Indicator Organism Testing: Reducing Costs and Time in Product Testing
Microbial indicators are a group, genus, species, strain, or metabolite whose presence or population size indicates the possible presence, population, or activity of another microbe or group of microbes. A classic example is the coliform group - a group of microbes that can grow and ferment lactose at 35°C, producing gas as a byproduct. There are many species of bacteria that fall into this category, but because lactose is a more difficult sugar to ferment than glucose, not all bacterial species fall into the coliform group. However, many enteric human pathogens are coliforms. So, the group has been considered an indicator of poor hygienic and sanitary practices and under certain conditions, the presence and population size of coliforms may correlate with the possible risk of such pathogens. In such situations, coliforms can be a good indicator of risk.
The benefit of using food quality and food safety indicators is the ability to access relative risk by using just a few tests instead of 30 or more to evaluate all possible pathogens and spoilage organisms. Hence, risk can be indirectly measured quickly and cheaply, reducing turn-around time and costs for food and ingredient manufacturers.
There are many indicator tests, so our scientists will work closely to decide a fit-for-purpose approach based on product and process-specific risks. The network of Eurofins Microbiology Laboratories, Inc. companies offers ISO 17025 accredited methods for many indicator organisms of interest.
Common Indicator Organism Tests |
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Key Indicator Organisms
Aerobic Bacteria
Aerobic bacterial are enumerated under an Aerobic Plate Count test which is one of the broader indictor tests used in the food and dietary supplement industry. There are several variations of the test with differing names, incubation temperature, or incubation time. Other names include Total Plate Count, Total Aerobic Microbial Count, Total Viable Count, Standard Plate Count, etc. Drastic method changes such as cold incubation (Psychrotropic Plate Count), anaerobic incubation (Anaerobic Plate Count), or medium change yields method specific counts. Aerobic Plate Count Tests can measure bacteria, yeasts, and molds that can grow on an agar plate in specific conditions. Many, but not all, microbes can be counted with this method; therefore, its use as a broad quality or sanitation indicator is widespread. Greater counts imply poorer quality or suspect sanitary handling condition. Although many pathogens can produce colonies with this test, it is not possible to differentiate pathogenic from non-pathogenic microbes using this method. Meaning a high test count may not always correlate with poor conditions, and thus must be optimized for every product. If you are unsure of which tests are appropriate to run, reach out to our team and we will be happy to support you while making your decision.
Yeasts & Molds
Single-cell yeasts and multicellular molds are fungi that can cause quality defects in foods and ingredients. If allowed to grow in products, some molds can produce secondary metabolites that are toxic, known as mycotoxins. Fungi are widespread in nature so their occurrence is not unusual. Large counts in a yeast and mold test implies the product has likely been exposed to high-moisture environments or contaminated raw materials were used.
Coliforms
Coliforms are a group of bacteria that are widespread in nature – everything from vegetative mater to the intestinal tracts of animals. As an indicator, coliform counts are useful to assess raw material quality and sanitary condition of manufacturing. Finished products and ingredients are expected to have low to non-detectable coliform counts. Such low counts are verification evidence that products have been properly manufactured. A related test is the fecal coliform test. The main difference is a fecal coliform test is incubated at a slightly greater temperature than a coliform test. This elevated temperature selects for a narrower range of coliforms, some of which are not pathogenic but some are (E. coli). It is thought that a fecal coliform test is a better indicator of safety than a coliform test. It does not imply that a food, ingredient, or supplement is contaminated with feces.
Enterobacteriaceae
Enterobacteriaceae are a family of bacteria that share common characteristics. Many of the foodborne pathogens fall within this family, such as Salmonella and E. coli. Because of this association with pathogens, and Enterobacteriaceae count is often used as an indicator of sanitary condition of ingredients and processing environments. This indicator test, however, is not a replacement for specific pathogen tests that may need to be completed for your Food Safety Plan.
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