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A case study in precise, continuous mixing: amixon® mixers for infant formula (Part 2)

In both industrial and developing nations around the world, there is a growing demand for manufactured infant nutrition products. The expectations for these products are high: parents rightly expect that infant formula will support the nutritional health of their growing babies.

Because babies only develop a gut microbiome over the course of their first year of life, everything they are fed during this time must be pure and adapted to their specific nutritional needs. Infant nutrition products are specially formulated to resemble the composition of breast milk. Once the baby is older than six months, parents may begin to transition the infant to follow-on milk, whose formula less closely resembles the composition of breast milk.

The role of mixing equipment in ensuring the purity of infant formula

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. In addition to meeting these demands, manufacturers of infant formula also have a vested interest in efficient processing methods.

Modern mixing equipment must be gastight and dust-free in order to protect the mixing goods from environmental influence and protect employees from explosion risks. Containing the dust also has the added advantage of making the system easy to clean and maintain.

The mixer presented in this article, found in an end-of-line facility for infant formula manufacturing, achieves optimum mixing qualities with a minimum energy input in short mixing times. This helps to ensure that the particle structure of the raw materials is maintained and to reduce the number of processing steps necessary overall.

End-of-line mixing for infant formula production

In Part One of this series, the author described a twin shaft mixer for infant formula that can quickly and gently distribute small quantities of trace minerals into dehydrated infant formula components. This twin shaft mixer is not only versatile and easy to clean, but it furthermore offers the unique advantage of needing only one sample per large batch. Such a mixer, however, is decoupled from the filling and packaging process: the homogenized mixture is discharged into an intermediate bulk container and then transported to a separate packaging machine.

This is not the case with end-of-line mixing equipment, where all processing machines are arranged one below the other. In such a setup, the homogenized mixture is discharged from the mixer into an intermediate bulk container that feeds directly into the packaging equipment.

End-of-line systems are typically used for products that must adhere to the same dietary restrictions, e.g. allergenic, non-allergenic, dairy free, Halal or Kosher. This helps reduce the amount of cleaning necessary to effectively prevent cross contamination, as every category of product has its own production line.

    Each filling line consists of two mixers, one for the the batch preparation of goods produced continuously in a spray tower, and another for continuous packaging. The batch sizes generally range from 300 to 1,200 kg. In every case, mixing and discharging takes between two and three minutes.

    Precision and efficiency in infant formula production with KoneSlid®

    The KoneSlid® mixing system was specially developed for processes with such a high degree of variables. Even at low rotational speeds, KoneSlid® mixes gently and precisely, often eliminating the need for preparing premixes. Practical experience has confirmed that even the most delicate agglomerates resulting from spray tower drying, fluidized bed granulation, or vacuum freeze drying are preserved.

    The KoneSlid® mixer can also be made vacuum-tight as needed. By applying a vacuum, it is possible to eliminate atmospheric oxygen from porous powders during the mixing process. Saturation is achieved by injecting nitrogen or carbon dioxide, and emptying takes place without segregation in just a few seconds. Free-flowing goods usually flow out completely, minimizing the risk of cross contamination.

    End-of-line mixers for batch sizes ranging from 300 to 2,000 liters

    Filling levels can vary from 10 to 100 percent. In the case of powders prone to dust explosions, the mixer can be prepared to conform with Ex II 1D (for zone 20) requirements. Furthermore, the mixer can be manufactured to be either pressure shock-resistant or pressure-resistant.

    Large inspection doors prepared using the CleverCut® method offer easy access for manual dry cleaning. The O-ring in the groove seals is very close to the product, practically free of deadspace, making the construction gastight, dust-proof and waterproof. The inspection doors can be opened by manually releasing the KwickKlamp® closures. Electromechanical safety interlocks prevent the inspection doors from opening before the system has been disconnected from power.

    The use of continuous mixers in infant formula manufacturing

    Another method of preparing dehydrated foods such as powdered infant formula is continuous mixing. This is especially beneficial for intermediate goods that are prepared in large quantities over a longer period of time.

    Continuous mixers from amixon® operate according to a “vessel rearrangement” principle. As is typical of continuous mixing, all mixing components are loaded into the mixer via gravimetric dosing while the finished mixture is discharged continuously.

    However, the following makes amixon® continuous mixers unique: Typically, when a conventional continuous mixer is started up, the first of its contents to be discharged do not conform to the overall recipe. This is because the flow rates of each individual feeding mechanism still need to be calibrated. A continuous mixer by amixon®, on the other hand, can also double as a precision mixer, allowing for the calibration phase to be completely accounted for in the resulting mixture.

    At the beginning of the production campaign, the operation proceeds as follows:

    • The discharge valve of the mixer begins in the closed position.
    • All gravimetric feeding mechanisms start simultaneously, initiating a low mass flow rate, and automatically adjusting themselves in relation to one another.
    • The filling level rises gradually, and the mixing action begins once half-capacity has been reached. This is also the point at which transient oscillation in the feeding mechanism is completed.
    • Once the mixer has reached a filling level of 80%, the discharge valve slowly opens. From this point onwards, a filling level of 80% is kept constant. This is possible due to the gradual acceleration of the feeding mechanism until the maximal mass flow rate has been reached.

    At the end of the production campaign, the mixer operation proceeds as follows:

    • All feeding mechanisms gradually slow, reducing the mass flow rate, until they come to stop and close.
    • The mixer then discharges its contents continuously until it is completely empty.
    • The free-flowing goods pour out completely, allowing for every gram of the mixture to be used in the creation of a saleable product.

    Continuous mixers from amixon® operate according to a “vessel rearrangement” principle, making it possible for the mixer to accommodate a wide range of residence times. The mixer can quickly adjust for small fluctuations in the feeding mechanism so that the resulting mixture is unaffected. Furthermore, free-flowing goods can be near to completely discharged.

    In terms of usability, this mixer offers the following advantages:

    • The mixing process is especially gentle, and so a median residence time can be effective for a wide range of filling levels.
    • There is no product loss at the beginning or end of a production campaign.
    • This continuous mixer can double as a precision batch mixer at filling levels of 15 to 100%. This functionality can be useful for the production of premixes.
    • The SinConvex® mixing tool enables quick and complete discharge.
    • Flexible, adjustable settings.
    • Large CleverCut inspection doors enable ergonomic inspection and cleaning.
    • Designed for compliance with even the highest hygiene regulations.
    • Ideal for integration with other continuous production equipment, such as spray towers. At request, can be manufactured for compliance with Ex II 1D for Zone 20 areas.
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