The blend came apart

In a spice blend, segregation is a flavor problem. In a supplement it is a potency problem, which makes it the most serious mechanical failure in this property.

Why this is a potency failure

A separated blend means the top of the tub and the bottom have different compositions. A customer scooping accurately still receives the wrong dose, and the Supplement Facts panel, which is a quantitative claim, is untrue for most of the tub.

Non-uniform blends produce varying nutritional content per scoop, and nothing about the product looks wrong while that is happening.

What drives it

Segregation occurs whenever particles differ in size, density, shape or surface properties and are then allowed to move relative to each other.

Two mechanisms do most of it. Percolation: smaller particles filter down through the gaps between larger ones, which is why fines end at the bottom. Elutriation: denser particles settle and lighter ones ride up.

Supplement blends are unusually exposed because their components are deliberately unlike: a bulk protein, a fine flavor system, a very dense mineral, a high-intensity sweetener at a fraction of a percent.

Where it happens

Everywhere the blend moves after mixing. Discharging the blender, transferring to a hopper, filling, and then hours of vibration in transit.

A tub that was uniform when filled can arrive stratified, which is why a sample taken at filling does not settle the question on its own.

Designing against it

Narrow the particle size range across components before mixing. Powders of similar size and density blend more uniformly and are less likely to separate, and choosing closer grades does more than any amount of extra blending.

Pre-dilute the very small components into a carrier rather than adding them neat.

And minimize handling: fill close to the blender, avoid free-fall into deep containers, and do not store finished blend in bulk for weeks before packing it.

References