Back to Romer Library

Real-Time, On-Site Microbial Testing with Impedance Flow Cytometry: Five Key Benefits and Industry Use Cases

Microbial contamination remains one of the greatest challenges within the food industry. Whether the end product is fresh produce, ready-to-eat meats, or filleted fish, food processors and manufacturers must ensure that bacterial levels are minimized to safeguard both the consumer and the brand. Even today, a century since their introduction, microbial testing largely relies on slow culture-based methods, which often take several days to yield results. These delays—and the guesswork that can ensue—create an environment where quality or production managers may overuse sanitizers, or release products which are not safe for the consumers.

Recent advancements, however, have made real-time, on-site microbial testing feasible in an easy-to-use, handheld format. One of the most notable technologies enabling this is impedance flow cytometry, as embodied by CytoQuant® -a portable instrument offered by Romer Labs. CytoQuant® leverages the principles of impedance flow cytometry to directly count viable microorganisms within 30 seconds, without being influenced by traces of sanitizers and disinfectants.

This article explores how impedance flow cytometry works, why immediate direct microbial counts are a game-changer for the food industry, and how CytoQuant® can be applied in 5 different scenarios. Each scenario highlights a distinct facet of the food industry—showing that, although these sectors differ in production style and target products, they share an overarching demand for speed and accuracy, given their need to ensure strict production hygiene.
 

Microbial Challenges in the Food Industry

From the moment raw materials enter a facility, microbial load becomes a pivotal concern. Uncontrolled bacteria, molds, or yeasts can lead to spoilage, reduced shelf life, and even serious food safety incidents. The last few decades have seen tremendous improvement in hygiene and sanitation. Yet, the tools used to monitor these processes have often lagged behind, especially when it comes to on-site and real-time quantification of microbial load.

Commonly used culture-based methods require plating a sample (such as rinse water, swab eluate, or product homogenate), then waiting 24–72 hours to count colonies. By the time results are available, production has moved on. ATP swabbing, while immediate, does not specifically measure microbial contamination, as most ATP found in food production environments is derived from food matrices. Moreover, trace disinfectants and detergents can quench or enhance the signal, leading to faulty results. This discrepancy can lead to either over-sanitation or under-sanitation, both of which drive up production costs, compromise quality, or risk consumer safety.

Meanwhile, the pace of food production is only accelerating. Demands for fresher produce, more ready-to-eat meals, or more affordable healthy protein sources such as farmed fish all make it challenging to hold product while awaiting microbial test results. There is a growing realization that production managers and quality managers need a tool that is as responsive as their line. Enter impedance flow cytometry - a technique once thought of as confined to laboratory settings, but now increasingly available in a robust, handheld device.
 

How Impedance Flow Cytometry Works

Most professionals in the food industry have encountered the term flow cytometry, commonly used in the testing of raw milk, probiotics and starter cultures, as well as drinking water. Conventional flow cytometry involves labelling cells with fluorescent markers and passing them, one by one, through a beam of light. By analysing how each cell scatters the light or emits fluorescence, it is possible to count them and detect certain properties (such as shape, size, or viability). While powerful, traditional optical-based flow cytometry systems tend to be large, expensive instruments operated by highly trained laboratory staff.

Impedance flow cytometry takes a different approach. Instead of using fluorescence or light scattering, it measures changes in the electrical impedance of a conductive fluid as single particles (bacterial cells, for instance) pass through a measurement channel. Here is a simplified outline of how the process works:

  1. A sample (rinse water, food contact surface swab in diluent, etc.) is prepared and drawn into the device.
  2. The sample flows through a microfluidic channel, where two electrodes apply a small, alternating electrical current.
  3. As individual cells pass between these electrodes, they alter the electrical impedance in a way that is characteristic of viable, membrane intact cells (in contrast to non-viable cells or other types of particles).
  4. The instrument’s algorithm quantifies these signals in real time, converting them into a direct count of viable microorganisms.

One of the main advantages of impedance flow cytometry is that it detects living cells without the need to grow them on media, and therefore without being limited by their ability to be cultivated. This direct approach drastically cuts down on testing time. Additionally, the inherent electrical nature of the detection is less sensitive to chemical interference. Traces of sanitizers can cause problems for ATP-based tests or kill some cells, but with impedance flow cytometry, the device can distinguish living bacterial cells even within a matrix containing these chemicals.
 

CytoQuant®: Bringing Impedance Flow Cytometry On-Site

Previously, flow cytometric methods were inadequate for use in a busy processing facility, on the production floor. They were relegated to specialized laboratories. Romer Labs’ CytoQuant® represents a leap forward: a handheld instrument specifically designed for point-of-need microbial testing. It allows production and quality managers to count viable bacteria in environmental samples—such as rinse waters or conveyor belt swabs - and generate results in just 30 seconds.

Although CytoQuant® is a commercial product, the significance here is broader: it exemplifies how advanced technologies can be made accessible and simple to operate on the factory floor. For production teams and quality professionals, this immediate feedback loop enables them to make informed decisions and thus exert better control.

Here are some of the key benefits that immediate, direct microbial counts bring:

  1. Reduced Waste
    Real-time data means you know exactly if and when a product or production surface is within microbial specifications. This potentially prevents needless disposal of large batches that would pass microbial standards.
  2. Improved Safety
    Verifying that an intervention has been successful helps reduce the chance of a pathogens setting in the processing environment and contaminating the product.
  3. Optimized Sanitation
    Instead of performing time-consuming and costly cleaning and disinfecting routines “just in case,” producers can use real data to focus on the areas that truly need deeper intervention.
  4. Greater Shelf Life
    By keeping cross-contamination in check, manufacturers can secure the product’s shelf life or increase it by employing shelf-life extension technologies (e.g., vacuum packaging or modified atmosphere packaging).
  5. Enhanced Productivity
    Eliminating the waiting period for lab test results helps reduce production downtime. Quality managers can take immediate corrective actions and get the line back up and running.

 

Five Industry Use Cases for CytoQuant®

While all food and feed production environments can benefit from immediate, on-site microbial quantification, some areas see especially significant advantages. Below are six example applications—drawn from common pain points across the food industry—that illustrate how impedance flow cytometry can help optimize both safety and efficiency.

 

1. Fresh-Cut Produce and the Environmental Tradeoffs of Safety and Shelf Life

The Challenge
“Ready-to-eat” fruits and vegetables (washed, cut, and packaged) are in high demand. However, the washing stage is notorious for using large volumes of potable water and sanitizers to reduce cross-contamination. If the microbial load in wash water is too high (sanitizer dosing is ineffective, freshwater rates are too low or the product run is too long), the risk of pathogens such as STEC or Salmonella becoming distributed across an entire batch is also high. On the other hand, if the sanitizer use is too aggressive, the cut produce may suffer in quality.

How CytoQuant® Helps

  • Real-Time Wash Water Checks. If the device shows dangerously high counts of viable bacteria, the wash water is immediately changed, or the sanitizer level is adjusted.
  • Optimized Sanitizer Use: Because the presence of disinfectants does not interfere with impedance flow cytometry readings, it is possible to get accurate bacterial counts regardless of sanitizer levels. This means less guesswork and less risk of over-sanitizing.
  • Reduced Food and Water Waste: By confidently controlling microbial load, producers can avoid discarding borderline produce or wasting large volumes of rinse water when it is not actually necessary.

 

2. Ready-to-Eat Foods and Listeria monocytogenes

The Challenge
Processed meats, soft cheeses, sandwiches, and other ready-to-eat (RTE) products face a persistent threat: Listeria monocytogenes. This pathogen can persist and even thrive in cold, moist processing areas, leading to repeated contamination events. Traditional methods of verifying cleaning and disinfection (e.g., ATP swabs, or slow culture-based tests) may not detect potential Listeria harbourage sites quickly or accurately enough to prevent the pathogen from setting in the facility.

How CytoQuant® Helps

  • Seek & Destroy Programs: The concept of searching for Listeria entry points and eliminating them relies on frequent environmental sampling. CytoQuant® provides real-time viable bacterial counts on surfaces or in rinse waters, serving as a near-instant verification of sanitation effectiveness.
  • Prevent Recalls: Listeria-related recalls are costly, both financially and reputationally. By acting quickly at the sign of elevated bacterial counts, producers can prevent full-scale recalls.

 

3. Fresh Meats and the Fight for Shelf Life

The Challenge
Fresh, vacuum-packed, or modified-atmosphere packaged (MAP) meats are highly perishable. Spoilage bacteria can reduce shelf life, leading to product waste and lost revenue. At the same time, there are strict regulations and consumer expectations around microbial safety. Achieving shelf-life extension depends on rigorous hygiene practices coupled with the right packaging technologies.

How CytoQuant® Helps

  • Immediate Verification of Hygiene: By taking quick swabs of food contact surfaces or analysing rinse water, producers know within seconds if the environment is under control or if a deeper clean is needed.
  • Capture Hard-to-Grow Bacteria: Culture-based methods can miss certain bacteria that do not thrive under typical lab conditions. Impedance flow cytometry picks up a broader range of viable cells, providing a more complete risk assessment.

 

4. Fresh Meat and the Cost of Redundant Sanitation

The Challenge
Meat cutting facilities dealing in raw cuts or carcasses face high labor and resource costs for sanitation. Operators often clean and disinfect equipment repeatedly throughout a shift, erring on the side of caution. While that ensures food safety, it can also add unnecessary downtime and costs, especially if some equipment or areas are already sufficiently clean.

How CytoQuant® Helps

  • On-Site, Immediate Checks: Before deciding to run a full cleaning protocol, the sanitation team can use CytoQuant® swabs to see if bacterial loads are above acceptable thresholds. If levels are low, the cleaning frequency or intensity can be reduced.
  • Precise Resource Allocation: Chemicals, water, and labor hours are expensive. Targeting sanitation only where needed frees resources and time for other production tasks.
  • Reduced Downtime: Minimizing unnecessary cleaning means the production line can run longer without compromising hygienic standards. Over time, these incremental gains add up to major cost savings.

 

5. Fresh Fish and the Delicate Equilibrium Between Freshness, Safety, and Price

The Challenge
Pre-packed, fresh filleted fish is both prized for its freshness and notorious for its short shelf life. Spoilage bacteria flourish in moist conditions, leading to wasted product and high costs. Producers do have shelf-life extension technologies (e.g., MAP or superchilling), but these tools depend on strict production hygiene to avoid introducing even more contaminants.

How CytoQuant® Helps

  • Rapid Quantification: Hygienic status of surfaces, filleting lines, and rinse waters can be checked in a matter of seconds. This ensures that a batch is not exposed to unsafe conditions for extended periods.
  • Confident Shelf-Life Extension: When real-time data confirms very low bacterial counts, the producer can proceed confidently, expecting the product to maintain quality for a specified duration.
  • Reduced Spoilage and Pricing Pressures: By avoiding contamination, the fish can maintain a high level of freshness. Producers may then better align pricing with consumer expectations, rather than rushing to discount or discard product nearing the end of its shelf life.

 

Overcoming the Perception of Complexity

For many production managers and quality professionals, the term “flow cytometry” still suggests a large, stationary device requiring specialized laboratory operators and sample preparation. Yet devices like CytoQuant® illustrate that technologies once considered too complex for the factory floor have evolved. Portable, handheld, and battery-powered, these systems come with straightforward sampling protocols and user-friendly software interfaces.

In practice, adopting impedance flow cytometry can be as simple as:

  1. Swabbing or collecting a small fluid sample (e.g., rinse water).
  2. Preparing the sample as per the instrument’s guidelines (often involving minimal pipetting or dilution).
  3. Inserting the sample cartridge into the handheld device.
  4. Waiting 30 seconds for a direct reading of viable bacterial counts.

This approach makes it feasible to monitor multiple points in a production line, gather real-time data, and document results electronically. Managers can visualize trending data or integrate the results into broader quality management systems.

 

Conclusion

In an era where consumers demand fresher, safer, and more sustainable food products, immediate onsite microbial counts present a major leap forward. CytoQuant®, powered by impedance flow cytometry, exemplifies how once-laboratory-bound technologies can evolve into practical, accessible devices suitable for daily use in a hectic production environment.

From fresh-cut produce to RTE meats, fresh fish, and more, real-time viability assessments allow producers to precisely balance sanitation needs, cost constraints, shelf-life requirements, and overall quality. The result is a streamlined process that simultaneously reduces waste, lowers recall risk, and preserves product integrity.

Far from being “too sophisticated” for everyday use, impedance flow cytometry is now within reach of production and quality managers. By harnessing the power of electrical impedance changes at the cellular level, food processors can make data-driven decisions that keep contamination risk low, ensure compliance, and ultimately protect the consumer - without missing a beat in their production schedule.

It is this kind of technology-driven efficiency that will shape the future of food safety. As more facilities adopt direct microbial quantification devices like CytoQuant®, the food industry will continue to shift away from a reactive approach and toward proactive, precision-based methods of quality control. In doing so, producers can improve their bottom line, preserve precious resources, and most importantly, protect the health of the public they serve.

Published on:

Microbiology