The smallest particles in coffee grind are called “fines”. First fines was said to attribute bitterness and bad flavors to the coffee. Now fines are considered important to make coffee taste great.
How can fines end up giving opposite taste impressions ?
I have long suspected it had to do with how the fines were situated in the grind: The fines can either stick to larger particles – or to other fines.
Each result in a different taste: when fines are attached to bigger particles they act as part of the large particle in the extraction and do not over-extract as when they are separate where fines only stick to other fines.
Lately I have done a bunch of experiments on this Read more here.