[HoosierBrew]

Luckily, retailers stamp the harvest year on the package when you buy in bulk. As for the LHBS and suppliers that just weigh hops from bulk containers oz by oz, it's probably not in their best interest to give too much detail. Might be this year's crop, very well might not be.

[nathan74]

Luckily, retailers stamp the harvest year on the package when you buy in bulk. As for the LHBS and suppliers that just weigh hops from bulk containers oz by oz, it's probably not in their best interest to give too much detail. Might be this year's crop, very well might not be.

And THATS the real answer!


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[denny]

I've posted elsewhere that I'm working for a while in the lab at BSG (Brewers Supply Group) testing hops for alpha & beta acids, as well as HSI: the Hop Storage Index.

I am frankly surprised at the degradation of alpha acids in hops.  In the 3 months since harvest, the hops I am testing have dropped 1-2 % points in alpha from the harvest alpha.  I'm not experienced enough to know if that will continue at a steady decline or not.  I do know that the variety also influences the rate of decline.

What I am wondering is if we homebrewers are not taking this into account as much as we should - if at all.  All the hops in my freezer are 2014 hops.  They have an alpha acid % listed on the package but I'm not sure how to account for the decline, and they never list the HSI.  It seems to me this would be an important thing to factor in.  Any thoughts?  Do any of you factor in the age of the hops for calculating IBUs?

I use a rough ROT to adjust hop amounts for age.  A SWAG is good enough for me, and the results bear that out.

[chinaski]

I'm guessing that if HSI declines in an exponential fashion, then perhaps a large portion of the decline has already happened when the hops get to us.  Nevermind that the %AA on the package represents some statistical average from whatever lot of hops the package was taken from.  And nevermind any error in the formulas used to calculate isomerization in the boil.  In other words, there are lots of sources of error in the IBU numbers that show up on the recipe so I wouldn't sweat it too much.

I brew with homegrown hops using my best (researched) guess of %AA and it works.

[yso191]

I'm guessing that if HSI declines in an exponential fashion, then perhaps a large portion of the decline has already happened when the hops get to us.  Nevermind that the %AA on the package represents some statistical average from whatever lot of hops the package was taken from.  And nevermind any error in the formulas used to calculate isomerization in the boil.  In other words, there are lots of sources of error in the IBU numbers that show up on the recipe so I wouldn't sweat it too much.

I brew with homegrown hops using my best (researched) guess of %AA and it works.

I'm actually pretty confident in the number that goes on the package.  Here is why:  The second stage in the pelletizing process is mixing the hop particles in very large drums in order to homogenize.  Also most of the time hops are pelletized from a single lot, not blended.  Blending is done when a large brewer requests it.  Then each run is sampled throughout the run.  The lab gets small ~3 ounce packages of these samples.  We test each sample twice.  The two need to be within 3% of each other or the result gets tossed.  Then, it is true, all of the samples for the run get averaged, but the standard deviation in AA between samples in a given run vary only by ~.02%.

That is not much of a difference.  However losing 1-2 percentage points in 3 months off of a 15.0% bittering hop (i.e. CTZ) is a significant drop.  If the rate of decline is constant, by July/August 2016 the 15.0% hop is now 7-11%!

I know that not all varieties lose AA at the same rate, and other factors come in to play but...

I did look at the MoreBeer link.  To be honest it went over my head, but I am considering making a spreadsheet with all the variables factored in, in order to make a reasonable prediction of AA losses.

[chinaski]

I'm actually pretty confident in the number that goes on the package.  Here is why:  The second stage in the pelletizing process is mixing the hop particles in very large drums in order to homogenize.  Also most of the time hops are pelletized from a single lot, not blended.  Blending is done when a large brewer requests it.  Then each run is sampled throughout the run.  The lab gets small ~3 ounce packages of these samples.  We test each sample twice.  The two need to be within 3% of each other or the result gets tossed.  Then, it is true, all of the samples for the run get averaged, but the standard deviation in AA between samples in a given run vary only by ~.02%.

Wow!  That's a lot more QA than I had assumed.  Good to know that you guys are doing so much to keep track of the acid content.  Thanks for that info!