The 5 key steps of validating aseptic processing / filling systems

20 January 2026 | David Whittaker, Process Innovation Lead, Rob Limburn, Section Lead – Industrial Process Microbiology, and Anna Del Ciondolo, Thermal Processing Team Manager

Producing safe food / drink is the main responsibility of any food business operator. The correct management of microbiological hazards is to be proven by a carefully designed HACCP system. Validation is the process that will demonstrate whether the HACCP will work in theory and in practice, firstly by collating the relevant scientific documentation and secondly by demonstrating the plan works in operation (under worst-case conditions).^{1, 2} Therefore, conducting a validation will display to customers and regulators that the required due diligence is being carried out, enhancing the commitment to public safety, and hence trust in the brand (or products).

In the specific context of continuous aseptic processes, a well-planned and executed validation is paramount to ensure that the processes applied always guarantee the required product safety and quality.

Aseptic processing is the method of producing heat-treated, sterile product and filling into sterilised containers under aseptic conditions. Within an aseptic processing line, food safety risk can arise from an insufficient thermal process of the product, from a breach of sterility of the packaging or filling environment, or from the filling line itself (due to inadequate cleaning and sterilisation processes).

The complexity associated with the design of an aseptic process and filling line inherently requires a multi-stage validation approach, to confirm that commercial sterility is always achieved.

A comprehensive approach to an effective aseptic process line validation can be summarised in 5 key steps:

1. Validation of the product thermal treatment;
2. Validation of the Clean-In-Place operation;
3. Validation of the fillers and filling environment decontamination;
4. Validation of the packaging decontamination;
5. Microbiological assessment of a test production run.

The 5 steps in validating a continuous aseptic process line

1) Validation of the product thermal treatment

Raw product formulations often harbour a multitude of microorganisms, present as vegetative cells and/or spores. Depending on the product’s pH level, and intended shelf-life, a sterilisation or pasteurisation process is needed to eliminate the relevant microbiological risks and guarantee a commercially sterile product. The thermal process (sterilisation or pasteurisation) in a continuous flow line is delivered in the holding tube; a section of pipework designed such that the product is held at the required temperature for a fixed time.

Therefore, validation of the thermal process requires:

• Knowledge of the appropriate target microorganism target and its heat resistance;
• Calculation of the worst-case product residence time in the holding tube;
• Assessment of the worst-case temperature achievable in the holding tube.

The thermal process attainable in the line can ultimately be determined by calculating the process lethality, under worst-case product and process conditions.

Activities such as equipment qualification, product rheological testing and live process test runs should all be used as technical knowledge base to support the thermal process validation.

For any aseptic process line, the validation of the product thermal treatment should be carried out whenever a new line is installed, a significant product change has occurred, or modification to the holding tube, heat exchanger and other key instrumentation has taken place.

2) Validation of the Clean-In-Place (CIP) operation

Before any production run begins, the aseptic process line will undergo a Clean-In-Place (CIP) operation. During a CIP, the process line is not disassembled for cleaning; instead, cleaning solutions and rinse water are pumped through the system under defined conditions of flow rate, chemical concentration and temperature, following the same path as the product.

A CIP procedure should be validated under worst-case conditions. For example, the most difficult product to clean, the longest production run, the maximum allowed time between end of production and start of cleaning, the least optimal temperature, flow or cleaning agent concentration. Location and method of sampling and acceptance criteria to be applied should all be established as part of the initial protocol.

By conducting three successful cleaning runs, the procedure should be considered validated, but the number of repeats may vary depending on the level of risk, similarity to existing production processes, and/or other soil characteristics.³

CIP validation should be carried out on all newly installed lines, before the product is launched, but new formulation and equipment modification may also grant a re-validation of the procedure.

3) Validation of the fillers and filling environment decontamination

Confidence in the commercial sterility of the filling environment is as critical as that of the product. Aseptic filling machines ensure that the commercially sterile product is not re-contaminated during filling into containers. The aseptic path of the product and the filling environment need to be brought to a condition of sterility, by performing a Sterilisation-In-Place (SIP) operation. This is performed after CIP, and involves treating the filling machine environment with a sterilant (e.g. hydrogen peroxide, steam injection at high temperature, or other approaches).⁴

Validation of the filling zone (i.e. aseptic zone) decontamination (SIP validation) is carried out with microbiological methods, ensuring that sterility is achieved and maintained. For the validation, a microbiological challenge test is conducted; this involves selecting a suitable test microorganism (surrogate), defining its target log-reduction during the SIP process, and determining the most suitable application method and locations for testing within the aseptic zone. The selection of testing locations requires technical understanding of how the SIP process works, the parameters involved, and hence judgement on which areas within the aseptic zone may receive a ‘worst-case’ process.⁵

The validation of aseptic fillers should be carried out for new installations and modifications of existing machines (including transfers and re-installations).

4) Validation of the packaging decontamination

Most aseptic filling machines decontaminate the packaging by either chemical means, (e.g. hydrogen peroxide, peracetic acid), physical means (e.g. UV, plasma, irradiation) or thermal procedures (e.g. saturated steam).⁴ Similarly to validating the aseptic zone decontamination, validating the decontamination of packaging also involves carrying out a challenge test to check what reduction of microorganism can be achieved during the sterilisation of the packaging surfaces.

Typically, a reduction of at least four powers of ten (‘4 logs’) is targeted. The type of microorganism, the inoculum preparation method, and its application to the packaging, will be determined based on the type of sterilant and packaging in question.⁶ When selecting the areas of the packaging to be inoculated, care should be taken in ensuring both internal and external surfaces are considered, as well as any caps and closures (e.g. films) that are applied.⁵

Validation of the decontamination of the packaging should be carried on new filling lines, new packaging and whenever either of these are modified.

5) Microbiological assessment of a test production run

This last step in validating a continuous aseptic line involves incubating and microbiologically assessing a large quantity of finished product samples, produced under normal production conditions. This test is commonly done during the commissioning activities of high throughput lines, manufacturing drinks products.⁷

As preconditions to this activity, the product thermal treatment, CIP, SIP and packaging decontamination should all have been successfully tested and validated. Additionally, a successful sterile test (e.g. incubation and testing of 3,000 finished products containers) would also precede the production test run.

For the test production run, a minimum of 30,000 containers would be incubated and tested (depending on the throughput of the filling machine and other factors, such as number of filling heads), according to a pre-agreed incubation regime and microbiological assessment method. Common assessments include pH measurements and/or microbiological streaking (both destructive), or visual inspection for swelling and clouding.

Provided that the number of failures is lower than the maximum allowed, for a pre-determined statistical sensitivity (usually 95% confidence level), the test is proven successful.

Final Remarks

Validation of an aseptic process line, when expertly performed, provides confidence that the critical parameters required to produce safe food are achieved and controlled appropriately. The importance of validating the sterility of the product, packaging and aseptic filling systems is clear – overlooking even one aspect could compromise the entire operation and result in quality or (at worst) food safety incidents.

An effective validation not only means following a good and sound methodology, it also relies on expert technical knowledge of the subject and the processes.

How we can help

Partnering with a third-party consultancy for aseptic process validations offers additional expert support in data and results interpretation, whether the outcome is expected or not.

Whether you have just installed a new line, made changes to an existing process or product, or are experiencing deviations in the process, leading to spoilage or complaints, our aseptic processing validation and consultancy services can help.

Our aseptic validation package will ensure that your aseptic process achieves the necessary sterility parameters – so you can meet customer and regulatory requirements and produce safe, successful products.

For further information or to request a quote for our services, please contact our experts to discuss how we can help.

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References

• 1. USDA. 2025. HACCP Validation. Available from: https://www.fsis.usda.gov/inspection/compliance-guidance/haccp/haccp-validation
• 2. Codex Alimentarius (Codex). 2008. Guidelines for the validation of food safety control measures (CAC/GL 69 – 2008).
• 3. EHEDG. 2021. Cleaning Validation, Monitoring and Verification (DOC No. 45).
• 4. EHEDG. 2018. Aseptic and hygienic filling machines -planning, installation, qualification and operation (DOC. No. 46)
• 5. IFTPS. 2021. Guidelines for microbiological validation of the sterilisation of aseptic filling machines and packages, including containers and closures. (DOC No.G.005.V1)
• 6. VDMA.2021. Code of Practice – Testing the Effectiveness of Packaging Sterilisation Devices. (DOC. No. 6).
• 7. VDMA. 2020. Guideline to Checking the Microbiological Safety of Filling Machines of VDMA Hygiene Classes IV and V. (DOC. No. 6)