# Why powder clumps: the physics behind a perfect shake

> Whether a powder dissolves is decided in the first seconds after it meets water. What food technology knows about wetting, shear forces and clump formation - and how the WOO® Shaker Schwarz applies it.

A shake that clumps is more than unpleasant to drink - it shows that a physical process went wrong. Whether a powder dissolves completely is decided in the first seconds after it meets water. Food technology has described this process precisely.

## Four steps that determine solubility

Forny, Marabi and Palzer (2011) describe the reconstitution of a water-soluble powder as a sequence of four sub-processes: **wetting** of the particle surface, **sinking** into the water, **dispersion** of the agglomerates and finally the actual **dissolution**. Any step can be limiting - in practice it almost always fails at the first.

Clumps form when the outer particles of a heap of powder immediately take up water and build a gel-like layer. Fang and colleagues (2008) showed that powders with identical composition can differ several-fold in dissolution time purely because of particle size and surface structure.

## Why protein behaves differently from carbohydrate

Maltodextrin or glucose dissolve quickly because they are strongly hydrophilic. Protein powder is more complicated: its particle surface often carries free fat that hinders wetting. Gaiani and colleagues (2007) demonstrated that storage at elevated humidity changes the surface composition of dairy powders and measurably worsens wettability. An open pouch is therefore not a cosmetic but a technical problem.

Then there is the dependence on pH and temperature. Pelegrine and Gasparetto (2005) showed that close to the isoelectric point - for whey proteins in the mildly acidic range - solubility is minimal, because the net charge cancels out and the proteins aggregate. Heat-treated protein also dissolves less well. This explains why the same shake made with water, with juice or with hot milk gives three different results.

## What shaking actually does

Mixing means putting energy in. The shear forces created while shaking tear agglomerates apart and bring fresh water to dry surfaces. Three things matter: the **order** - liquid first, powder second, because dry powder on the bottom cakes immediately; the **headspace** - a container filled to the brim creates no turbulence; and the **time** - roughly 20 to 30 seconds of vigorous shaking, then one to two minutes of rest.

## How the WOO® Shaker Schwarz puts this into practice

The **[WOO® Shaker Schwarz](/en/shop/woo-shaker-black)** holds 700 ml and has an integrated sieve. The sieve acts as a static mixing element: it forces the liquid through a constriction with every movement and generates exactly the shear forces that break agglomerates apart. The 700 ml leave enough headspace for a 300 to 500 ml serving - a container mixes better when it is only two thirds full.

The screw closure adds to that: anyone who pre-doses dry powder and adds water only at the training venue needs a lid that stays tight. The dark wall of the WOO® Shaker Schwarz is more forgiving with strongly coloured powders such as cocoa - which does not replace thorough cleaning.

## Frequently asked questions

**Water first or powder first?**
Always the liquid first. If powder lands on a dry bottom and liquid is poured on top, the hard-to-dissolve gel layer forms immediately.

**Does powder dissolve less well in cold water?**
As a rule yes, solubility rises with temperature. Very hot water is still not the answer for protein, because heat promotes denaturation and aggregation.

**Why does foam stay in the shake?**
Proteins are surface-active and stabilise air bubbles. Shake briefly and deliberately, then let it stand for a moment - the foam collapses on its own.

## Sources

Forny L, Marabi A & Palzer S (2011), Powder Technology - Wetting, disintegration and dissolution of agglomerated water soluble powders.
Fang Y, Selomulya C & Chen XD (2008), Drying Technology - On measurement of food powder reconstitution properties.
Gaiani C et al. (2007), Journal of Dairy Science - Dairy powder rehydration: influence of protein state, incorporation mode and agglomeration.
Pelegrine DHG & Gasparetto CA (2005), LWT Food Science and Technology - Whey proteins solubility as function of temperature and pH.

*WOO® Shaker Schwarz - available in our shop.*