Hopheads unite, everything you wanted to know about dry hopping beer.

Hazy, Juicy, Murky, whatever you call it, these IPAs are here to stay.

Hello again fellow fermented friends,

In the world of beer, hops have always been an essential ingredient. Hop plants (Humulus lupulus) have been cultivated for centuries for their aromatic and antimicrobial properties they impart to beer. From the mild soft bitterness of English hops, to the giant juice-bombs of some American varieties, the plant is now domesticated on every continent except for Antarctica, and in many places they also grow wild (sometimes called hobo hops).

While there has always been hops in beer, the rate at which they are added to beer and time during the brewing process has changed wildly from decade to decade. First off, let’s talk about basic brewing knowledge. A typical brew is created when malted barley is crushed and steeped in hot water until there is an enzymatic conversion of long sugars into shorter sugars. The sugar water is then separated from the grain and vigorously boiled to further breakdown the sugars and to sterilize it. Traditionally, hops were added at the beginning of the boil or at different times during the boil depending on the desired final bitterness and aromatics of the beer. Cooled sugar water (called wort, but pronounced wert) is then transferred to a fermentation vessel where yeast is added (called a yeast pitch). Yeast convert sugar to alcohol and carbon dioxide, as well as transform a number of bioactive compounds found in hops, and malt into other compounds with unique flavors and aromas.

Boil hopping, (also called “hot-side” hopping), is typical of many beer styles, but none more than pale ales and West Coast style India pale ales. The pale ale was basically invented by Sierra Nevada as a hop forward ale with high drinkability (read: a simple 2-row malted barley grain recipe and fermented by a yeast with very little added character). This classic beer was workshopped by famed brewer Ken Grossman over many, many batches, until he hit on that special recipe that has remained one of the most popular and consistent beers ever to hit the planet. The classic west coast IPA that followed in this footprint, was quite similar in recipe and fermentation, but typically had more hops added during the boil and a much more aggressive bitterness.

Now unless you have been off-world for the last couple decades, then you probably know that craft beer is currently inundated by a very different sort of beer: the hazy IPA (also known as East Coast Style IPAs). This style is characterized by the eponymous opaque texture, less aggressive bitterness, and an overall more rounded flavor reminiscent of various tropical fruits, or dank herbs, (for more on beer styles see the current Beer Judge Certification Program BJCP guidelines). These strong aromas and flavors come from a special type of hopping schedule called dry-hopping. Dry-hopping refers to adding hops to a beer at anytime after the beer has been cooled down and transferred to a fermentation vessel. This type of hopping while the beer is at fermentation temperature doesn’t release bitterness, instead it releases the aromatic compounds known as terpenes and thiols. Terpenes like linalool give lavender its wonderful floral aroma, and many of the terpenes we know from herbs and fruits are also found in hops. For more in depth look at terpenes in beer, see this 2008 article from the Journal of Plant Physiology.

Another important flavor compound found in hops are called thiols. These sulfur-containing compounds make up less than 1% of the essential oils in hops, (and are also present in malt to some degree), but they are vital for some of the strong fruity, tropical, and resinous fragrances and tastes of dry-hopped beer. For an in-depth look at thiols and other flavor compounds in beer, check out this great review article from Holt and colleagues from 2018. As an added bonus, thiol compounds have high antioxidant properties which can help keep beer oxidation and staling at bay. For a more technical explanation of thiol abundance and beer staling, check out this post from Marianne Lund at the 2012 conference of the Master Brewers Association of the Americas.

The Essence of Haze

It sounds pretty simple right? Just throw the hops in the fermenting beer and you get hazy juice bombs any bro would love to crush. Well, it is a fair sight more complicated than that.

First of all, the stable haze in the beer is almost completely dependent on two things: dry-hopping and high protein content. Hop compounds called polyphenols can interact with malt proteins to maintain haze. Hazy beers brewed with cereal grains that contain a high protein content, such as malted oats, flaked oats or spelt have a nice creamy mouthfeel, and also participate in haze formation. Commercial brewers and homebrewers alike use about 20% by weight of these specialty grains in the total recipe (for a rousing read on barley analysis and genetics, please read my friend Dr. Huitema’s post at the Beerologist.)

Secondly, (and I know I might get some flack for this), the yeast strain chosen to ferment the beer will have everything to do with the final aroma and flavor and almost nothing to do with the haze. Because all brewers will cold crash their beer prior to packaging, the majority of yeast cells will drop to the bottom of the vessel and are usually discarded or harvested to use in another batch. Many commercial breweries also use large centrifugation technology to separate yeast from finished beer prior to packaging. Some yeast strains do stay in suspension better than others (think unfiltered German Hefeweizen), but the haze in IPAs is mostly generated by the protein content of the grain used and the polyphenols released from hops.

Finally, the ultimate predictor of juicy flavor in a beer is the strain (or cultivar) of hop used. From the start, hop brands such as Citra have been consistently used to create a more aromatic and citrusy, tropical beer, while other brands like Cascade and Simcoe offer a flavor typically described as dank or cat pissy. I know, I know, both of those descriptors sound terrible, but these brews can actually be very pleasant if done correctly.

How to dry hop like a pro:

If you are a homebrewer, you are probably a dedicated hobbyist that has worked out a very specific method to make the biggest, haziest, juiciest beer ever. In reality, dry hopping at home is a very simple process, but for many it can be tricky to get the final product right.

Here is how I do it at home:

Once your beer is fermenting away (active gas release) continue to monitor fermentation visually until the activity starts to slow slightly. With a healthy addition of yeast at the correct cell concentration for your wort, standard fermentations occur within 3-4 days, finishing visually active fermentation within 6 days and then maturing for a further 6-7 days. Once you know the general timeline for your particular beer, add hops directly to the fermenter with some activity still showing (usually day 3-4). Allow the beer to finish maturing, and then cold crash the beer from fermentation temperature to about 33-34 degrees F for at least 2 days. This cold crash will help to drop out the green vegetal material and improve your yield. Allowing your beer to sit with hops for longer than the maturation of the yeast will give grassy notes to your beer that are undesirable.

Use hops that have been stored cold and vacuum sealed to yield best results. Assuming your fermentation volume is at a minimum of 20 L or 5.3 US gal and has a venting system to let gas out (please, please always allow gas to escape!), do not worry about oxygen ingress during hop addition, as long as there is activity in the vessel the yeast will cleanup any oxygen present and off-gas it as carbon dioxide. From there, package as you normally would, while avoiding the green hop material at the bottom of the vessel in the final package, as this gives aggressive bitterness. From this schedule, I have made some really delicate hazy IPAs with strong tropical notes and have never had stale oxidized flavors. It should be noted that I package from carboy to keg with a racking cane and then purge kegs of oxygen immediately after the transfer. My kegs also don’t last that long (1-2 weeks) on tap because they are so tasty. If you are trying for long-term flavor stability you will need to evaluate your oxygen situation individually.

Here is how I do it at work: The process follows the same timeline as above. Wait for active fermentation to slow or stop then add hops. The difference at the commercial scale is that everything is tightly controlled to essentially eliminate chances of oxygen and contamination entering the system. Most production breweries trying to make hazy IPAs will probably just open up the top of the fermentation vessel and throw the hops in. DON’T DO THIS, UNLESS YOU WANT A BEER SHOWER! But honestly, it is quite dangerous to use the top manway cover to dry hop and can result in loss of expensive product.

Instead, use a dedicated hopping vessel that you can hook-up inline to your fermenter and a recirculating pump.

The first picture below shows the direction of flow of the recirculating beer. The orange hose is used to draw from the tank and the grey hose on the bottom is used to pump hops and beer into the tank from the bottom. The extra hoses coming off the sides of the pictures are labeled CIP and are used to clean the circuit before and after hopping. The second picture below is of a 31 gal (1 bbl) vessel known as a hop cannon. It can be used as a small fermenter, but in our case we typically clean-in-place this vessel and sanitize it, then purge it with CO2 prior to adding hops. The beer is then recirculated through the pump and through the hop cannon before being sent back into the fermentation vessel.

Final Notes

First off, as with all content I post, these views are my own and do not represent any company or institution I am, or have been affiliated with. These are just my suggestions for what has worked for me in the past. There are likely many other ways to dry-hop that work well, and I am sure there are better ways to do this depending on your scale of brewing.

Hazy IPAs are a part of craft beer culture and should be accepted for their strong hop forward character and interesting tasting notes. The biochemistry of the haze formation and the flavor development should also be celebrated as a monument to brewing science developments in the last few decades.

If you do dry-hop, try to limit oxygen ingress as much as possible and use the active yeast fermentation to your advantage, but don’t kill yourself trying to make the perfect closed system at the homebrew level. Remember you will always diminish the final yield of your beer when adding hops in the fermenter. The hop material will suck up beer and you may lose up to 30% of volume depending on hopping rate.

Choose your hops the same way you would use seasoning in a cooking recipe. Remember that they will combine to create unique flavors and aromas that may not be possible by single hop additions.

Lastly, the yeast strain chosen for fermentation can have a significant impact on the overall flavor and aroma of the beer. Remember those thiol compounds I talked about present in hops and malt? Well certain strains of yeast can actually produce enzymes which cleave these thiols from the plant material and make them accessible for your taste buds (called biotransformation). There is a budding industry of genetically modified yeast strains which can amp up the cleavage of hop thiols, so that brewers get more bang for their buck and avoid product loss from using excessive amounts of hop vegetal matter. There is a great article here from Denby and associates which details the process of genetic engineering brewing yeast to improve thiol release and the company formed around this technology Berkeley Yeast is just starting to scratch the surface of the potential for genetically modified yeast to improve brewer’s livelihoods and make beer drinkers happy to haze it up for years to come.

Thanks, hope you enjoyed the read and see you next time,