Many personal blenders include a separate flat blade for dry ingredients, and it is among the least used accessories in most kitchens. It handles several jobs that would otherwise need a dedicated appliance.
Why a Different Blade
Wet blending relies on liquid circulating ingredients back into the blades. Dry grinding has no liquid, so the blade geometry has to throw material outward and back down mechanically.
A cross blade designed for smoothies used on dry ingredients produces uneven results and works the motor harder. Where a flat grinding blade is supplied, it is worth using.
Coffee, With a Caveat
A blade grinder chops rather than grinds, which produces an uneven particle size: some powder, some large fragments.
For a cafetière or a filter that tolerates variation, this is perfectly acceptable and considerably better than pre-ground coffee that has been sitting for months. For espresso, which needs a consistent fine grind, it is not sufficient and a burr grinder is the tool.
Pulsing in short bursts and shaking between them evens the result out noticeably. Sets that include a dedicated flat blade, of the kind at magic-bullet.net, are aimed at exactly this sort of task.
What Grinds Well
- Coffee beans, for a coarse to medium grind
- Whole spices: peppercorns, coriander, cumin, fennel
- Oats, into a rough flour for baking
- Nuts, to a meal rather than a butter
- Dried breadcrumbs from stale bread
- Hard sugar into a finer texture
Spices
Whole spices ground fresh are dramatically better than pre-ground, which loses potency within months. This is arguably the best use of a grinding blade.
Toasting whole spices in a dry pan before grinding improves them further, and letting them cool first prevents them clumping.
The Residual Flavour Problem
Spices and coffee leave flavour in the cup and gasket that transfers to whatever comes next. Cumin in a smoothie is memorable for the wrong reasons.
Grinding a small quantity of dry rice or bread afterwards absorbs a good deal of residue. Beyond that, washing the seal separately is what actually clears it.
Do Not Overload
Dry grinding works best with a small quantity, roughly a third of the cup at most. More than that and the material at the top never reaches the blades.
Short pulses with a shake between them produces a far more even result than running continuously, and it is easier on the motor.
What Not to Grind
Anything very hard, such as whole nutmeg or ice, in a machine not rated for it. Also anything that becomes a paste, since nut butters need a different approach and a wet blade.