I coarsely chop all my whole hops to improve the utilization and reduce the wort absorption. I use a cheap food processor from Walmart just for hops.
I had though about doing this before but was worried about leaving too much of the sticky resin behind in the food processor. Is this not a problem?
And how much does it increase utilization, anyway? It may be one of those things that seems like a good idea, but in reality doesn't make enough difference to be worth the effort. Has anyone ever seen a study about how much increase you get? And if you don't know, how do you accurately calculate your hop additions?
How much does it improve the utilization is difficult to quantify. In late additions, the chopped-whole hops perform similar to pellets. The hop resins are almost instantly available to the boil. I find that late in the boil this technique dramatically improves whole-hop performance.
The only person that has done a study about using a food processor to chop whole hops is me as far as I know. However, it is simple logic that by breaking the hop cone structure exposes the luplin that would otherwise be somewhat hidden inside the hop cone.
By coarsely chopping the hops, and leaving the majority of the hop petals intact retains one of the qualities that I prefer in whole hops, which is the filtering effect on the false bottom of my kettle and result is much less wort absorption in regular whole hops.
I accurately calculate my hop utilization like any other brewer. I carefully weigh them and use brewing experience to do the rest.