Securing scale-up trials from the pilot plant to production in animal feed manufacture requires a systematic combination of process characterisation, similarity considerations, statistical trial planning, measurement technology and formal qualification. The aim is to transfer formulation, plant behaviour and product quality reproducibly under realistic production conditions before series production is released.

Defining critical process and quality variables early

The critical process parameters (CPPs) and critical quality attributes (CQAs) should be defined as early as the pilot-plant stage. Depending on the process, these include screw speed, torque, specific mechanical energy (SME), zone temperatures, melt pressure, moisture management, residence time, starch gelatinisation, particle size, bulk density and product texture.

Checking similarity principles for the change of scale

In scale-up, geometric, kinematic and dynamic similarity must be taken into account as far as possible. In practice not all dimensionless characteristic numbers can be held constant at the same time; it is therefore necessary to prioritise which effects are decisive for the product, for example flow behaviour, mixing intensity, heat transfer or residence time distribution. In extrusion processes, specific mechanical energy is frequently used as the central scaling variable.

Securing robustness with design of experiments

A DoE approach helps to develop not just a single successful case but a robust process window. Through targeted variation of relevant factors such as moisture, temperature profile, speed, throughput or conditioning time, main effects and interactions can be identified. This shows which parameters have to be controlled closely in production and where tolerances exist.

Validating raw materials and formulations with representative batches

The raw materials used at the pilot plant should represent later production realistically. Differences in particle geometry, moisture content, bulk density, protein structure or raw material variability can influence the scale-up considerably. Batch traceability and analytical characterisation of the starting materials are therefore essential in order to detect deviations early.

Making inline measurement and process data comparable

Comparable instrumentation in the pilot-plant and the production plant facilitates direct comparison of the data. Typical measured variables are pressure, temperature, torque, moisture, spectroscopic signals or, where applicable, water activity. PAT concepts support real-time monitoring and help to detect and correct deviations during the scale-up immediately.

Assessing thermal and mechanical loads separately

In drying, cooling and conditioning processes, heat transfer, residence time and thermal inertia often change at a larger scale. This can affect product safety, residual moisture and texture. Mechanical loads such as shear or pressure can also change the rheology and thus forming, expansion or mixing homogeneity. These effects should be investigated deliberately at the pilot plant and transferred to the production plant.

Testing quality not only technically but also functionally

Depending on the product, sensory, physical and nutritional characteristics must be confirmed alongside the process engineering data. These include, for example, hardness, bulk density, degree of expansion, sinking behaviour in aquafeed, palatability, digestibility and microbiological safety. The product quality at production scale should be compared systematically with the pilot-plant product.

Planning risk analysis and qualification

An FMEA helps to assess typical scaling risks such as wear, segregation, hotspots, insufficient drying or microbiological risks in a structured way. Before the plant is released, the qualification stages IQ, OQ and PQ should also be completed in order to demonstrate installation, function and reproducible performance.

Setting up documentation and knowledge transfer properly

All trials, deviations, corrective measures, measured data and release criteria should be documented in a structured transfer report. This facilitates traceability, supports later audits and creates the basis for a stable production start-up. Uniform terms, clear definitions and consistent data documentation are decisive here.