this isnt exactly a revelation, but having just read a thread on another forum where a guy has bought a very light roasted bean that he is trying to use for espresso and cant work out why it isnt working
there is currently a trend toward lighter roasts, and whilst i would like to think we are not leading it and no where near the front either, we are roasting much much lighter than we used to
we could argue indefinitely about light roasts and espresso, but one thing is for sure – you are going to need a very capable grinder if you plan on making espresso with some of the super light roasts that are now on offer – its like they have barely been breathed upon by the roaster.
for a recent roast that i aquired the Compak R120 needed to be cranked right past the ‘espresso’ band on the grind adjuster and well through the ‘fine’ band too, getting on towards the start of the ‘turkish’ band. this is a very graphic indication that you are dealing with a bean that has probably barely seen first crack. the cells in the bean have not been busted open by the water vapour pressure built up in the bean during the roasting process, and as a result basically no oil can escape the cell
if no oil is able to escape from the cells a very dry grind is the result, obviously, and that has to be compensated for by grinding much more finely
on a ridiculously over the top grinder like the Compak R120 this isnt an issue as you have so much ‘top end’ available to you, a bit like what it must feel like for the driver of a Bugatti Veyron to face the challenge of the boy racers – you simply twitch your big toe on the accelerator and you are gone. but on the kind of grinders that are more commonly found in the home i honestly think most people are going to find it hard work
the message is simple – if you buy a super light roast for espresso be aware that you will be asking a lot more of your grinder, and in some cases it will be unable to deliver, especially if your burrs have done a lot of work