Does the %AA in hops decrease over time?

[Limited Repertoire]

I was wondering how to use hops that are from 2011 or 2012. Is there some rule of thumb about the %AA going down over time? I notice on BeerSmith 2 has a "Hop Storage Index" on the hop window when you add it to the recipe. That seems to say that it can go down by a significant percentage (40%!) every 6 months. If so, then just knowing the year won't be enough information.

Jeff.

[Ozwald]

I was wondering how to use hops that are from 2011 or 2012. Is there some rule of thumb about the %AA going down over time? I notice on BeerSmith 2 has a "Hop Storage Index" on the hop window when you add it to the recipe. That seems to say that it can go down by a significant percentage (40%!) every 6 months. If so, then just knowing the year won't be enough information.

Jeff.

ProMash has that too. In my experience, it's always wrong. I tried using the scale with hops from 07 & 08 on beers I brewed this year. They degrade somewhat, but I would've been a hell of a lot closer using the data on the package, or telling the calculator they were stored perfectly in nitro/mylar for a few months instead of the actual year & being stored in PBW jars.

Knowing the year is enough, as well. It's not like tomatoes or strawberries, etc. They're predictably harvested at the same time every year within a few weeks & pelletized very shortly after.

After messing with it a few times, I don't bother anymore. Use the numbers provided & you'll be close enough.

[dmtaylor]

+1. I find that alpha acid degrades, but not as quick as the references say. I always figure for 2-year old hops, they probably lose a maximum of 30-40% alpha if kept in refrigeration, so I use them that way and the bitterness usually comes out very close to what I expect. If frozen they should lose even less, maybe only 20% but that's just a swag. Really... it's all just a swag, ain't it? With an educated guess, you can usually get close enough in my experience.

[Ironman]

http://morebeer.com/brewingtechniques/library/backissues/issue2.1/garetz.html

If you're storing your hops at 68F...

[biertourist]

Myrcene levels also drop off quickly under aging (including/ especially in finished beers). (Hops with lower Myrcene levels are more "flavor stable" over time.)
Beta acid levels can increase upon aging and are generally more bitter so the perceived bitterness levels won't drop off as quickly as the %AA decline would indicate.


Adam

[Ozwald]

Beta acid levels can increase upon aging

Correct me if I'm wrong (& please provide a source - not cause I doubt, but for personal education), but I was under the impression that the acid levels can not increase, only degrade with time. Beta being more stable than alpha just becomes more pronounced since it's not degrading at the same rates as everything else.

I.E. you start with 20 'units' of both alpha & beta, over X time when alpha hits 5 'units' the beta would still be, say for example, 18 'units'. Not increasing but giving the impression that it's increasing by comparison. Of course all the other compounds would be degrading at their own rates, but more similarly to the alpha scale than the beta scale thus enforcing the impression.

[spiderwrangler]

Beta acid levels can increase upon aging

Correct me if I'm wrong (& please provide a source - not cause I doubt, but for personal education), but I was under the impression that the acid levels can not increase, only degrade with time. Beta being more stable than alpha just becomes more pronounced since it's not degrading at the same rates as everything else.

I.E. you start with 20 'units' of both alpha & beta, over X time when alpha hits 5 'units' the beta would still be, say for example, 18 'units'. Not increasing but giving the impression that it's increasing by comparison. Of course all the other compounds would be degrading at their own rates, but more similarly to the alpha scale than the beta scale thus enforcing the impression.

It isn't the amount of beta that changes, but the perception of bitterness as they change over time. To use your example of 20 units... if you start with 20 units of beta, 1/20th may contribute to bitterness, while with aging, more and more of those beta units get oxidized, contributing to bitterness... so in time, 11/20ths of the original beta may be perceived as 'bitter'. You are correct in that levels won't increase in terms of overall beta, but the amount of 'bitter beta' will.

http://byo.com/gift-ideas/item/848-hop-chemistry-homebrew-science

[Ozwald]

Beta acid levels can increase upon aging

Correct me if I'm wrong (& please provide a source - not cause I doubt, but for personal education), but I was under the impression that the acid levels can not increase, only degrade with time. Beta being more stable than alpha just becomes more pronounced since it's not degrading at the same rates as everything else.

I.E. you start with 20 'units' of both alpha & beta, over X time when alpha hits 5 'units' the beta would still be, say for example, 18 'units'. Not increasing but giving the impression that it's increasing by comparison. Of course all the other compounds would be degrading at their own rates, but more similarly to the alpha scale than the beta scale thus enforcing the impression.

It isn't the amount of beta that changes, but the perception of bitterness as they change over time. To use your example of 20 units... if you start with 20 units of beta, 1/20th may contribute to bitterness, while with aging, more and more of those beta units get oxidized, contributing to bitterness... so in time, 11/20ths of the original beta may be perceived as 'bitter'. You are correct in that levels won't increase in terms of overall beta, but the amount of 'bitter beta' will.

http://byo.com/gift-ideas/item/848-hop-chemistry-homebrew-science

Good info, thanks. I just found a snippet of Palmer talking about the same thing on the Math show talking about the oxidation doing it. It was just a random show that sync'd up & what good timing. I forgot how incredibly awesome that show was as well.