Hygienic validation of closed systems

As a company, how can you be sure that a closed-loop system is sufficiently clean? EHEDG trainer Martin Barnickel shares in EHEDG Connects his valuable insights for optimizing the food safety of closed systems through the application of cleaning validation techniques.

How important is validation to ensure food safety?

Whether you are working as a safety manager within a food company or developing components for closed food processing or packaging processes, there is nothing more reassuring than thorough quantifiable validation of cleaning processes. To ensure food safety, certain physical, chemical and biological hazards must be considered and validated.

What are the specific challenges for closed processes?

In closed processes, the risk of a wide range of food safety hazards increases, such as microorganisms and their toxins, residue from products or cleaning, disinfecting or lubricating agents, or unwanted food ingredients from previous product batches that may contain allergens. Therefore, there is always a need for regular and efficient cleaning, with or without disinfection and sterilization. But not every facility can be easily cleaned thoroughly, with potentially enormous consequences ranging from limited physical complaints to food poisoning and sometimes even deaths.

In your publications you talk about the kinetics of contamination? Could you please elaborate on this?

To that end, let's look at a process from the dairy industry: pasteurization. In these closed systems, microbial growth and contamination often occurs during preheating and in the heat recovery phase when temperatures dip below 55 °C. Precise monitoring and documentation of conditions during pasteurization (usually 75 °C for at least 15 seconds) is an absolute prerequisite to then ensure food safety. As a general maxim, no one should settle for mere disinfection techniques if sterilization is technically feasible.

Can you share another example with us?

Another example of the kinetics of contamination is a contamination hazard related to a leak in a plate exchanger. Indeed, pathogenic microorganisms can then cause contamination of the product. Plate exchangers are therefore better checked for leaks at least twice a year. The plates themselves should not have been in use for more than five years. As a general rule, pasteurized products should not be processed for more than 20 hours without CIP, even if the equipment was sterilized at the start. Other hazards arise from deteriorating sanitary conditions due to aging facilities. Therefore, processing facilities should be regularly tested for cracks, cavities, voids and leaks. Knowing that sterile products are sometimes processed for days at a time without cleaning in between, the facility must be completely free of empty spaces, bacteria-proof and operated in a professional manner so as not to be a source of contamination.

What are the main validation criteria?

To assess the efficiency of a cleaning program, the first thing to look at is the differential TOC analysis of the rinse water. Mere visual inspection or the absence of odors and biofilms as a means of control is totally inadequate. TOC analysis is the basis for any validation. In addition, UV light and certain dyes can help to trace traces of product residue (> 4µg/cm²). For places that are difficult to reach and clean, an endoscope provides relief to perform a visual inspection. Nevertheless, in many cases periodic disassembly of the closed system will be appropriate. But since it is virtually impossible to always rule out all contaminations, hygienic plant design, the use of residue-free cleaning agents and efficient sterilization are, in practice, mandatory costs. The monitoring techniques used should quantify the degree of hygiene before and during production. Problematic biofilms can only be avoided by timely cleaning. The rise in differential pressure can be seen as an alarm system. In addition, biological parameters such as ATP content, TDC, AOC/TOC and BFR are of interest for assessing the hygiene level after CIP or SIP.