Hop alpha acid loss over time

Toxophilly · Mar 13, 2017

Hi all,

I came across this calculator which purports to calculate the alpha acid loss of hops over time: http://brewerslog.appspot.com/HopAlphaCalc

In my case, I have an unopened pack of Galaxy at 13.7% AA from the 2016 harvest. 2016 harvest is decent compared to some hop packets I've seen.

I gather the Australian hop harvest is in March and it's March now, so I enter 365 days old into the calculator; that it's "Sealed in barrier packaging, airtight jars [foil pack] under vacuum"; and I can't guarantee the homebrew supplier kept them refrigerated so I put in 21 degrees C as the storage temperature.

Based on this, the calculator tells me the hops now have 4.5% AA. I suspect if I were to adjust my recipe accordingly and pile in loads more hops to hit the IBU I'd end up with a horribly bitter beer - the calculator's got to be wrong :wha:

Any thoughts on this calculator, and accounting for AA loss when designing beers or following recipes?

: cheers:

dad_of_jon · Mar 13, 2017

Toxophilly said:
Hi all,

I came across this calculator which purports to calculate the alpha acid loss of hops over time: http://brewerslog.appspot.com/HopAlphaCalc

In my case, I have an unopened pack of Galaxy at 13.7% AA from the 2016 harvest. 2016 harvest is decent compared to some hop packets I've seen.

I gather the Australian hop harvest is in March and it's March now, so I enter 365 days old into the calculator; that it's "Sealed in barrier packaging, airtight jars [foil pack] under vacuum"; and I can't guarantee the homebrew supplier kept them refrigerated so I put in 21 degrees C as the storage temperature.

Based on this, the calculator tells me the hops now have 4.5% AA. I suspect if I were to adjust my recipe accordingly and pile in loads more hops to hit the IBU I'd end up with a horribly bitter beer - the calculator's got to be wrong :wha:

Any thoughts on this calculator, and accounting for AA loss when designing beers or following recipes?

:

what does stored at 5 deg c give you? if its a radically different number again then the variability of storage could be an issue with an accurate AA%. In that case use fresher northern hemisphere hops for bittering only?

I'd also trying a different calculation to see if the figures plugged in tally!

Toxophilly · Mar 13, 2017

dad_of_jon said:
what does stored at 5 deg c give you?

Stored at 5 degrees gives 8%, so better but still a significant loss.

Not a bad idea on using northern hemisphere hops for bittering. I'm yet to be convinced on whether using different hop strains for bittering imparts different flavour characteristics, or if it's all just bitterness... :hmm:

Slid · Mar 14, 2017

My guess is that bittering will linger mush longer than the elements that contribute more to flavour / aroma.

I think you will be OK if you use your Galaxy as if it were pretty much current. The main detriment will probably come during the time and process between picking and sealing the vacuum pack.

As hops are only harvested once a year, it makes no sense to me that they are rubbish inside 11 months.

BlackIsland · Mar 14, 2017

I was entering three new packages of hops into my brewing software yesterday, and the numbers for the stability index always leave me scratching my head. The HSI (measure degradation of alpha acids over 6 months) is based on storing them at 20C. Storing them colder extends their life. Keeping them away from oxygen and light does as well. And pellet hops are less susceptible to degradation.

Since I'm not a commercial brewer, I don't have to be as concerned with the HSI, and since I vacuum seal my hops between brewing sessions and keep them below 0C, I hope I'm getting more life out of my hops. I buy most of my hops from a grower in my state, so they typically only spend 2 days warmed up after processing, as the grower freezes them in mylar bags. The only hops from them I have any concerns over are the ones they get from Oz/NZ, the UK, and Germany/CZ, as I have no clue how they were transported here. I just brew, taste, and add more if I think they're not potent enough.

FWIW, Brad Smith over at BeerSmith has a nice list of individual hops, and you can see their HSI by clicking on the hop variety. http://beersmith.com/hop-list/

Leon103 · Mar 14, 2017

Beersmith as a calculator. Try that to see if it's the same.

chthon · Mar 14, 2017

Today I ran also against this calculator. I brewed a pale ale which should have had an IBU of 35. But it tastes much weaker. Today I checked my hops and they are from 2015, so that probably means end of Sep 2015. They are Kent Goldings at original 5.1%, and Fuggles original at 6%. Calculating this (sealed tight and frozen, but not completely free of oxygen) I get new figures of 3.1% and 3.6% respectively. These figures seem reasonable, in both cases I would need to add 60% more hops.