Which criteria should be considered when selecting a spice mixer with integrated liquid dosing?
When selecting a spice mixer with integrated liquid dosing, product quality, process stability, hygiene and safety must all be given equal weight. The central concerns are mixing quality, a suitable form of liquid application and a hygienically designed plant concept that lends itself to automation.
Process engineering requirements
A spice mixer should achieve reproducible, high mixing homogeneity, particularly when very small components such as flavourings, oils or oleoresins are added (e.g. CV ≤ 5 %). The mixing tool must generate enough shear to disperse the agglomerates formed by liquid addition, without excessively damaging the spice particles or causing loss of aroma. Design, tool geometry and circumferential speed are matched to the flow properties, the sensitivity of the particles and the required batch sizes and throughputs; usable fill levels typically lie in the range of roughly 40–70 % of the mixer volume.
Liquid dosing system
Stable formulations call for defined dosing accuracies (roughly ±0.5–4 %). Volumetric systems are simpler, whereas gravimetric systems using load cells are largely independent of fluctuations in viscosity and temperature. The choice between single-fluid or two-fluid nozzles, spray lances or spray bars depends on the viscosity and tackiness of the liquid: low-viscosity media can often be dosed with simple spray bars, while highly viscous or tacky media require finely atomising, compressed-air-assisted nozzles. It is important to position the dosing points in zones of high turbulence in order to avoid local over-wetting, lump formation and build-up; dosing equipment should not obstruct the mixing process and should be easy to clean and maintain.
Hygienic design and cleanability
Spices are microbiologically sensitive natural products, so the mixing chamber and the dosing system should be designed according to hygienic design principles: geometry with minimal dead space, inclined and self-emptying surfaces, product-contact surfaces with low roughness (e.g. Ra ≤ 0.8 µm) and suitable materials (typically stainless steel 1.4404 / AISI 316L). Integrated CIP/WIP systems with strategically placed spray heads and nozzles shorten downtimes and reduce cross-contamination during formulation changes. Seals and elastomers must comply with food law and be sensorially neutral.
Control, safety and cost-effectiveness
Automation should support phased liquid addition (e.g. after a dry mixing phase or at intervals), recipe management and complete batch traceability. Process data such as actual dosed quantities, mixing times and temperatures are documented and ideally integrated into higher-level systems. Because spice dusts can be explosive, a suitable ATEX design (earthing, avoidance of ignition sources, adapted electrical components) is required, along with effective extraction and filtration technology. Maintenance-friendly, readily accessible designs together with energy-efficient drives and a well-considered wear part concept lower life cycle costs and secure economical operation.
How amixon® introduces oils, fats and liquid flavourings into powders without lumps
The liquid is fed in precisely where mixing activity is highest
Lumps usually form through local over-wetting. That is exactly what has to be avoided. amixon® therefore doses via precision addition lances. These can be fitted with single-fluid, two-fluid or multi-fluid nozzles. Depending on the application, the liquid is applied to the moving mix from above or introduced below the fill level directly into the powder bed. That is where the cutting rotor takes effect.
The rotor distributes the liquid throughout the powder in microfine form. The main mixing tool performs the macroscopic blending. It is usually executed in SinConcave®/SinConvex® geometry. ComDisc® tools support virtually residue-free discharge. The result is uniform incorporation combined with a clean mixing chamber.
The two-fluid nozzle produces the finest atomisation. It is particularly suitable for small addition quantities. This applies, for instance, to flavourings or oil-based vitamin solutions.
Rheology and wetting
The properties of the liquid are decisive for the mixing result. Wetting processes are especially difficult when the liquid is highly viscous and the powder is very fine and dusty. The risk of lumps and uneven distribution then increases.
As temperature rises, the viscosity of many liquids falls. This makes them easier to pump, dose and atomise. amixon® mixers can therefore be optionally equipped with a temperature-controlled double jacket. Fats thus remain above their melting point. Cold wall zones are avoided. This reduces build-up and solidification.
Behaviour under shear also matters. Some liquids become thinner at higher shear. Others react sensitively and should be handled with particular care. Nozzle system, temperature and mixing intensity are therefore always matched to the product.
How well the powder can absorb liquid is likewise decisive. A large specific surface area, fine capillary structures and differing particle surfaces strongly influence wetting. From this follow the requirements for droplet size, dosing rate and mixing energy.
A reproducible dosing strategy
The liquid is added continuously and in finely metered form during the batch mixing process. Where fat contents are high, it can be added in several steps with intermediate mixing phases. The process steps can be stored in the PLC.
Mixing intensity is infinitely adjustable. It ranges from gentle moistening to intensive blending. The energy input can thus be adapted to sensitive or robust products.
The fill level can vary between roughly 10 % and 100 %. Mixing quality is maintained even as the fill level changes. When a cutting rotor is used, however, the minimum fill level may be higher.
Plant selection and validation
Depending on the application, vertical mixers, conical mixers or continuously operating systems are used. For demanding products, vertical mixers (VM, SH, HM), conical mixers (AM) or the AMK are employed.
Wetting behaviour, oil binding capacity and dosing strategy are tested in the amixon® pilot plant with original products. This creates certainty for later production operation. With complex powders in particular, this practical test is often indispensable.
Gentle processing of sensitive products
For tea, herbs and spices, amixon® offers particularly gentle mixing processes. Low speeds preserve fragile structures. At the same time they permit virtually complete discharge and rapid cleaning. This is an advantage above all where formulations change frequently.
The Gyraton® GM silo mixer homogenises large batches of spices, tea or coffee ideally, at minimal power input and with particular gentleness. Volumes of up to 100 m³ are possible.
The amixon® conical mixer is especially well suited to what are known as multi-step mixing operations. Premixes can be dispensed with in this way.
Hygienic design as the foundation
All the properties described rest on the amixon® hygienic design. Mixing chamber and mixing tool are welded free of crevices and polished. The mixing tool is mounted at the top only. A critical lower shaft passage is thereby eliminated.
Large Clever-Cut® inspection doors with dead-space-free OmgaSeal® seals provide access to all product-contact surfaces. Dead-space-free discharge devices and integrated washing lances support validatable dry and wet cleaning. This applies in accordance with EHEDG, FDA and 3-A Sanitary Standards. Fully automated cleaning is also available on request.