Can AA Content vary in a hop type

[gunner]

I am asking this question as im going to brew 100% satisfaction,but i am confused over the stated IBU content with the recipe.

The recipe calls for 4.5kg PM,75g of 4% AA goldings 90mins, 15g goldings 15mins,with an IBU of 24.When i put the details into beer engine it gives me IBU 79,based 5.7 %AA.Even if i lower the AA content to 4% on beer engine it still comes out as 37 IBU.

But to confuse the situation i have goldings that have 6.8%AA,and fuggles which are 3.8%AA but are quoted in beer engine and BYO as 4.9%AA.

So does/can AA content vary in one/any particular hope type,if so can you stipulate what AA content your after when ordering.

Graham.

[Eadweard]

As hops are a natural product the amount of alpha acids in each crop will always vary, so calculations need to be made and the amount added to a brew adjusted.

[gunner]

So if my current goldings are 6.8% i need to reduce the amount added to achieve the stated IBU of the recipe?

Would you adjust just the 1st additions or does both additions need adjusting. To achieve a 24 IBU for this recipe you need to reduce the 1st additions to 24g and leave the 2nd addition at 15g,that seems a hell of drop in total grams from original recipe,as i thought the recipe was based on large hop additions.

[boingy]

Assuming you are doing a 5 gallon (23 litre), which would seem likely given the quantity of malt, then I suspect the original recipe contains a typo. Maybe they meant 25g rather than 75g.

As far as adjusting the hops for differing AA's then you can just scale all the bittering hops up or down accordingly. The 15 minutes additions do not contribute very much bitterness so you can leave them. I tend to juggle the hops around so I end up using a round quantity just to keep my inventory sensible. You'll often find me chucking a few grams in as the wort is cooling just to use up those odd bits of hops and to boost the aroma. Just be sure to run the numbers through Beer Engine or similar to check the IBU.

[gunner]

Hi boingy,i thought the firtst hop addition was a typo,but others in this topic,have given variations of the recipe with large hop additions.

If i only add 1st addition 24g of goldings @6.8%AA as per beer engine,would this still achieve what a larger addition at a lower AA content would in the other recipes.

[gunner]

would help if you adjusted the brew length in beer engine

[boingy]

would help if you adjusted the brew length in beer engine

Heheh. You're not the only one to do that. Did you notice an unusual OG too?