Blending

Blending is the step that decides whether the label claim is true for every serving rather than on average.

What a blender is doing

Distributing components so that any sample drawn from anywhere in the batch has the same composition as any other. The measure is the variation between samples, and in this category that variation is directly a variation in dose.

It is fighting physics the whole time: components differing in size, density, shape or surface properties want to separate, and mixing is the only thing stopping them.

There is an optimum time

Longer is not better. Every mix has an optimum, and beyond it the extra energy starts working against you: it generates fines, widens the particle size distribution, and a wider distribution is precisely what causes segregation afterwards.

So over-blending makes a blend that is uniform in the mixer and separates faster in the tub.

Establish the time by sampling rather than by feel, and write it into the process. It does not scale linearly with batch size, so it must be re-established when the batch changes.

Order of addition

Small components pre-blended into a carrier first, then combined with the bulk. Never a gram added neat to a kilogram.

Where components differ sharply in particle size, add the finer material into the coarser rather than the reverse, and avoid free-fall from height, which segregates as it falls.

Equipment at small scale

A tumbling or V-blender is the right tool because it mixes by repeated folding rather than by shear. A ribbon blender works and is harsher on friable material.

What does not work is a bowl and a paddle, which produces a mixture that looks uniform and is not, and a food processor, which grinds while it mixes and creates the fines that will segregate later.

References