gritty texture - drum roasting

[markchile]

I have recently changed from convection oven roasting to drum roasting.  The drum has 10KG capacity and airflow control.  I am using the same origin of beans.  In my first test roasts in the drum roaster, I am noticing that the beans have a gritty/powder texture that I never perceived when I roasted in a convection oven.   I made a test batch of chocolate with the drum-roasted beans and I also noticed this slightly gritty/powder texture in the chocolate.  Is it common that drum roasted beans have a different texture than convection oven roasted beans?   Or is there something that I need/can to do differently with my drum roast to reduce this texture? 

Let me know if there is any more information that I can provide to help guide your response.    Thanks in advance.   Mark

[Brad]

Mark.

The roasting technique has nothing to do with the texture of your finished chocolate. Grittiness is a result of not refining long enough. If you change your roasting profile then you may also need to change the amount of time you grind the beans.

Brad

[Sebastian]

Assuming you're whole bean roasting, if you're not removing enough moisture for your shell to separate from the nib, that'll impact you winnowing, resulting in more shell carrying through. If you're getting shell in your nib at excess levels, you'll get grit. Have you measured your shell in nib results? Generally speaking anything over 1.75% is going to be quite bad - but you'll want it as low as possible. No idea if that's what's causing your specific issue or not, but it could be.