Dry Hopping for Great Aroma

If you want your beer’s hop nose to knock your socks off, maybe it’s time to try dry hopping.

Dry hopping is the process of adding hops to beer at some point in the process well after fermentation has begun. Dry hopping imparts a fresh hop aroma to the beer without adding any bitterness. It also adds a unique taste character.

Adding hops later in the process preserves the flavor and aroma from the hops’ oils. These are distinct from the alpha acids that give the beer its bitterness. The oils add no bitterness, just flavor and aroma. During the boiling process, nearly all of the hop oils evaporate; the longer the boil time the more oils are lost. The hops put in at the beginning of the boil for bittering lose almost all of their oils. Those added near the end of the boil don’t lose as much oil but still lose quite a bit. And the heat of the boil induces chemical changes in the oils, so even those that are left lack the aroma of fresh hops.

So if we want to add hops to impart a fresh hop aroma to the beer, when is the best time to do it? Traditionally, dry hopping was done in the serving cask. A charge of fresh hops would be added to the cask right before the bung was hammered in. If you keg your beer, you can add the hops to the keg. This gives the beer the best and freshest aroma. But what if you bottle? It makes sense to take a step backward in the process and add the hops to the fermenter. But there is a right time and a wrong time to do it.

The Right Time

The right time to add the hops to the fermenter is just as the fermentation starts to slow down. This is usually apparent by the head (or kraeusen) starting to diminish, which usually coincides with a decreased bubbling in the airlock. Typically this will be three to four days after fermentation has begun. If you use a single-stage fermenter, just add the hops. If you use a secondary fermenter, rack the beer now and add the dry hops to the secondary.

The wrong time to add the hops is at the very beginning of fermentation, or close to it. Hops are not a sterile product and putting them in too early can cause a contamination in your beer.

If you wait for the right time, several factors are at work in your favor. The beer’s pH will have fallen to the point where the organisms on the hops can’t survive, and the alcohol now present also serves to kill them. You also have a healthy yeast population in your beer, and this yeast will tend to starve out the other organisms. There is no risk of contamination from dry hopping if you do it at the right time.

The final good reason for waiting is that during the initial stages of fermentation large quantities of CO2 are being generated, and this will scrub the hop aroma right out of your beer.

Pellets or Whole Hops?

How you dry hop depends on what type of hops you are using (pellets or whole), and where you are dry hopping (keg or fermenter).

As far as dry hopping is concerned, there are some major differences between using pellets and whole hops. Pellets initially float on the surface but eventually settle to the bottom. Whole hops float on the surface nearly all the time.

The hop oils are contained in the hops’ lupulin glands. These have been ruptured in pellets but are largely intact in whole hops. All of the hop oils are available to get into the beer almost immediately with pellets and may take a week or two to get a decent amount of oils released when using whole hops.

One note about pellets: Sometimes adding pellets can appear to kick fermentation into a higher gear for a while. While this is sometimes a consequence of rousing the yeast when stirring in the pellets, it is most likely just CO2 being released. The pellet particles become thousands of bubble nucleation points and cause lots of CO2 to come out of solution. So be prepared for this!

Fermenter or Keg?

Let’s take the fermenter case first. If you add pellets to the fermenter, eventually they will sink to the bottom. The hop oils will be released into the beer in a few days, usually by the time the hops have settled out. All that you have to do is carefully rack the beer off the yeast and hop sediment. A rule of thumb is to leave the pellet hops in the beer for at least a week before bottling. This gives them time to settle and time for the aroma to become infused.

If you use whole hops in the fermenter, they will mostly stay on the surface. This makes it easy to rack out from under them — they will float down on the surface of the beer as you transfer. But the disadvantage is that a good portion of the hops’ surface area is sticking up in the headspace and in that position they’re not imparting anything to the beer.

The solution is to put the hops in a mesh bag and then weight the bag so that it sinks. Marbles are a popular item to use as a weight. But it takes a good handful of them, not just a few. Whatever you use, make sure it can be sanitized and won’t react with the beer. Don’t use lead fishing weights! You will want to leave whole hops in the beer for at least two weeks.

If you are adding hops to the keg, you’ll definitely want to contain them somehow. If you’re using pellets, a bag-and-weight system is a great idea. Otherwise you’re going to keep sucking pellet particles through the dip tube and they’ll surely clog the keg connectors. If you are using whole hops, you can use almost any fine mesh bag, but don’t pack the hops too tight. You want the beer to mingle with the hops. As with using the bag in the fermenter, you’ll want to weight it somehow. Or a handy tip is to wedge the bag between the keg wall and the dip tube, as near to the bottom as possible.

If you use pellets, you’ll notice that the hop aroma and flavor in the beer can be overpowering at first. Because the lupulin glands are burst, all the oil goes into the beer at once. Just be patient and it will mellow out. On the other hand since the beer is usually cold, the hop oils are released very slowly from whole hops when they’re in the keg. This acts like a time release effect and keeps the aroma level reasonably constant over time.

How Hoppy?

Like almost everything in brewing, how much hops to use when dry hopping depends on a lot of factors. How hoppy do you want the beer to be? What kind of hops are you using? What is their oil content? Where are you dry hopping? How much time do you have? What is the temperature?

You’ll have to determine on your own how hoppy you like your beer. Some hops have a more potent or distinctive aroma than others. This relates in part to the amount of oil they contain but also relates to a particular variety’s aroma profile. For example Cascade usually has reasonably high oil levels and has a very distinctive, citrusy aroma that comes through even when the oils are lower. (Oil levels in the hops start out high near harvest time and get lower as the hops age.) East Kent Goldings, on the other hand, typically has lower oils to start with and a mellow aroma that has a hard time competing with the other beer flavors. To put this in perspective, it would be common to use 1.5 oz. (43 g) of Cascade in a five-gallon (19-L) batch, while you might need three to four oz. (85 to 113 g) of East Kent Goldings to get the same degree of hoppiness (although the aroma and effect would be different).

As for what varieties you can use, there are no rules, so feel free to experiment (you might just invent a new style!). The most popular hop for dry hopping in the United States is Cascade. But you can use any hop with decent aroma. The newer high-alpha hops are being used a lot these days, with Centennial and Columbus heading the list. Smell the hop while it’s fresh. If you can imagine that aroma in your beer, go for it! You might also experiment with mixing varieties.

Temperature also plays a role in the quality and strength of the hop aroma. Warmer temperatures extract more oils than colder temperatures — this is particularly evident with whole hops. In a fermenter a rule of thumb is to dry hop near 70 °F (21 °C).

So it’s hard to answer the question of how much to use. If you are a hophead, always use more hops than less if there is a question. Fritz Maytag, owner of Anchor Brewing Co., once said that if you’re going to err when it comes to dry hopping, always err on the high side. You want folks to know the beer’s been dry hopped and not have to search really hard for that flavor. Start out with an ounce to 1.5 oz. (43 g) in a five-gallon (19-L) batch and adjust from there.

Just remember that the hops with which you dry hop must be absolutely the freshest possible. Any off-flavors you smell in your hops will end up in your beer. So if your hops smell cheesy or like an old gym sock (both signs of oxidation), toss them — in the trash that is, not in your beer!

Issue: August 1997