What must be considered when wetting powders with oils or fats in order to avoid lump formation?
When wetting powders with oils or fats, what is decisive is that the liquid phase is finely distributed, dosed and completely incorporated. Lumps usually arise where the liquid is added too quickly, too locally or with too little shear, so that a wetted shell forms on the outside while the interior remains dry.
1. Viscosity and temperature
Oils and fats are often viscous, which means the liquid phase spreads more slowly within the powder bed. Moderate heating can lower the viscosity and make wetting easier. With solid fats the temperature must be chosen so that the fat phase reliably remains liquid, without subjecting the product to unnecessary thermal stress.
2. Feed the liquid in slowly and evenly
The liquid should be added continuously and in fine doses, not abruptly. Good distribution within the mixing chamber is particularly important so that no locally over-wetted zones arise. Sequential addition with intermediate mixing phases is advisable where larger quantities of fat are to be incorporated.
3. Atomise the liquid phase finely
Spray nozzles or other atomising systems help to convert the oil or fat phase into small droplets. The finer the droplets, the greater the contact area with the powder and the lower the risk of liquid bridges and lump formation.
4. Introduce the powder in a controlled manner
Where powder is added onto an existing oil phase, a core-shell effect can arise: wetted on the outside, dry inside. The dosing strategy is therefore decisive. In many cases it is better to introduce the powder continuously and well distributed into the moving liquid phase or into an intensively blended product bed.
5. Sufficient shear, but not too much
In order to break up dry agglomerates and work the liquid into the powder bed, a certain mechanical intensity is often necessary. Too little shear leads to incomplete wetting; too much shear can stress the product unnecessarily or lead to excessive heating. What is decisive is targeted deagglomeration without destruction of the product.
6. Get air out of the product
Powders contain a great deal of entrapped air. This must be displaced during wetting, otherwise dry cores and unstable micro-agglomerates remain. Vacuum assistance or venting phases can improve wetting considerably.
Important rule of practice
Lump formation is best avoided where viscosity, temperature, dosing rate, atomisation, mixing intensity and venting are optimised together. Particularly critical are rapid liquid addition, uneven distribution and insufficient shear.
How amixon® solves the lump-free wetting of powders with oils and fats
amixon® mixes powders with oils and fats in such a way that the mixture stays cool, remains free-flowing and is easy to fill. That is particularly important with recipes containing carrier oils, flavourings, lecithins or lipophilic active substances, because the development of heat and local over-wetting can quickly lead to lump formation.
Liquid input at the right place
The main cause of lumps is local over-wetting. amixon® counters this with a targeted liquid addition: oil or fat is introduced directly into the active mixing zone via feed lances, single- or two-fluid nozzles or other dosing systems.
There the liquid phase is immediately distributed within the product, so that pockets of liquid and agglomerates cannot arise in the first place.
Rotor-stator effect for micro-distribution
For particularly effective deagglomeration, amixon® has very effective rotor-stator systems available. These can distribute the liquid phase microfinely and break up local lump formation in a targeted manner.
What matters is this: the rotor-stator is used only where the recipe calls for more intensive local processing. The overall batch continues to be guided within the gentle overall flow of the mixer.
The mixture stays cold and therefore free-flowing
An essential advantage of amixon® mixing technology is that the mix stays cold during the process or is heated only minimally.
Fat-coated mixtures can thereby be set so that they remain free-flowing and are easy to fill. With suitable temperature management, a fat phase that has briefly melted after input can even cool down again far enough for the mixture to remain stable, dry to the touch and easy to dose.
Dosing strategy and adjustable intensity
The mixing intensity is infinitely adjustable depending on the product: from gentle wetting to the more intensive incorporation of high fat contents.
The continuous, finely dosed addition with intermediate mixing phases can be stored as a recipe in the PLC, so that every batch is run reproducibly.
Flexible in fill level and product change
With many amixon® systems the fill level can be varied across a wide range. That is important where the oil binding capacity of the powder or the batch size fluctuates.
Precisely for baking agents, instant products, animal feed, detergent compounds or similar recipes this is an advantage, because wetting succeeds without lump formation and with stable product quality.
Testing in the pilot plant
Whether wetting behaviour, oil binding capacity and dosing strategy lead to the desired quality is examined in advance by amixon® in the pilot plant with the original product.
Mixing intensity, choice of nozzle, temperature management and product behaviour are matched there so that a homogeneous mixture results which stays cool, remains free-flowing and is easy to fill.