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How to achieve reliable results with indicator testing methods.

Food safety indicator testing method

The food industry relies on the accuracy and the consistency of microbial testing methods to detect microbial contamination and ensure food safety and quality.1

Historically, the focus has been on testing the finished product as a verification activity to assure food safety. Although important, it is evident that this reactive approach is not always enough to produce safe and quality food for consumers or protect a brand.2,3,4

A modern food safety management system focuses on the entire food process to prevent contamination from reaching the final product and relies on verification activities such as microbial indicator testing.

Samples that are commonly tested include:

  • Input raw materials
  • In-process samples
  • Finished products
  • Environmental samples

Indicator organisms are a group of microorganisms whose presence reflects the general microbiological condition of the food or environment. Consequently, indicator testing can be used to provide an idea of the hygienic status of the processing equipment and environment, to enumerate and monitor the natural flora of foods, validate, and verify process control steps or assess post-processing contamination risks.

Frequently tested indicator organisms include total aerobic plate count, coliforms, and Enterobacteriaceae (hygiene), as well as yeast and mould and lactic acid bacteria (quality).

Enumerating indicator microorganisms in a sample can provide valuable information to develop trends, set baseline levels post sanitation or set specifications for a product, and monitor it for quality and hygiene over time. Based on test results, corrective actions that may be in the form of quality or process improvement can be taken.

Traditional agar testing: an aging method.

Agar testing methods are historically used as reference methods.

Preparing traditional agar dishes is a tedious, hazardous and time-consuming task. It involves many steps, including the handling of boiling liquids and glassware, which can pose safety risks in the lab. Moreover, variation in preparation can lead to inconsistent results. Bulky agar dishes also have a short shelf life and require large incubators and storage spaces.

An innovative testing method made for modernized food science.

3M™ Petrifilm™ Plates are a sample-ready, dry-film with a rehydratable culture-medium system that contains nutrients, a cold water-soluble gelling agent and indicator dyes that facilitate colony enumeration. They are designed with the user in mind, allowing you to get straight to work and maximize your lab efficiency.

3M™ Petrifilm™ Plates offer several advantages compared to agar including:

  • Improved Productivity: They are ready to use, with no preparation required. All you need to do is inoculate, incubate, and interpret.
  • Greater consistency: They offer uniform testing media and are a proven testing method for consistent, reliable results.
  • Compact size: They take up less storage or incubator space.
  • Longer shelf life: 3M™ Petrifilm™ Plates have an 18-month shelf life from date of manufacture.
  • Environmental impact: They are a more sustainable option.

3M™ Petrifilm™ Plates are an easy, convenient way to detect microbial contamination and get consistent and reliable test results every time. Widely used throughout 60 countries, 3M™ Petrifilm™ Plates provide an alternative to traditional agar plates for microbiological analysis. Their reliability is proven and supported by over 105 global validations (AOAC, AFNOR).

3M™ Petrifilm™ Rapid Plates with enhanced features can produce results faster than traditional methods, so you can confidently make time-sensitive decisions.

If you are still using agar dishes for microbial indicator testing, you might be missing an opportunity to not only boost your lab's productivity and accuracy, but also help meet your company's sustainability goals. With 3M™ Petrifilm™ Plates, you can free up time so you can focus on what’s really important: food safety and quality.

Learn more about indicator testing and environmental monitoring.

Download the Environmental Monitoring Handbook by visiting this page to learn more about how you can be proactive about food safety testing in your facility,

For more information on our wide range of testing solutions, contact a representative by filling out the form below.



  1. 3M food safety: microbiological method validation the white elephant in the lab
  2. Shifting the Emphasis from Product Testing to Process Testing
  3. Relevance of microbial finished product testing in food safety management
  4. Environmental Monitoring Handbook for the Food and Beverage Industries chapter 1

About the Author

[enBio=Across the globe, 3M helps companies and individuals succeed every day. All while contributing to true global sustainable development through environmental protection, corporate and social responsibility and economic progress. We are applying our science to make a real impact in every person's life around the world.],[enJob=Food Safety Division],[frBio=Chaque jour, 3M aide les entreprises et les gens à réussir. Tout cela en contribuant au développement durable réel par le biais de la protection de l'environnement, la responsabilité sociale en entreprise et le progrès économique. Nous appliquons notre science afin de faire une différence réel dans la vie de chaque personne dans le monde.],[frJob=Division de la sécurité alimentaire]

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