Flow, and why it is a dosing problem

How a powder flows looks like a handling convenience. It is actually one of the inputs to whether a serving is the right size.

Flow is not tidiness

A free-flowing powder fills a scoop consistently, empties a hopper evenly and packs to a predictable density. A cohesive powder bridges, rat-holes, packs unevenly and delivers a different mass every time.

Since the scoop is the dose, flow is a dosing variable rather than a nuisance.

What makes a powder flow badly

Fineness. Very fine particles have more surface area relative to mass, so cohesive forces dominate and they stick to each other and to everything else.

Moisture. Hygroscopic powders take up water and the wetting of the solids degrades flow directly, along with dosing accuracy and hardness. This is the commonest cause of a product that flowed on your bench and does not in the customer's kitchen.

Shape. Irregular or plate-like particles interlock. Spherical ones do not.

Static. Generated during blending and transfer, and it makes fine powder cling to everything including the inside of a scoop.

Where bad flow shows up

In filling, as inconsistent weights through a run. In the tub, as a powder that has consolidated into a mass that scoops unpredictably. In the scoop, as the difference between a leveled and a compacted measure. And in a hopper, as bridging that stops a fill line.

Improving it

A flow agent at a fraction of a percent, which is what silicon dioxide and similar excipients are for. They coat particles, interrupt cohesion and are one of the highest-leverage small additions available.

Controlling moisture, which is the same discipline that protects stability: dry blending conditions, sealed storage, a barrier closure.

And narrowing the particle size range across components, which helps flow and segregation at the same time.

References