Where does hop flavor/aroma go?

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musick

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Talking about botttles here.

Its common knowledge that the hop profile fades when comparing a freshly bottled beer to one that has undergone extended aging. Assuming a tight seal between cap and bottle, proper storage temp and away from light sources, where does it go? Seems like after pressure develops, flavors/aroma would be under pressure and not escape (in a meaningful way) into the minimal headspace in a bottle, nor would the yeast be as active, as to act as a vector for hop degradation. Appears to be the case when a beer is either filtered or unfiltered.

But we all know it does happen.

Can anyone provide any articles/ideas of what happens to the hop profile? Guesses are fine, but factual info would be greatly appreciated.

Thanks in advance and Na Zdrowie! :rockin:
 
I'm under the impression that it doesn't really go anywhere.

Matter cannot be created or destroyed, so it isn't just disappearing. It is still in the bottle somewhere, but my thinking is that it has either structurally isomerized (changed it's structure into something that you can't smell or taste) or that it has just broken down over time. For some reason the second explanation seems more plausible to me.

It makes sense, because if you leave hops out of the freezer or out of the vacuum packaging then they lose their flavor, so when they are in the bottle environment the same thing happens. It is probably just a product of reactions occurring at room temperature. Someone should bottle half a bottle or so of beer, then freeze it, and compare it to a bottle that was unfrozen and see the results there.
 
For some reason the second explanation seems more plausible to me.....Someone should bottle half a bottle or so of beer, then freeze it, and compare it to a bottle that was unfrozen and see the results there.

Thanks for the replies!

While I do agree, the pressure inside the bottle would lead me to theorize that a minimal drop in profile would be plausible, but anyone who has compared written notes on a 4 week old IPA @ 8% to the same one at 8 months old would (?) agree (at least based on my experiences) that there is a HUGE difference, not a slight one.

Maybe the alcohol breaks it down into another form....but where does it go? :confused:

Somewhat along those lines, I aged a few bottles from the same batch under two conditions - some were stored immediately after bottling in my fridge, the others in a dark, cool closet.

There was a difference between the 2 conditions when tasting, but I attribute that to the slower carbonation rate between the cold and room temp conditions.

Sorry for the semi-rant; just getting back into the art after a 12 month hiatus and have all sorts of questions.

Prost!
 
this phenomenon used to bother me until i realized that some things in life just can't be changed. from that point on, i've been determined to enjoy all of my hoppy beers as quickly as possible, and have been pretty successful. something to think about. i would like to know the mechanism responsible though.
 
I'm no chemist, but I assume hop flavor-active compounds are huge, complex, delicate molecules that simply get busted up with time, temperature, light and oxygen. And maybe microorganisms.
 
hopscopy.jpg
 
Isn't it crazy that I can't stand Hannah Montana, yet I think iCarly is one of the best shows on tv right now? Weird.

A think that the molecules that make up hop aroma do break down and become something else that is less noticeable.
 
Machinelf: I'm standing in my office, giving you a slow clap right now.

Genius!

Here I stand in my office, bowing with gratitude. :mug:

Regarding the point of the thread, I've always heard that the essential oils that are responsible for aroma/flavor are volatile, so I would assume that they simply break down over time.
 
It's not much, but this article indicates that the aroma loss comes at least partially from beta acid decay:
http://captainsbeerblog.com/2010/03/23/fading-hops/
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.
...
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.”

If you want the mechanism of decay:
http://www.realbeer.com/hops/aroma.html

"The major mechanism for the loss of hop aroma compounds from beer appears to be chemical degradation . The most likely pathways for degradation of terpenoid and sesquiterpenoid compounds are reaction with oxygen in the headspace of the bottle and acid hydrolysis."
 
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