Re-grinding Coffee - Just Don't!
Had an experience today which, if you are a coffee roaster, tends to send shivers down your spine. We had a call from a customer who was experiencing problems with their coffee grinder. For some reason the coffee was coming out extremely coarse.
When I got on site I found to my horror a coffee hopper full of a mixture of bits of coffee beans and coarsely ground coffee. When I asked what had happened the member of staff said that to try and reduce the size of the grounds they had decided to re-grind the coffee. Noooooooooooooooooooooooooooooooooooooooooooooooooo!
Re-grinding coffee that has not been correctly ground in the first place is an absolute no no. To get a bit technical, the spread of the particle sizes will be so great as to make it impossible to get any consistency of flow of liquid through the coffee. On top of that all that re-grinding will result in so much heat getting into the coffee that it will materially affect the taste of the coffee in a very unpleasant and burnt way. Finally you'll end up jamming the blades, the hopper entry point and restricting the flow of beans. Not bad!
If you find yourself in this unfortunate position there is nothing to do but throw away the incorrectly ground coffee and then gradually reset the grinding blades. As a rule of thumb the coffee needs to have the consistency of fine sand to produce anything like a decent espresso.
If you do find yourself trying to unravel the above scenario, ensure that the hopper gets a good wash and is thoroughly dry and that the entry point into the grinding discs is also clear.