I've been thinking a lot about the hydrophilic nature of coffee. I'm sure that research has been done, but I cannot (so far) find anything that evaluates various different types of coffee to determine if there is variance in how hydrophilic each is, how great the differences are and what patterns emerge.
I would hypothesize (purely from experience) that (when it comes to Arabica beans) high-grown washed coffees are the least hydrophilic, semi-washed (or pulped naturals) are more hydrophilic, naturals are even more hydrophilic and aged (or monsooned) coffees are the most hydrophilic.
The hydrophilic nature of each type of coffee, each method of coffee processing and perhaps even the varietals and origins is actually quite critical. It has huge implications when it comes to behavior in an espresso machine; it will affect optimal dose and thus technique and even brew temp and pressure; and as a result will dramatically affect blending decisions.
I'm very curious about this and really want to understand more.