When it comes to the use of sterile gas for product contact purposes – such as aseptic packaging or product purge applications – no clear guidelines have been adopted by the dairy industry regarding the control of microbial hazards. Practices can often vary from plant to plant. And, as process gases can carry and transfer microbiological contaminants, this issue is clearly of great concern. But can lessons from the pharmaceutical sector can be applied to address this?
A closer look at the problem
Critical control points and HAACP
In order to reduce product contamination, dairy producers in Europe are required to practice hygiene legislation (EU 852/2004) based around the principles of the Hazard Analysis of Critical Control Points (HACCP) framework. Establishing critical control points is one of the seven principles of this:
1. Identification of potential hazards (e.g., pathogenic / spoilage microorganisms)
2. Establish critical control points
3. Establish critical limits
4. Measures to control these hazards
5. Monitoring the controls (e.g., integrity testing)
6. Corrective action
Sterile gas filters are used at critical control points to eliminate bacteria and phage from process gases used in dairy production at point of use applications.
Yet within dairy processing, operators can be reluctant to define many critical control points in the site’s HACCP plan due to the prospect of increased administrative work. And even if sterile gas filters have been identified as critical control points, there is no best practice approach to ensure their on-going performance.
There can also be confusion over how gas fits with the prerequisite programme of the HACCP framework.
Underestimating the threat
There is a lack of awareness of the microbial hazards present in gas among some dairy operators and regulatory auditors. As an example, the atmosphere in milk packaging areas of dairy plants can contain more than 250 cfu/m3 viable bacterial cells, a significant source of microbial hazards to the products being processed. Yet consistent standards are not in place.
Process gases – what is the standard?
In order to protect products from contamination, process gases which come into direct contact with the finished product or finished product contact surfaces should be free from:
- Chemicals (oil droplets, lubricants etc.)
- Particles (scale, metal finings)
- Microbiological organisms (bacteria and phage).
However, details of the specifications can be confusing. For example, air quality is generally expressed in terms of the ISO classifications which specify the presence of three main contaminants; dirt, water and oil. However, there are no specifications for other process gases used in packaging operations. In addition, if the ISO standards for food grade air were transferred to other gases used in dairy processing such as nitrogen and carbon dioxide, there is still no specification for sterility.
What can the dairy industry learn from the pharmaceutical sector?
Validating sterile gas filter performance – lessons from the pharmaceutical industry
In guidance for the pharmaceutical industry (PDA Technical Report 40 - Sterilizing Filtration of Gases), the use of a validated sterilizing grade gas filter is seen as best practice to ensure that all microorganisms will be removed from a fluid stream.
The validation process consists of a bacterial challenge, where the filter is exposed to a fluid stream containing a worst-case number of bacterial or phage/virus cells per cm2 of filter material (typically >107 cfu/cm2). The conditions of the validation process are further defined and categorized and specifications are provided for the different challenges.
Contaminating microorganisms can be present in air and gases in aerosols (bioaerosols) or are present and transferred on airborne atmospheric dirt/particulate. Most bacteria will quickly lose viability if the protective layer of moisture from the aerosol is lost. However, spore-forming bacteria can survive and remain viable in low humid conditions.
Dairy operators should, therefore, use sterilizing grade gas filters which have been properly validated – just as in the pharmaceutical industry – to provide sterility under high challenge conditions against a range of bacteria, including spore formers and phage organisms.
Monitoring sterile gas filter performance – lessons from the pharmaceutical industry
In the pharmaceutical industry, the performance of sterile gas filters is monitored through filter integrity testing. Testing of critical filters usually takes place before and after each product filling campaign.
However, in dairy processing, this practice does not transfer well, as there needs to be a balance between maintaining process security and downtime. In leading dairy process, routine integrity testing usually takes place after the filters have been exposed to several steam in place (SIP) cycles.
There is, however, a solution: automated filter testing devices which use an aerosol challenge – such as Parker Bioscience Filtration’s Valairdata 3 integrity testing unit – are available which can be used to test the integrity of sterile gas filters quickly and easily, minimizing downtime. These solutions can be easily integrated into a HAACP framework.
In the pharmaceutical industry, just as in the dairy sector, the stakes of final product contamination are high. However, in pharmaceutical manufacturing, the performance of critical microbial control processes are more defined and recognized by manufacturing plants and regulatory bodies.
By drawing on the standards used in the pharmaceutical industry, dairy operators can reduce the risk of airborne microbiological contamination.
This post was contributed by Ian Curran, market development manager, Parker Bioscience Filtration, United Kingdom.
Parker Bioscience Filtration offers filtration solutions to protect the quality and taste of beverage products. By working with our application experts, manufacturers can develop a tailored solution to ensure their beverage is free from contamination, full of flavour and visibly clear.