Hygienic design for processing powdered or moist foods

Visit us:

Interpack Düsseldorf, booth 1D-18 in Hall 1

Audits are generally seen as cause for concern. Processes are interrogated with academic rigour by outsi-ders and a spotlight is shone on the less attractive areas of production. Apparently trivial documents must be produced and some experienced production teams have felt undermined by the questions of an auditor from the town hall. There is no respite until the ordeal is over and the list of defects is brief and, ideally, quickly addressed. And despite every care, an audit can also fail. Because if you look hard enough you will find something.

Quality assurance and training is a major industrial sector which has a mutual relationship with the standards system and which is a major lobbyist up to and including the legislative process. Quality regulations are changing all the time therefore, sometimes without real need. Some food producers would rather invest the money they spend on the resultant expenses on modernising their process engineering equipment. In truth, any production operation is dependent on its good quality in order to survive. Their aim is to please, to de-light, their customers. Quality is what the customer expects. Only then is it possible to make a profit.

Food producers are well advised to integrate a dynamic quality assurance system into their production ma-nagement or directly into their ERP system and ideally to monitor all process stages from the perspective of quality assurance. It therefore makes sense to adopt a HACCP concept. A HACCP concept identifies all risks, selects local control points and defines limit values. An embedded, integral ERP system is used for process control. It documents all production-relevant, operational profit-related data as well as hygiene as-pects and also fulfils statutory conditions.

The idea of “Hazard Analysis and Critical Control Points” came from NASA’s “Risk Based Hazard Analysis” in 1958. The aim was to establish regulations for the manufacture, storage and processing of food for astro-nauts. Subsequently the principles of the WHO's Codex Alimentarius Commission were adopted: Hazard Analysis - Critical Control Points – Limit Values - Continuous Monitoring – Corrective Measures – Documen-tation - Regular Verification.

In the EU, the obligation to use HACCP has been part of (EC) regulation no. 852/2004 on the hygiene of foodstuffs since 2006.

Process machinery for food production must meet minimum hygiene requirements in order to be able to implement HACCP. This is where the European Hygienic Engineering Design Group (EHEDG) comes in, with its primary aim of promoting food safety. It does so by providing assistance to food companies to im-plement the statutory hygiene regulations. Members of the European Hygienic Engineering Design Group are device manufacturers, food producers, research institutes and health authorities. To this extent it also sup-ports the European legislature in devising food hygiene regulations and machine directives. The EHEDG also devises recommendations for construction materials and their respective compatibility for contact with diffe-rent foods. Corresponding guidance is announced, published and disseminated via seminars by the EHEDG. Food machinery and equipment engineers are well-advised to follow the technical design recommendations of the EHEDG and, where appropriate, to submit their own design ideas to the decision-making bodies. The EHEDG offers machinery and system engineers the opportunity to have their components assessed and certified in accordance with the hygienic design requirements.

The EHEDG also collaborates with the US NSF (National Sanitation Foundation) and the non-profit US orga-nisation 3-A SSI (3-A Sanitary Standards) to define joint handling structures at an international level.

  • *) The NSF is a US government agency which supports principle research and training in all non-medical areas of science and technology.
  • **) The 3-A SSI is a non-profit organisation in the USA, whose aim is to improve hygiene design in the food, drinks and pharmaceutical industry. It also certifies components based on strict theoretical design requirements, material specifications and surface qualities. Qualification via practical cleaning tests is nevertheless not a component of the 3-A SSI certificate.

A huge range of precision mixers for wet and dry foods is used in the food industry throughout the world. Practically all food mixers supplied in Europa meet the minimum hygiene requirements.

Food mixers from some European mechanical engineering companies even meet hygiene requirements which far exceed the directives of EHEDG and 3-A SSI in order to free the operator from any hygiene risk. Paderborn-based amixon GmbH complies with particularly high design hygiene standards.

Vertical precision mixer; machine design and mixing principle

The mixing container stands upright. Helical mixing tools in the patented SinConvex® design rotate in the centre of the mixing chamber, generating a highly efficient product flow. The helical blade gathers the mix-tures at the periphery of the mixing chamber and transports them upwards. Once it reaches the top, the product flows downwards in the centre of the container. Dry, moist or suspended materials are ideally mixed in the form of a classic thrust flow at a slow rotational speed, irrespective of different particle sizes, bulk densities and flow properties. The mixing effect essentially takes place at the interfaces between the two macro-currents. The particular geometric characteristics of the mixer produce optimum mixing qualities after about 30 to 200 revolutions, effectively the best possible performance.









These mixing systems are designed for different applications. However, they exhibit the same hygiene quali-ties. They mix extremely gently at low speeds, avoiding product heating and “product wear” on the mixing chamber walls. The mixing tools are only mounted and driven from the top. There is no seal on the mixing chamber base.

The mixing tools of all mixers are seamlessly welded and polished. The shaft has a gastight PTFE lip seal and is microbiologically controllable, wet or dry. The mixing chamber is also seamlessly welded and polis-hed. The underside closure devices create a zero-clearance and gastight seal.

At this point we refer particularly to the characteristics of the conical mixer. It achieves optimal mixing quali-ties at filling levels of 5% to 10%. So-called multi-stage mixing processes are often used for complex product blends in the aromatic and spice industry: Initial partial filling is followed by intensive mixing with the metered addition of liquid components. Once an ideal mixing quality is achieved, delicate ingredients are then added and gently “folded in” at ultra-low speed. This process replaces the use of small mixers to produce premixes. Due to the conical design, the bulk materials are discharged - completely in the case of free-flowing materi-als - without segregation with the mixing tool rotating slowly.

The design details below add further benefits for mixing operations:

Let’s look for example at the inspection doors in this mixer. Large scale, they enable extremely rapid opening and closing while being permanently gas and liquid-tight. The key feature of the doors however is the location of the O-ring seal. It is particularly close to the contour of the mixing chamber and is zero-clearance.


The automatic wet cleaning of the mixer, unlike standard inspection doors, is particularly dependable.


The mixing tools are designed in accordance with the SinConvex® design. They are particularly effective and fast. They also enable very much better residue-free emptying than a standard helical mixing tool.

SinConvex®-design mixing tool

SinConvex®-design mixing tool

Standard helical mixing tool

Standard helical mixing tool

The mixing tools are welded without seams and polished. They are mounted and driven only from above. The shaft bushing is fitted with a lip seal. This can be a split seal if required and allows replacement of the worn seal with minimal effort

Flat-based mixers can also exhibit excellent residue-free emptying if the lower mixer arm is fitted with Com-Disc® tools.


ComDisc® tools enable residue-free emptying in flat-based vessels.

amixon® mixers correspond to EHEDG and FDA specifications and therefore meet the highest standards for the hygienic preparation of high-quality powdered products such as aromatics, baking premixes, nutrients and seasonings, dietary supplements, baby food and pharmaceuticals. Moreover, they meet all requirements contained in the GMP standard.

amixon® AM conical mixer in ultra-hygienic design

amixon® AM conical mixer in ultra-hygienic design

Meet our experts on LinkedIn



Visit us: Interpack Düsseldorf, booth 1D-18 in Hall 1

Please feel free to contact us!

amixon GmbH
Halberstaedter Strasse 55
33106 Paderborn
Phone: +49-5251-688888-0
Fax: +49-5251-688888-999

I have read and agree to the privacy policy *