Hops can be a beautiful thing. Bitter, floral, and full of life. In fact, one of my greatest-ever fresh hop experiences took place one day on a golf course in St. Paul…at the turn I bought a hot dog and a Summit EPA on draught from a newly tapped keg. I took one sip, and the hops just exploded off the beer. I promptly threw away the uneaten dog, as there was no sense in confusing my palate. I wanted to completely enjoy the freshest tasting beer I had have ever come across.  

But we’ve all heard it before… 

“Nice IPA, but it’s been on the shelf for a few months and the hops have really faded.” 

I’ve certainly noticed this phenomenon in commercial beers, as well as my own home brew, and don’t doubt that many styles such as pale ales, IPAs and some lagers really do benefit from being enjoyed as freshly as possible to get that true hop bite and wonderful bouquet. On the flipside, other styles such as barleywines can benefit from aging to let the hops mellow out and fade into the malty background over time. 

But what’s the science behind it all? How much DO hops really fade over time? Does age have more impact on aroma, or does it also affect bitterness? At what point do hops start taking a noticeable nose dive…a couple weeks? a month? longer?

To try and find some answers, I first turned to Ken Grossman, founder of Sierra Nevada and one of the pioneers of the craft beer industry in this country. Sierra Nevada’s Pale Ale is considered by most to be the protoypical hoppy American ale, a hop bomb in its day that helped define an entire category and pave the way for literally thousands of other American-style pale ales and IPAs over the past several decades. Starting in 2002, the brewery began growing nearly three acres of hops on its own grounds, primarily focused on Cascade and Chinook used exclusively in their Estate Ale series, with a more recent four acre addition in 2008 that has made room for some experimental varieties.

According to Grossman, hop degradation is a complex mix of variables, at an early stage determined by how the hop was grown and handled prior to brewing.

“We actually have been focusing on hop aroma analysis and hop chemistry for many years, and have devoted significant resources in this area,” Grossman said. “Just to name a few variables, the crop year and harvest maturity can have a great influence. If you are using dried hops – rather than fresh picked  – kilning methods and temperature will have some influence on aroma. Storage conditions after harvest will also change the aroma characteristics greatly. Some of the ‘noble’  aromas in European hops are thought to be from warm storage and oxidation directly after harvest, and some types of hops develop ‘cheesy’ off flavors if not stored cold.”

Once hops are used in the brewing process, a whole different set of complex variables come into play. The bittering and aromatic characteristics of hops come from resins in the hop flower, which are made up of alpha and beta acids. Different hop varieties have different levels of each acid, making some more desirable for bittering as the alpha acids are isomerized in the brew kettle, and others better for lending a floral nose thanks to the beta acids left behind after boiling. 

“From addition times in the kettle, dry hopping, loss of oils from different fermentation temperatures,  and fermenter design, the list of variables impacting aroma and bitterness goes on and on,” said Grossman. “But in a nutshell fresh hops are better in our opinion, if you are looking for lots of clean robust aroma.”

Tom Nielsen, Sierra Nevada’s senior research analyst focused on hop degradation, says that their research has shown that after about two and a half to three months, hop aroma in a packaged beer, derived mainly from beta acids in the hop flower, has already started to diminish significantly. It’s a sentiment backed by Patrick Langlois at Great Divide in Denver, brewers of notable hoppy beers including their Fresh Hop Pale Ale, Titan IPA, and Hercules Double IPA. “Hops tend to dissipate in three to four months, which is why that is the recommended shelf life for most of our beers.” 

According to Nielsen, agitation during shipping can be a significant contributing factor to degradation in aroma. As a beer sits on delivery trucks and eventually finds it way to your local liquor store, the beer’s aromas can be kicked up through the head space and slowly forced out of the crown liner, a process Sierra Nevada refers to as scalping. Nielsen also says oxygen will destroy hop aroma very quickly, whether naturally over time, or through the bottling process.

“We’ve found the hop aroma of a fresh beer shipped overnight from Boston compared to the same beer that just sat here  in Chico was very much reduced,” said Nielsen.  “This degradation doesn’t noticeably impact bitterness. But since aroma plays a significant role in your perception of taste, it can greatly influence your overall enjoyment of the beer.”

Gerri Kustelski, director of quality assurance at Summit Brewing in St. Paul, agrees.

“Organoleptically, there may well be discernable changes,” Kustelski said. “Bitterness can be masked by oxidation and aging, and aroma even more so.  You begin to slowly lose the aroma imparted by dry hopping fairly quickly, possibly within several weeks.  Packaging and distribution processes including shipping and temperature control can affect the flavor stability of beer and, thus, affect the perception of hop aromas and bitterness.” 

The relative levels of alpha and beta acid compounds in a packaged beer also lends perspective to how sensitive and fragile hops can be.

“Aroma compounds are typically measured in parts per billion, compared to bittering compounds which are evaluated in parts per million,” Nielsen said. “If you lose half of your aroma compounds through agitation in shipping, that’s a much more dramatic degradation compared to bitterness. When you’re talking about aging a beer for many years, like our BigFoot Barleywine, the bitterness will eventually fade and change character, but generally speaking aroma is the first component to quickly fall out.”

Once the beer does arrive at your local bottle store or watering hole, some retailers take extra steps to ensure their beer loving customers are able to enjoy the product as closely as possible to how the brewer intended it.

“We certainly do take extra steps to make sure the beer you buy is as good as it can be,” said Jason Alvey, owner of The Four Firkins in St. Louis Park. “We keep the store as cold as we can so even the beer that is not refrigerated is nice and cool. We eliminate sunlight and filter all our lights for U.V. which can of course create a chemical reaction with the hop acids and skunk the beer. But by far the one thing that has the biggest effect is product turnover. We do not have beer that sits around on our shelves for months and months, so the beer you buy from us is as fresh as it can be. Unless of course you are buying a vintage beer that has been carefully aged in one of our climate controlled cellar fridges!”

The bottom line: if you’re interested in getting that full-on, hoppy experience in both aroma and flavor, heed the advice of many hop heads out there. Fresh really is best.