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Very low alpha acid -- a sign of old hops?


Master Brewer
Mar 16, 2010
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I have a question about the alpha acid percentage listed for a particular hop variety at my brew supply store.  I was about to order some Hallertauer hops, but I noticed they list the alpha acid at 2.2% for leaf hops.  BeerSmith, on the other hand, gives 4.8%, and sources I've found online and in a couple of books list 4% to 5%.  I called the store, and was told this is not a typo, the alpha acid really is that low.  I've also noticed that some of their other varieties are lower in alpha acid than BeerSmith suggests, though not by as much (Fuggles 4% vs 4.5%; Northern Brewer 6.5% vs 8.5%).

Is this normal and acceptable -- just change the numbers in BeerSmith and move on?  Or is there a problem with their variety?  Perhaps it's been sitting around too long?

The AA% on the label is usually from testing as the hops are packaged.  The AA% of all hops seem to vary from harvest to harvest, and growth area to area. I have never seen a package that gave the the date of the testing so we could have some realistic idea of age.  I wish they would.

In our area, unless you buy bulk online, the hops are packaged and distributed by LD Carlson. I always check the label for the AA% as it can be different from one purchase to another and whole hops seem to always be a lower AA% than pellet for the same type.

We duplicaed the hop listing in the BeerSmith Hop database and rename it XXX Current Batch  and change that AA% to that of our current purchase. That way the original database values are retained and we have a hop selection  to pick and modify based on the current AA%. See example in attache reciped. We gave up trying to age them.

We base all recipe batch to bach hop additions on BU/GU. We determine the amount of full boil hops to achieve the BU/BU. Then we build IBU ratios for later additions. So if it takes 1.25 oz to achieve a .5 BU/GU and the IBU is 24, we might use 3/4 of the IBU to bitter, 1/8 for Flavor, and 1/8for aroma. Having an IBU target, we use the Increase or Decrease buttons for each addition till the additions IBU matches what the ratio required. This example would require 18 IBU (3/4 of 24 total IBU) at a 60 min boil, 3 IBU (1/8 of 24 total IBU) at 20 min boil, and 3 IBU (1/8 of 24 total IBU) at 7 min boil. The weight of each addition will be whatever is required to give the IBU value for that addition at that time of boil. This gives us hard quantitative numbers to use as we trim/improve our recipe. We hope this will allow us some consistency.

How do you all do it??  ???



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Thank you very much, I appreciate the information. :)

But I'm still somewhat concerned.  I know the alpha acid is variable between harvests, but these half half the usual amount.  Can that mean something is wrong with these hops?  Or is it normal for some harvests to have as low as half the expected amount?
Half is probably not typical, but it's like wine.  Some years stink.  Some of the premium vintners don't put out their wine if they don't like it.  For hops, I think it's just that drop in Alpha acid produced on vine.
Thanks, it's good to know that isn't a sign that something other than a less-than-ideal harvest has gone wrong with the hops.  I don't mind adding a bit more to compensate for the low alpha acid; I just don't want them to ruin my beer.  It's my job to mess things up around here.  ::)
As I understand it, you can only put so much stock in that AA number anyway.  That AA number isn't going to be the same from year to year obviously but it isn't going to be the same across the entire harvest either.  What they do, as I understand it, is test just a certain amount of the harvest and then average the numbers together to get the AA# placed on the package.  If you're a macro brewer this is no big deal since you are often using the entire lot that was tested so it...we...averages out.  As homebrewers however, we use so much less that the AA number on the package is really just a ballpark figure based on the average of the entire lot that was tested.  I can't remember if its the whole harvest, lbs, bushels or whatever but I can assure you, that unless you pony up to have that oz tested yourself, there is no way to know for sure, exactly what the AA acid is in that 1 oz package, regardless of what is printed on the package. 
Er... does that mean I should not use the number on the package in BeerSmith after all?
You can and probably should use it.  Its the best guess at what the AA is of the hops inside the package.  But understand that it is only an approximation and there is no guarantee that the hops inside those 1 oz packages are really the AA listed on the package. Though, my guess is they probably aren't all that far off
Dejhuty, Wildrover,

To us, you are on the topic that concerned us the most since starting to brew. Hops are the biggest variable that can make or break a brew, yet it is the one variable we, the small homebrewer, have the least control over. As Wildrover says, unless you can lab test each oz you purchase, you have nothing to go by but the AA% on the package. On top of this, there are the great debates on Utilization. Do you use Rager's formula? Or maybe Garetz's? How about Tenseth's?? on and on and so fourth.
We take Ray Daniel's advice here, (author of Designing Great Beers, a book you would enjoy) He feels that we,(beer drinkers), can only perceive a 5 IBU difference in most hops. That says that if you only hit your IBU target + or - 5 IBU, you probably will not notice a difference. On Utilization, (change in IBU vs OG per oz if hops) Ray Daniels feels Rager & Garetz are on opposite extremes and Tenseth is in the middle so that is the Utilization formula he uses. Armed with these two bits of advice, we have put together our hopping scheme.

Regardless of the brewing software, or calculator method, we use Tenseth's formula for Utilization.  We take great pains to develop our brewing practice and procedure so that we can be very consistent in how we brew. Then we do everything by numbers. Especially hopping. As we mention above, we first determine the BU/GU ratio of the recipe. See our earlier post.  Then we stick with middle alpha hops. Ones in the 6% to 10% AA range.  Most of them are hybrids of the lower IBU Noble hops so you don't give up that much in character. Also since they are higher in AA%, the variations we encounter in the AA% from season to season or whatever, are a smaller change in the total. Example a change of 2% in a 4% AA hop is a 50% change. A 2% variation in a 10% AA hop is only a 20% change. Also having a higher AA% per oz, they are more economical to use. Using our numeric ratios and basing everything on BU/GU, we can easily hit the targets within 5 IBU and hope a smarter guy than us (Ray Daniels) is right.

If we are going to duplicate someone elses recipe, we do necessarily use the hop addition weights given. We use BeerSmith and the commonly published AA% for the hop and determine the IBU of each addition and is % of total IBU. Then we make the weight changes required to hit these IBU targets with the current AA% hop.

How do you guys do it??