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Two amixon® mixers with mirror polish. These mixers are automatically wet-cleanable and sterilizable. The batch size is 2400 liters. The mixers are used to prepare powdered penicillin.

Hygienic design and HACCP for mixing powdery or moist food products

The idea of “Hazard Analysis and Critical Control Points” was born at the NASA in 1958. The intent was to establish guidelines for the production, storage, and processing of space food.

Later, the principles were adopted by the WHO Codex Alimentarius Commission: Hazard analysis - critical control points - limits - continuous monitoring - corrective actions - documentation - periodic verification.

In the EU, the obligation to implement HACCP has been regulated since 2006 in Regulation (EC) No. 852/2004 concerning the hygiene of foodstuffs. Process machines for food production comply with minimum hygienic requirements in order to implement HACCP. The EHEDG, for example, could also offer its services here. The "European Hygienic Engineering and Design Group" pursues the goal of promoting food safety. The members of the EHEDG are mechanical engineering companies, food producers, research institutes and health authorities. In this respect, it also advises European boards on the drafting of statutory hygiene guidelines.

For example, the EHEDG evaluates construction materials and their industry-specific suitability. Numerous mechanical engineers are contributing improved design ideas to the decision-making panels of the EHEDG. It can carry out practical cleaning tests and issue hygienic design certificates for good cleanability.

The EHEDG endeavours to exchange ideas with the US government agency NSF (National Sanitation Foundation*) and the non-profit American organization 3-A SSI (3-A Sanitary Standards**) in order to establish transatlantic common views.

  *) The NSF is a US government agency for basic research and education in food engineering.
  **) The 3-A SSI is a nonprofit organization in the United States that targets good hygiene designs in the food, beverage and pharmaceutical industries. It also certifies components based on strict theoretical design requirements, material specifications and surface conditions. However, qualifications through practical cleaning tests are not part of the 3-A SSI certificates.

    amixon® precision mixers are used for the preparation of a wide variety of nutritional and culinary products. In this respect, they must meet the highest hygiene requirements.

    Vertical precision mixers: machine design and mixing principles

    The mixing systems presented here have different key areas of application. However, they feature the same hygienic characteristics. They mix extremely gently at low rotational frequencies and avoid product heating as well as "product rubbing" on the mixing chamber walls. The mixing shaft is sealed and driven only from the top, out of contact with the mixing goods. There is no sealing in the mixing room floor. The mixing tools of all mixers are welded and polished without joints. The gas-tight shaft seal is designed as a PTFE lip seal and — both dry and wet — can be controlled microbiologically. The mixing space is also welded and polished without joints. The closing elements on the bottom side seal dead space-free and gas-tight.

    Particular properties of the cone mixer should be pointed out at this point. It realizes ideal mixing qualities starting at filling levels of 5% to 10%. So-called multi-step mixing processes are often used in the flavor and spice industry for mixtures of complex ingredient compounds: Partial filling takes place first, followed by intensive mixing with dosed addition of liquid additives. After obtaining an ideal mixing quality, sensitive components are then added, which are “lifted in” particularly gently at a low rotational frequency. This procedure replaces small mixers, which are used to produce so-called premixes. Due to the conical design, the bulk materials are discharged - usually completely - without segregation with the mixing tool rotating slowly.

    SinConvex® and SinConcave mixers transport the mixes mixing goods upwards in the periphery of the mixing chamber. Once at the top, the goods flow downwards in the center of the mixing room and drift outwards again. Dry, moist or suspended materials are ideally mixed with precision — regardless of differing particle sizes, bulk densities, flow properties and the rotational frequency of the mixing unit. After 30 to 100 revolutions, the mixing quality is usually ideal.

    Inspection doors and their seals

    Companies producing baking agents or seasonings often use their mixers for 30 years or more. Mixing tasks change frequently, on some days 15 times or more.   In the process, the inspection doors are repeatedly used for the purpose of cleaning and revision. Opening and closing must be ergonomic and reliable. amixon® has developed KwickKlamp® door locks. They are easy to use and close permanently in a self-locking manner.

    amixon® can also manufacture a wide variety of door seals, but inspection doors of a powder mixer are only particularly good if they close without dead space. With the OmgaSeal® variant developed by Clever-Cut® , we offer an inspection door with a dead-space-free seal. It is manufactured very precisely and is permanently gas-tight.

    amixon® inspection doors are manufactured as standard with the OmgaSeal® seal shown on the left. It is practically free of dead spaces and permanently gas-tight. Other designs, as shown on the right, have dead spaces in the form of gaps. They are not manufactured by amixon®.

    Self-cleaning via complete discharge of residues: SinConcave mixing tools allow the mixing goods to drain off completely.

    The mixing tools are welded and polished without joints. They are only driven and supported from above. The shaft passage is equipped with a lip seal. This can be designed to be splittable on request and allows a worn seal to be replaced with minimal effort.

    Flat-bottom mixers can also achieve excellent levels of residual discharge if the lower mixer arm is fitted with so-called ComDisc® tools.

    SinConcave® designed mixing spiral. Normally, a mixing tool helix has a slope of ALPHA = 17° to 21°. Some mixing materials are adhesive; in this case, it is possible that they do not flow off completely during the discharge. amixon® can tilt the helix of the mixing unit convexly or concavely by the angle BETA. The effective discharge angle EPSILON is then 30° or more. Bulk materials then normally flow off completely.

    If the amixon® mixer has a flat bottom, ComDisc® tools can discharge the mixing goods almost completely. This increases the utility of the mixer and helps preserve raw material resources.

    During mixing, the ComDisc® elements float in the flow shadow of the lower mixing arm. When the discharge of the mixing goods takes place, they lower and gently sweep the bottom of the mixing chamber. They act like a windshield wiper. They are arranged obliquely and push the material residues into the discharge nozzle. Residual discharge after each batch can unlock a big win for the company. Especially when constantly varying recipes are mixed.

    ComDisc® tools are made from food-safe materials and are particularly wear-resistant. They are installed “captive” and can be replaced as desired.

    An amixon® cone mixer can also discharge completely if the mixes are free-flowing.

    amixon® cone mixers and also KoneSlid® mixers can completely discharge down to a few grams of dust if the mixing goods are free-flowing. A comparison of wet and dry cleaning can be read here.

    amixon® conical mixer type AM in a particularly hygienic design. The Washing-in-Place system can be seen on the left.

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