A case study in precision batch mixing: amixon® mixers for infant formula (Part 1)

In both industrial and developing nations around the world, there is a growing demand for manufactured infant nutrition products. It goes without saying that all foods formulated for consumption by infants must meet stringent standards for nutritional value and food safety. These demands can only be met if the raw material components are prepared in quality-controlled systems.

The role of mixing equipment in ensuring the quality of infant nutrition products

Mixing is a crucial processing step in determining the resulting product quality. It is at this stage that microscopic particles such as probiotics, minerals, and trace elements like zinc, copper, selenium, and chromium must be precisely and evenly blended in with the bulk powders prior to packaging.

Mixing infant formula is a challenging task, as the entire process must use only minimal energy input in order to preserve the delicate particle structures of the powders. On top of this, the resulting mixture must be dust-free, uniformly dissolvable, and homogenously blended. These characteristics are essential if the resulting infant formula powder is to make for a nutritious product to support the health of growing babies.

Infant formula mixing challenges in high-volume operations

A modern filling and packaging machine can process a flow volume of roughly 20 cubic meters (roughly 10 tons) per hour. In order to work at this pace, infant formula manufacturing facilities must have a logistic concept capable of coordinating the various processing stages and equipment involved.

Generally speaking, there are two ways to approach mixing in a high-volume manufacturing setting such as this:

  1. A single precision mixer with a batch volume of 10 or more cubic meters may be implemented such that it feeds into multiple filling machines.

  2. Multiple smaller mixers with batch volumes ranging from one to two cubic meters may be implemented, each feeding into its own dedicated filling machine. This is called an end-of-line operation.

Both of these approaches to high-volume mixing call for the following basic requirements:

  • ideal results in short mixing cycles
  • gentle handling to preserve delicate particle structures
  • dust-free processing to the highest degree possible
  • produce powders with excellent sinkability and solubility characteristics
  • a quick and efficient discharging process
  • excellent hygienic design and ergonomic, inspection-friendly construction to facilitate cleaning

Quality and efficiency in infant formula production with the Twin-Shaft Mixer HM

The twin-shaft mixer HM from amixon® offers a particularly gentle yet effective solution to the challenges of manufacturing large volumes of powdered baby nutrition products.


The construction and flow principle of the twin shaft mixer HM from amixon®.

The mixing vessel consists of two cylinders that have been fused together, each of which houses a spiral mixing tool. Both mixing spirals rotate in the same direction and are designed with a slight incline of 30°. The diameter of the mixing tool is wide enough to convey nearly a quarter of all the goods within the vessel in just a single rotation. The peripheral speed of the mixing tool is typically adjustable between 0.5 m/s to 3 m/s.

The helical blades gather the powdery contents at the periphery of the mixing vessel, conveying them upwards. Once the powders have reached the top, they then flow back down along the center of the vessel. A three-dimensional current is created in the space between the upward flow at the periphery and the downward flow in the center. The actual mixing, i.e. particles changing places with one another, happens between these two macro flows.

Designed to create this three-dimensional flow even at extremely low filling levels, the twin-shaft mixer HM can effectively create a homogenous mixture even with a volume of just 10 to 15 percent its capacity. An amixon® mixer with a volume of 10,000 liters could mix a thousand-liter batch just as well as a 10,000-liter batch.

Because the mixing action proceeds without any deadspace, technically ideal mixing qualities can be achieved in as few as 20 to 90 revolutions, after which the homogeneity is virtually impossible to improve any further. The mixing process is particularly gentle and energy efficient, making it ideal for high-volume applications in infant nutrition manufacturing.

Bild eines Mischer HM 10.000
A 3D rendering of a twin-shaft mixer with a useable volume of 10 m³. This mixer is equipped with four simultaneously operating discharge valves and eight CleverCut® inspection doors.

amixon® mixers and your infant formula production line

The mixer is loaded with individual components from above via one or more feeding connectors; loading can take place batch-by-batch, or continuously. If the mixer is situated on top of loading cells and can also function as a hopper scale, it can be stationary. In the case that batches must be mixed in quick succession, the mixer can also rotate.

After just one to four minutes, the mixing process is complete, and a discharge valve, flush with the floor of the mixer, opens. The mixing goods flow downwards out of the mixer. Discharging proceeds without any segregation and the size of the volumetric flow is determined by the dimensions of the stop fittings.

In high-volume manufacturing applications, this twin-shaft mixer offers three particular advantages. First, only one sample analysis must be performed per batch. Second, the mixer can be configured to discharge into multiple filling machines. And finally, because mixing and filling take place in separate stages, the mixer can even be cleaned while the filling machines are still in operation.

On request, this mixer for baby formula manufacturing can be constructed to be vacuum- and pressure-tight. This could be beneficial, for example, should loading take place via a pneumatic vacuum system. In other applications, all atmospheric oxygen must be eliminated from the mixing vessel before feeding by generating a vacuum of approximately 50 mbar gauge pressure. In this case, the mixing chamber can be flooded with nitrogen gas before the introduction of the mixing goods. This requires maintaining a gentle positive nitrogen pressure of 50 to 100 mbar within the chamber during mixing and discharging in order prevent oxidization. Another use case for a vacuum- and pressure-tight system would be applications where loading the mixing vessel takes place via a pneumatic pressure system. Even during operation under extreme pressure, the mixing vessel re-mains gastight and dustproof. This applies in particular to complex structural elements such as the shaft seal, floor sealing valve, and the inspection door.

Cleaning and inspecting infant formula mixing equipment

Any facility manufactures infant formula alongside other products can only guarantee allergen-free processing by means of thorough wet cleaning protocols. amixon® mixers simplify the wet cleaning and subsequent drying process with an innovative system called WaterDragon®, a series of rotating wash nozzles permanently in-stalled within the mixing chamber.

When the mixer goes into wet cleaning mode, these nozzles emerge from behind seamless closure flaps and extend into the mixing vessel. Driven by as little as 3.5 bar of water pressure, the heads of the wash nozzles rotate while spraying from three different outlets, dousing the interior of the mixing vessel. Depending on the size and application, amixon® mixers may need to be equipped with three to five WaterDragon® nozzles in order to effectively clean every surface within the mixer. Once the interior of the mixer has been sprayed down, excess water flows out of the mixing chamber, and warm air is funneled into mixer through the WaterDragon® nozzles.

amixon® mixers are also particularly user-friendly for manual dry cleaning methods, as the large, ergonomic inspection doors offer easy access to the mixing chamber. These doors are produced using the CleverCut® method, during which an O-ring is inserted into the groove, creating a gastight, dust-free seal that is very close to the product and free of deadspace.

Experience the difference for yourself

Each infant nutrition manufacturing facility has its own unique production line. As such, every piece of industrial mixing equipment must be engineered for the customer’s specific needs. In order to give customers a chance to try our mixers for themselves, amixon® has test mixers available for trial runs in seven countries from North America to Europe to Asia. Our process engineers have many years of relevant market experience in regions across the world. Our team of 142 employees carefully custom-builds every single one of our mixers according to detailed customer specifications in house at our production site in Paderborn, Germany.