What requirements do infant formula manufacturers place on dead-space-free designs and complete residual discharge?
Manufacturers of infant formula are subject to particularly high hygiene requirements owing to the especially vulnerable target group and strict regulatory specifications, including Codex Alimentarius, EU Regulation 2016/127, FDA 21 CFR 106/107 and FSSC 22000. Central criteria for the process engineering plant design are dead-space-free constructions and complete residual discharge, in order to reliably avoid microbiological contamination – particularly with Cronobacter sakazakii and Salmonella spp. – as well as cross-contamination between batches.
Requirements for dead-space-free constructions
A dead-space-free construction means a plant design in which no zones arise where product, cleaning media or moisture can stagnate and which thereby become niches for microorganisms or biofilms. Typical requirements are:
Geometric dead space limitation (L/D ratio)
Branches, dead legs and sensor connections must be executed so that the ratio of depth L to diameter D does not exceed defined limits. According to EHEDG, an area is regarded as critical where L is greater than D; in infant formula production an even stricter criterion of L ≤ 0.5 · D is frequently required, in order to ensure reliable flow-through in the CIP process.
Flow guidance and CIP compatibility
Product-contact areas are to be designed so that sufficient flow – generally turbulent flow in the high Reynolds number range – is achieved across the entire surface during production and cleaning. This reduces deposits and the microbiological load and is a prerequisite for reproducible CIP and SIP processes.
Radius specifications and surface finish
Internal edges and transitions must be executed with suitable minimum radii, typically at least 3 mm, in order to improve cleanability and to avoid notches and stress cracks. Welds are ground flush and polished to the level of the adjoining surfaces, with roughness values of Ra ≤ 0.8 µm, in critical zones often Ra ≤ 0.4 µm, electropolished where applicable.
Crevice-free connection technology
Hygienic welded joints – for example orbitally welded and root-side purged – are preferred over detachable connections. Where screwed connections are necessary, hygienic or aseptic sealing systems with defined compression are used, in order to avoid crevices and crevice corrosion zones.
Instrumentation (sensors)
Sensors for temperature, pressure, conductivity and so on are to be installed flush-mounted, so that no recessed pockets arise in which product residues can remain.
Valve and fitting geometry
Valves used – for example diaphragm, seat or mixproof valves – must be designed so that the full cross-section is released in the open state and the closure is flush with the inside of the pipe in the closed state. Classic tees are replaced by flow-optimised short tees or block-shaped valve matrices, in order to minimise dead spaces and deposit zones.
Requirements for complete residual discharge (drainability)
Complete residual discharge of product and cleaning media is essential for infant formula manufacturers, both for reasons of product safety and for process efficiency:
Pipe routing and gradient
Pipes are to be laid with a continuous gradient of typically 1 to 3 per cent in the direction of flow. Horizontal sections without a gradient are to be avoided, in order to exclude residual pools, product films and detergent residues. Transitions between different pipe diameters are executed with eccentric reducers, so that a level invert arises for unimpeded drainage.
Self-drainage of components
Vessels, heat exchangers, filter housings and pipes must be designed so that they can be emptied completely by gravity without mechanical aids. This includes, among other things, conical or torispherical vessel bottoms with a central outlet, the avoidance of horizontal flange surfaces in the product area as well as internals only where they are accessible and drainable for cleaning purposes.
Surfaces and product adhesion
As with freedom from dead space, smooth, defect-free surfaces with a defined roughness play a central role. They minimise the adhesion of powdered and protein-containing residues, facilitate the complete removal of product after production and reduce drying times after CIP.
Avoidance of cross-contamination and microbiological risks
Fully drainable systems ensure that no product residues remain when formulations or batches are changed, which is decisive particularly with allergen-free or medically indicated special formulas. At the same time, moisture niches are avoided that could otherwise serve as a breeding ground for biofilms and pathogenic organisms.
CIP and SIP capability and process efficiency
Complete drainability facilitates the reliably dimensioned dosing of CIP media and prevents their dilution by residual liquids. It increases the effectiveness of thermal sterilisation (SIP) and contributes to shortening cleaning and drying times as well as to increasing plant availability (OEE).
Verification and validation of the requirements
Compliance with the requirements for freedom from dead space and drainability is systematically checked and documented in the infant formula industry, typically as early as the FAT phase (factory acceptance test):
Riboflavin test (EHEDG Doc. 2)
Fluorescence-based test to check whether cleaning media reach all product-contact surfaces and no poorly accessible areas (dead spaces) remain.
Drainability tests
Defined filling of plant components with water and measurement of the residual volume after discharge, in order to demonstrate complete residual discharge.
Swab and rinse tests
Microbiological tests after CIP, in order to ensure that no hygienically relevant residues remain.
Measurement of the surface finish
Documented roughness measurements at critical points – for example welds, transitions and corners – to confirm the specified Ra values.
EHEDG and 3-A certifications
Use of certified components and preparation of declarations of conformity as evidence that the components used and the overall design comply with the recognised hygienic design standards.
How amixon® implements dead-space-free construction and hygienic design
Freedom from dead space as a design principle
In amixon® precision mixers such as VM, HM, AM, SpherHelics® and KoneSlid®, the mixing chamber and mixing tool are welded free of crevices and ground smooth. There are no crevices, bolted connections or capillary gaps in the product-contact area, and the mixing tool is mounted and driven exclusively from above, so that the classically contamination-critical lower shaft passage is eliminated.
The standard connection with discharge flap closes flush and dead-space-free with the inner wall of the mixing chamber; dead-space-free ball segment valves are available as an alternative. The large inspection doors are manufactured by the Clever-Cut® process and seal permanently dead-space-free with the OmgaSeal® door seal, on request vacuum-tight or against overpressure.
Cleaning: wet and dry, validatable
Integrated washing lances enable wet cleaning of the mixing chamber; on request, amixon® supplies fully automatic wet cleaning. The amixon® target-jet cleaners are freely programmable and thereby help to save water and to shorten the washing process. The SinConvex® mixing tool supports the complete drainage of product and cleaning medium. The mixers are designed for dry and wet cleaning regimes, so that changing between dry cleaning and wet cleaning is provided for.
The Clever-Cut® doors provide complete, ergonomic access to all product-contact surfaces and thereby form the basis for visual cleaning inspection as well as sampling within the scope of swab and rinse tests. amixon® also has a method for drying the cleaned mixer quickly and effectively in a cold state.
Certified standards
On request, amixon® mixers meet the EHEDG guidelines, the FDA hygiene guidelines, the design specifications of the 3-A Sanitary Standards and GMP requirements. VM and HM can be used FDA-compliantly as sterile mixers and reactors. The ComDisc® residual discharge – 99.997 per cent and better with free-flowing goods – minimises residues and cross-contamination risks when formulations are changed.
In dairy and infant formula production, amixon® mixers are in use worldwide at manufacturers and contract manufacturers: vitamins, minerals, trace elements, encapsulated omega-3 fatty acids and probiotics are mixed in homogeneously and gently downstream of the spray tower – without destroying agglomerates.
Manufacture in Paderborn as the quality foundation
amixon® develops and manufactures exclusively at the Paderborn works with a high depth of manufacture and all components from Germany. As a certified welding company with European, Japanese, Korean and American qualifications, amixon® designs every apparatus as a one-off on the basis of the operator's URS, and quality control remains entirely in-house without gaps. This manufacturing autonomy also secures long-term supply, since every component can be reproduced even decades later.
Verification in the amixon® pilot plant
amixon® checks in advance in the pilot plant, with 35 test units, whether the specific formulation delivers the expected results. Trials with the original product under real conditions are carried out, evaluated and documented jointly and serve as a robust basis for decision-making before the investment.