Monitoring Microorganisms in a Food Plant

An effective sanitation program should remove food debris, organic material, and soil from areas that may support the survival or growth of microorganisms. The master cleaning schedule (MCS) and sanitary standard operating procedures (SSOPs) are key programs to guide cleaning activities.

How do you know if all these efforts are successful? Successful sanitation can be measured by a number of means, such as visual inspection, microbiological testing for indicator bacteria using sponge sampling, or swabbing.

What does a microbiological environmental monitoring program consist of? Following are some practical QA solutions to monitor microorganisms in a food plant, based on discussion with Edward R. Richter, president of Richter International (a Columbus, Ohio-based private consulting laboratory specializing in food safety services) and fellow member of the Strategic Alliance of Food Experts (SAFE).

Although food processing equipment may pass an organoleptic observation, it does not necessarily mean that bacteria have been reduced to a safe level. Microbiological testing includes testing of pathogens as well as indicator microorganisms. The types of bacteria, target pathogen(s), sampling locations, and testing frequency should be incorporated into a microbiological monitoring program specific to each food plant.

The goal of such a program is to determine if the processing environment is in microbiological control. Understanding the level and types of microorganisms in various environmental areas allows potential problems to be corrected before finished product could be impacted. Microbiological control also means knowing that microorganisms are not proliferating in an environment.

There are a variety of ways to monitor microbiological quality of a food plant. Many companies rely on quick read systems such as ATP (adenosine triphosphate) swabs to verify sanitation efforts. While these systems provide a success indicator after cleaning and sanitizing, they do not reflect the status of the environment during production. Microbiological samples collected post sanitation also do not reflect conditions during production. Sanitation verification is an essential part of quality assurance and food safety, but it is only one aspect of an environmental program. An overall microbiological sampling program should include product contact surfaces, with samples taken during production. In-process samples are a direct indication of the overall microbiological control of the finished product.

An effective microbiological environmental program should include testing for pathogens as well as indicator organisms such as Enterobacteriaceae. Results from these analyses should be compiled into a format that provides an easy understanding and interpretation of trend data by qualified quality assurance and food safety personnel. Data from a properly executed microbiological environmental program should reveal issues in sanitation, air quality, personnel practices, lack of SSOP compliance, and/or sanitary design influencing the microbiological quality of the finished product. For example, Salmonella will typically contaminate a finished food product through the environment.

Four elements of a microbiological environmental monitoring program should include:

1. Air Monitoring. Microbiological air monitoring is critical, since what falls out of the air can fall onto product and food-contact surfaces. It is suggested that weekly air-monitoring samples be collected with air impingement total microbial counts (fungi and bacteria) having an acceptable limit of <250 colony forming units (CFU) per 15-minute exposure.
2. Pre-Operational. This type of microbiological monitoring is a verification of proper cleaning and sanitizing of food-processing equipment. Total microbial counts are the typical analysis used with an acceptable limit of <100 CFU per sponge.
3. In-Process. This is a common program for food-plant verification of microbial control. Enterobacteriaceae is recommended as the indicator of appropriate microbiological control. A typical specification (acceptable limit) of <100 CFU per sponge is often used, but this can be as high as <1,000 CFU per sponge. Both food contact and non-food contact surfaces are included as sampling sites.
4. Pathogen. This program is essential. A common target species for many food plants is Salmonella. More recently some food plants with high meat constituents include Listeria in their pathogen program.

Since sanitation programs are typically separated into four zones, a microbiological environmental monitoring program should follow the same concept. An effective microbiological environmental monitoring program will provide early warning for potential microbiological hazards in a food plant, identify issues, provide science for source investigation, and assure overall microbiological control.