Mate dust is crucial for many reasons, but let’s get the main one out the way first.
Mate dust contributes to the flavor of the mate.If you compare the taste of Argentine yerba (low polvo content) to Brazilian chimarrão (high polvo content), the taste is night and day. One of the reasons is because chimarrão isn’t aged, but it’s also because of the amount of dust. I can’t tell you in what exact manner it affects the taste, but when it comes to Argentina versus Brazil, Brazil’s yerba has a much milder flavor.
Mate dust also affects the body of the mate.From my experience, usually the more powder a yerba has, the fuller its body and the more texture. Instead of the fluid feeling smooth and light, it feels slightly thicker and creamy. Sometimes, it can also be a bit sandy or grainy as inevitably, some dust passes through the bombilla.
Lastly, dust makes preparing the mate easier and more aesthetically pleasing.Without powder, forming a nice mountain of mate is almost impossible. You’ll experience this when you drink most Argentinian brands. But with a good amount of dust like brands from Uruguay and Paraguay, it acts as a glue when wet and holds all the leaves and stems together. Now, if there’s too much dust like Brazil’s chimarrão, that’s when it can be a problem. Preparing chimarrão is much harder than preparing any other yerba.