How does Hop Alpha Acid work exactly?

[Microphobik]

It's my understanding that the hop's alpha acid level has to do with how bitter it is, but I am unclear how one would adjust a recipe based on differing levels of AA. I'm also not clear how adjusting the hop level based on AA would effect other aspects of the beer.

For example... Lets say a recipe calls for 1 oz of a hop that has an AA of 5%. But when I buy that same hop variety the package says that what I have has an AA of 10% (just trying to make the numbers easy). To get closer to the recipe would I cut my hops to .5 or would that then give me less of the important oils that help with preservation, and/or anything else that might be essential?

How does one adjust a recipe based on variations in hop AA?

 

[tsl346]

Convert to Homebrew Bitterness Units (HBUs)

HBUs= %AA* oz hops

so HBU= 5%AA * 1 oz = 5 HBUs
then you can calculate how many oz you need based on the %AA of the packet

5 HBUs/10%AA= 0.5 oz

 

[Microphobik]

So the HBUs are the only factor? If I have a hop that has twice as much AA than I want I should just cut the weight by half in my recipe? Aren't there other factors such as preservation, or not so much?

 

[SixStrings]

It helps to think of the alpha acid number as percentage by weight.

So for every half-ounce of 10% AA (by weight) hops you use, you're essentially distributing the same amount into the beer during the boil as you would with a full ounce of 5% AA (by weight) hops.

 

[Cyclman]

You are right, in that oxidation, age, storage temps., etc, do affect bitterness in the final product. In a macro brewery, all this is tested to "normalize" the end product. In homebrewing, this isnt' possible. Buy fresh and hope for the product to be close to the stated packaging values.

Your math is right, if the AA is double what the recipe calls for, 1/2 the product is appropriate.

On the other hand, I made a steam beer with AA much higher than the recipe, and people raved about it.

Brewing software is very helpful in making such adjustments, a great investment for $25.

 

[DrunkleJon]

Additional information about hops and bitterness. Some hops are primarily bittering hops, some are primarily flavoring, some are dual purpose. Usually hops do not vary in AA by 5-10% and some hops seem cleaner in bittering than others. The primary concern though with bittering additions is to get the IBU's up, so in that case the appropriately dubbed HBU's are the important part. As long as you stay in the same family you usually will end up with something good.

 

[Microphobik]

Thanks for all the info guys. I didn't know it was just about the IBUs. I thought there were other important aspects of the hop plant. Namely the hops effect on shelf life. My understanding was that was why the IPA was invented in the first place. But I'm taking from this that the IBUs and are essentially related to whatever that element is and so that is all I need to worry about on the preservative front. Correct me if I'm wrong.

I am in New Zealand and often see much higher AA levels on the NZ grown versions of traditional hops. All I have ever done is use the same amount as the recipe suggested thinking that there was more than just bittering/flavor/aroma to a hop plant. This has been a big lesson for me that I can't believe I didn't figure out sooner. So thanks. Especially important because I tend to like maltier beers with more mellow hop profiles. Yet my Pale Ales come out like IPAs. That will no change.

What is the low end of AA you might ever see in a traditional beer? I like malty beers and have been looking at some recipes that just called for a single addition of 1 oz of hops with just 3 or 4% AA. Is there any point where I will have an issue with preserving the beer?

 

[rajun50]

You can make beer without any hops at all. The alcohol, sanitation, and the pH (I think) preserve the beer as well.

 

[Microphobik]

You can make beer without any hops at all. The alcohol, sanitation, and the pH (I think) preserve the beer as well.

Didn't know that. Always thought there was a preservation issue. Thanks.

 

[Baileisdad]

They say hops helps preserve beer from spoiling over long periods of time. I think I read that some place. Keeps it from getting that sour stale taste or something like that. Google it I am sure you will find ur answer.