Same hop variety, different alpha acid content

[liammiller]

I am brewing a hefeweizen and have looked at sourcing my halletau mittelfruh from two different places. I can buy hops from my LHBS that have 2.8% AA or I can buy them online that have 4.5% AA.

I understand that I can alter the amount used to achieve the 10 IBU that I want depending which I buy but I am not sure how this will affect the flavour and aroma. I realise that hop character is not that important for this style but I am curious how alpha acid content relates to flavour and aroma.

 

[terrym]

Here's my twopennorth....
Your hop is an aroma hop, not a bittering hop, according to this,
Hops Varieties for Brewing Beer Guide | Where legends are made
and other chemicals are more important to the hop than alpha acids, in as noted in this extract
Hallertauer Mittelfrüh is an aroma hops variety with an alpha acid rating of 3.5%-5.5%. It is closely associated with the German Style Lagers, it is part of the Hallertauer family of hops. Hallertauer Mittelfrüh has made its mark on the world of brewing, and is known for its slightly spicy aroma and character. It has moderately high myrcene, and caryophyllene oil, which help contribute to the aroma profile in the finished brew.
So although you know the %AA of the different years you have no idea of the relative content of chemicals that provide flavour and aroma (latter as above).
If you go for the low %AA hop (since you are intending to use it for bittering) you may end up with more flavour because you would have to use more to achieve the same IBU.
And aroma will be maximised if you dry hop.