Kegged DIPA lost bitterness and aroma after three weeks in keg

Question

I made my first DIPA with all Citra hops.

After about a week in primary, I transferred the beer to a keg, added a little hop sock and added 1oz of Citra. Left it that way for another week and then transferred to another keg which I then force carbonated. About a week later, I started drinking the beer and it was delicious. About another two week later, I had a beer and it didn't taste at all what it tasted like when I drank it at first. Quite a bit of the bitterness and aroma disappeared.

I checked all the normal stuff - Cleaned the Tap and beer lines etc. I even at a point shook the keg to get all of the 'stuff' that fell out back in suspension again, but this only slightly helped get some of the aroma back (not sure if this was just in my mind though).

I want to make sure you understand that I don't think this was any sort of infection. There was no indication of this, no other off-flavours nothing -

Has anyone experienced this?

Possible useful information: The hops was vacuum sealed and stored in my freezer for more than a year.

Answer 1

That's not at all an usual occurrence. Bitterness will fade somewhat with time and aroma even moreso. Especially with older hops like you used.

Answer 2

If you want to read more, there's an excellent article about just this at realbeer.

In a nutshell, hop oils are volatile and degrade easily. Oxidation due to O2 in the headspace is the biggest reason, but there are others. There's no way to stop this process but you can slow it down slightly - that article recommends oxygen absorbing caps.

Answer 3

While I generally agree oxidation can be a culprit, if you followed accepted fermentation, transfer and kegging practices this should not be an issue with a young beer.

Check your carbonation. Too much carbonation can really mask aroma and flavor of otherwise very flavorful beers. Happened to me on a Blueberry Wheat I made. If its too much, disconnect the air line, and once or twice a day, pull the relief to vent the C02 coming out of the beer. Keep tasting it each day and eventually the carbonation will reduce. If you are a little worried about Oxidation after pulling the release value you could always flush the headspace with 1-2 psi of c02 after draining, but I never worry about it. I have done this 5 times or so, usually when I try to carb a keg too quickly by setting the air high then forgetting about it.

Answer 4

There is a definite flavor curve on most ales.Maybe not so much on commercial brews as homebrew.I think it's at least partially a function of gravity,with the solids(flavor?)dropping out over time.