Which parameters are decisive for efficiently dispersing agglomerates in cocoa powder without increasing dust formation?
In the dry de-agglomeration of cocoa powder, energy input, mixing time, fill level, moisture content and dust-tight product handling are decisive. The aim is to break up soft or loose agglomerates without increasing the fines content and thus the tendency to dust.
Energy input should be no higher than necessary. Excessive speeds, long mixing times or permanently engaged intensive tools can generate additional dust, heat the powder and impair flowability. A gentle base mix with only briefly engaged, locally acting de-agglomeration is advisable. The optimum operating point depends on the fat content, moisture, agglomerate strength and particle size distribution of the particular cocoa powder.
Dust arises above all during container emptying, free powder charging, at transfer points and during discharge. Receiving, dosing, conveying and mixing should therefore take place in as closed a manner as possible. Dust-tight bag-emptying stations, enclosed conveyors, controlled dosing systems and a suitably designed extraction system limit dust emissions. Strong air currents in the mixing chamber should be avoided, as they can stir up fine particles.
Stable moisture control is also important. Cocoa powder that is too dry can dust more, while excessive moisture content reduces flowability and can promote build-up. The optimum setting must therefore be determined with the original product.
In summary, the dry de-agglomeration of cocoa powder succeeds with a precisely dosed energy input, short mixing times and fully closed product handling. This allows agglomerates to be broken up without generating unnecessary fine dust.
How amixon® treats agglomerates in cocoa powder
amixon® combines gentle mixing and targeted de-agglomeration in a single apparatus concept. The base mixing takes place at low tool speed with a controlled, three-dimensional product movement. SinConvex®/SinConcave® helical mixing tools distribute the cocoa powder evenly, without unnecessarily heating it or generating additional fines.
Where agglomerates need to be broken up in a targeted way, separately driven intensive tools are used. They generate increased shear action only locally. Intensity, speed and duration of engagement are set independently of the main mixing tool. This allows soft agglomerates to be released gently, or firmer agglomerates to be de-agglomerated in a targeted way, while the overall batch continues to be moved gently. amixon® describes this approach as de-agglomeration, in which particle clusters can be separated without unnecessarily damaging the primary particles.
The relevant process parameters are stored as a recipe in the PLC. These include mixing-tool speed, the intensity and duration of use of the de-agglomeration tools, and the order of addition. This creates reproducible results and allows adaptation to differing fat contents, moisture levels, particle size distributions and agglomerate strengths of the cocoa powder.
With dusting cocoa powders, amixon® can additionally incorporate a very small quantity of a suitable additive homogeneously. Lecithin is particularly interesting for this in instant cocoa applications. It can be used as a liquid or powdered addition and, with suitable process control, forms a thin film on the powder particles. This film binds fine dust, improves wettability and supports dispersibility in water or milk. The dosage and form of addition must be matched to the recipe, fat content and the desired instant property.
The coating and mixing process takes place in a short, defined time. The aim is not to reduce the size of the cocoa powder, but to distribute the additive evenly while stressing the primary particles as little as possible. The result can be a cocoa powder that is lower in dust, more free-flowing and more easily dispersible.
Discharge also influences dust formation, batch purity and product changes. With ComDisc®, amixon® mixers can discharge up to 99.997% and more of the mix. KoneSlid® mixers are designed for particularly short mixing and residual-discharge times. This reduces residues and thus cross-contamination during recipe changes.
The process is trialled with the original product in the amixon® pilot plant. Mixing quality, de-agglomeration effect, temperature development, dust behaviour, additive distribution, residual discharge and cleanability are examined. This allows the mixing programme, tool configuration and unit size to be matched precisely to the desired cocoa powder quality before the investment is made.