IBUs of non hop additions

[Joewalla88]

I want to do an elderflower pale. I'm trying to adjust my hop additions to work with the elderflower additions, and am wondering what kind of bittering I can expect from the elderflowers. I know that there's probably no calculation for that anywhere, and they probably aren't contributing to the actual IBUs, but seems like they could definately add some perceived bitterness. Does anyone have any ideas, or maybe advice on the best way to use elder flowers? I'm planning to do a pale or blonde ale with hallertau blanc and elderflowers as the late additions and possibly a dry hop with them as well.

 

[dmtaylor]

I haven't used elderflowers myself but tasted them in others' beers. I think they add more tartness than bitterness.