Introducing Flow Cytometry

Revolution or Mere Evolution? Flow Cytometry and Verification of Cleaning and Disinfection in Food Manufacturing Facilities

Food safety depends in large part on the hygienic conditions in food manufacturing facilities. High levels of spoilage bacteria can affect the shelf life and quality of foodstuffs, while the presence of pathogens (such as Salmonella and Listeria) can lead to serious illness. Food manufacturers must be diligent in keeping their processing environment clean and free of pathogenic microorganisms to prevent the cross-contamination of the final product. But how is this currently being done?

Visual inspection

While visual inspection is a prerequisite, it is in and of itself not sufficient. It is a subjective and imprecise means of verifying proper cleaning. More importantly, even if a surface has no apparent residue, this does not mean it is immaculate. Visual inspection cannot ensure that all food residues from the previous run have been cleaned away or that a sanitiser has effectively reduced the microbial level on the surface.

Microbial enumeration with culture-based methods

Generally, there are two ways to perform sampling: contact-based and swabbing-based. With contact-based methods, plates or dip-slides are placed on the surface to be sampled and then incubated. Swabbing-based sampling is carried out with swab sticks or sponges that are rinsed in a buffer solution which is then inoculated into sterile media and incubated. The main limitation of these traditional methods of microbial determination is the amount of time it takes to obtain results. Furthermore, most species of bacteria cannot be cultivated on agar, a phenomenon known as the great plate count anomaly.

ATP detection

Commercial ATP test systems harness the luciferin/luciferase reaction, which is very common in nature, to generate light with the energy provided by ATP. The more light is emitted, the more ATP is present, which could indirectly indicate more food residues or (potentially) more microorganisms. Yet there is one important caveat: as these systems rely on an enzymatic reaction, potential inhibitors or less than optimal environmental conditions could elicit faulty results. Environmental temperature could increase reaction times, whereas light could make it difficult to obtain correct readings. Furthermore, disinfectants can interfere with the reaction, meaning that there may not be a real correlation between living bacteria present on the surface and the results of the ATP measurement. Hence, ATP-based methods are normally used to test surfaces before the application of the disinfectant.

Most foods leave behind residue containing large amounts of ATP, which surpass by several orders of magnitude the amounts contained within bacterial cells. Practically, this means that ATP systems cannot be used to assess the microbial contamination of surfaces in most food processing facilities. Although no bacteria can be directly counted, ATP systems are widely employed because results are generated within seconds, a time-to-result available in no other commonly available technology until now.

What food manufacturers need is a quick method that directly quantifies both bacteria and residue particles and is not influenced by disinfectants and temperature. Although this seems out of reach, the basic technology for making this happen already exists and is being applied today.

Introducing Flow Cytometry

Flow cytometry (FCM) refers to a group of techniques that use optical or electrical signals to detect and measure certain physical or chemical properties of cells and particles suspended in a fluid. Nearly 300 studies conducted between 2000 and 2018 assessed FCM as a tool to characterise microbial water quality. This research was able to illustrate the value of FCM in water treatment, distribution and reuse. There is now a body of research documenting successful applications of FCM robust enough to suggest that it could reasonably and realistically see widespread adoption as a routine method for water quality assessment.

Getting the power of flow cytometry into a handheld device

To make FCM a viable solution for cleaning verification in food processing facilities, it needs to come in a portable format that is simple and easy to use, yet accurate enough to provide reliable counts of bacteria and residue particles in environmental samples. This has been made possible by the use of impedance flow cytometry – a specific kind of flow cytometry which employs an alternating current at varying frequencies which enable the device to detect and count cells and residue particles separately.

Application of impedance flow cytometry to food safety: introducing CytoQuant®

The CytoQuant® impedance flow cytometer is designed for use in just such areas, including food production facilities and clean rooms. Impedance flow cytometry brings considerable advantages to food producers looking to verify their food safety and cleaning programs: the fast and separate quantification of bacteria and residue particles (which can serve as an indicator for the cleaning efficacy), the sensitivity of the method, and the robustness of the swabbing kit and the cytometer itself.

The CytoQuant® system is easy to use, as the device handles all the work except swabbing. CytoQuant® measures the bacteria and particles picked up by the swabs and registers separate results for bacteria and particles and displays them on the screen in 30 seconds.

To experience first hand of this new technology in hygiene verification, register for a free demo here. Alternatively, visit the Romer Labs booth if you happen to be visiting the following tradeshows in September:

Lab Indonesia 2022

Date: 7–9 September 2022

Venue: Jakarta Convention Center

Booth no.: C21

Thailand Lab 2022

Date: 14–16 September 2022

Venue: BITEC, Bangkok

Booth no.: 3H16

Register your visit with us here.

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