IBU Distribution

[mroberts1204]

I know there is a term used to describe getting most of the IBUs in an IPA from late hop additions (primarily flavor/aroma). I believe this is a technique AleSmith uses for their IPA. Anyway...how should the IBUs be distributed? I know it takes way more hops to achieve an acceptable level of bitterness if adding most later in the boil (30 minutes and later). Some recipes I look at get 80% of the IBUs from bittering additions while some are much lower. Has anyone looked into this?

For instance...how would getting 100% of the IBUs from additions 30 minutes or later affect the bitterness and hop flavor of the final beer?

 

[weirdboy]

The term you are looking for is Hop Bursting. There's been a ton of stuff about it, but a good place to start is this article on MrMalty.

 

[mroberts1204]

Hopbursting!! Thats the one!! AleSmith claims:

Critical factors appear to be the freshness and low cohumulone levels of the hops, softened water (especially the carbonate/bicarbonate value), and original gravities in excess of 1.055 S.G. (13.57 Plato)

Now the low cohumulone thing is what interests me since some of the popular flavor/aroma hops such as Cascade have rather high cohumulone levels whereas the 'clean' bittering hops like Magnum and Warrior have lower cohumulone levels. Later in the article Peter Zein goes on to say:

The hops that have worked best for our late-hopping include Cascade, Amarillo, Tomahawk, Simcoe, Chinook, and a newer variety, Palisades. Tomahawk and Simcoe have relatively high alpha acid values and somewhat low cohumulone values and are best used in lesser percentages than the other hops mentioned.

This confuses me. Can anybody crack an egg of knowledge and elaborate on this?