isomerization is greatly impacted by time above the isomerization threshold (~170 °F/77 °C). The more time, the more bitterness generated (to a point — there is a threshold of diminishing returns and overunity in hops is as fantastical as in motion). Once you cross 90 minutes, you’re not gaining enough to make the extra energy use worthwhile. In fact, older studies demonstrated that boiling hops for over 120 minutes can lead to undesirable flavors.

Traditional timings for a bittering addition lie between 60–90 minutes. (Ranges are “ish” because time is a loose construct of minds desperate to control an unraveling universe.) 

Brewers will typically offer the advice that hop variety in your bittering charge doesn’t matter because you’re boiling off your aromas and flavors. We’d still advise care when selecting a hop since you usually want to reduce vegetative matter in the kettle (leafy flavors and wort absorption) by using a high-alpha variety. Drew tends to use a lot of Magnum and Warrior, for instance. We’d even argue that hop variety can still impact flavor perception and that’s why we’re both fans of using a bittering charge of Chinook in a classic West Coast IPA to provide an extra bite.

Bittering additions can vary between less than a quarter of an ounce (7 g) — Drew’s Mild can use as little as an eighth of an ounce (3.5 g) depending on the hop choice — to a couple of ounces (~60 g) for your beers that need a bold, bitter bite. 

Flavor Charge —This 20–35 minute charge is arguably the most controversial and least used. The intention “blow off the aroma and generate some bitterness while preserving flavor” firmly lies astride the usual path of hop perception modern brewers crave. 

Our advice — unless you have a real reason to need this addition, or you just want to be ultra traditional, you can safely skip the flavor charge for the . . .

Aroma Charge —This is where things get exciting and make the craft beer lover and hop head perk up. 10 minutes and below are the land of all the aromas and flavors and less bitterness production (although not none). This is where we start to see the loading in of your more exotic varieties – things of rarer availability or strange experimental numbers. The idea is to start dissolving oils and making them available in the near future to your nose. If you add them at the boil’s end and proceed directly to chilling, you’ve added them as “flameout” or “knockout” hops.

A couple of ounces (50–100 g) per five gallons (19 L) can perk up and load a beer with all the smells, but . . .

Whirlpool Charge — A funny thing happened on the way to the IPA party and brewers began trying to fill their beers with as much flavor and aroma with less bitterness. (The super bitter IPAs of the Aughts turned off a lot of potential IPA drinkers). Since high-alpha hop varieties (the other trend has been increasing alpha acid content in hops) can generate loads of IBUs with a mere glance at a boil, brewers have increasingly reduced the amount of time in boil conditions they expose their hops to. The hope – less bitter, still brightly hoppy and aromatic beer. 

To this end, and accelerated by the haze craze, a number of beers are produced with almost no hops added to the boil. Instead, they wait until the boil ends and add major charges (ounces and ounces) of the hops to wort fresh off the boil or purposely chilled (to ~170–180 °F/77–82 °C) and let the hops sit in a swirling mass of hot wort for 20–30 minutes. Since the wort is still above 170 °F (77 °C), you’re still slowly generating IBUs (as are any previous kettle additions) while extracting aromatic compounds from the hops. 

Drew likes to whirlpool for his IPAs and pale ales while getting his first beer of the brew day, while Denny has tried the technique many times and eschewed it in favor of . . .

Hops In The Fermenter

Simply put, dry hopping is the addition of hops to the beer during or after fermentation for several days to release aromatic compounds into the beer. When to add depends on the impact you want to have. You may have heard of “biotransformations” — that exposing hop compounds to actively fermenting yeast will cause various constituent oils to be transformed by yeast activity into compounds that smell and taste different. Example: The hop compound geraniol (flowery) can be enzymatically transformed into citronellol (citrus, fruity). 

This is a very popular technique with hazy IPA production. Commercially, brewers are pushing the amount of time in contact with the yeast to shorter times (1–2 days prior to the beer being complete) to allow them to harvest cleaner yeast, so it doesn’t take very long.

For more classic dry hopping, you wait until the beer is fully fermented and all yeast activity has ceased. Add the hops and let it sit for a period of time before serving. (In traditional cask service, the hops would be bunged into the cask and allowed to stay in contact until the cask was emptied. In keg practice, we typically remove the hops before kegging and serving).

Old school dry hop times were on the order of 7–14 days or longer, but studies show that dry hopping efficiency peters out (and starts re-absorbing oils/isomerized acids) after 2–3 days when using hop pellets. Temperature can also impact what flavors get extracted (35 °F/2 °C, for instance, favors the extraction of linalool).

Another old belief about dry hopping is that it adds no bitterness to the beer but this turns out to be less than true. Not only can you pick up astringency (a flavor often confused for bitterness) from the hop leaf material, you can also pick up bitterness from oxidized alpha acids called humulinones. They’re mildly bitter but at the massive dry hop rates we see today, both the tannic astringency and contribution of things like humulinones adds up quickly.

One thing we haven’t covered yet is how to choose the hops that you use and when you use them. We recommend starting with the Yakima Chief Hops “Survivable Compounds” handbook.

Issue: March-April 2023