Microbiological limits and testing food microorganism levels
Microbiological testing helps show your food has safe levels of microorganisms and your production or hygiene procedures work. These documents are on microbiological limits in food and beverages.
Food safety can only be assured by the use of risk-based programmes based on the principles of HACCP. Reliance on microbiological limits and product testing alone is not sufficient. Microbiological sampling of end products is a means of verifying that the control systems in place are working. There is little point in sampling if the control measures are not in place.
Which microbiological limits do I use?
There are several documents and pieces of specific food product legislation that you need to consider when you interpret microbiological results.
The first documents to consider are those that are part of New Zealand food law, including the FSANZ Standard 1.6.1. It is unlawful to exceed the limits defined in this standard. Find out more:
When deciding on a sampling plan and interpreting its results, you also need to consider limits outlined in specific food product legislation, such as dairy or animal product legislation.
MPI specifies product outcomes for all dairy produce and products. Find out more:
The microbial limits associated with animal products for human consumption are outlined in notices issued under animal product legislation. Find out more:
Note: The limits identified in legislation take precedence over any other levels outlined in the following guidance documents.
The two main sources of guidance are the following:
- FSANZ Compendium of microbiological criteria for food
- Microbiological reference criteria for food [PDF, 121 KB]
These documents provide guideline levels for certain other microorganisms and foods. When no standard (microbiological limit) exists in law, food businesses and regulators may use the suggested microbiological guidance limits in these documents to help verify the microbiological safety of a manufacturing process or the safety of food. If these guideline levels are exceeded, it generally indicates a problem in the food production process or hygiene procedures that should be addressed.
Regulators may also use the limits contained in these documents to interpret the results of microbiological testing. Regulators may also use these results to
- reinforce other observations made on food safety practices and the processing environment
- support a conclusion that the food process is not controlling microbiological contamination or growth sufficiently to prevent unsafe food being produced, thereby not meeting legislative requirements.
'Acceptable' and 'defective' microbiological levels
Microbiological limits are generally expressed as 2- or 3-class plans with an m value below which processing/product is considered 'acceptable' and an M value above which processing/product is considered 'defective'. Between these values, processing/product is considered 'marginal'.
When undertaking end-product testing, it is important that the following issues are considered:
- Testing alone does not confirm the safety of a food product. It gives an indication that the controls in place in your business are working.
- Sampling plans should be consistent with guidelines established by the International Commission on Microbiological Specifications for Foods (ICMSF). Microbiological testing laboratories will be able to give advice to businesses on how to design appropriate sampling plans.
- Food businesses should not use the 'defective' limit as an upper limit for process control. Food businesses should identify limits that are achievable for their food process. These would be expected to be lower than the 'defective' limit for businesses operating under a Risk Management Programme (RMP), a Food Control Plan (FCP), a Product Safety Programme (PSP), or another programme under which good hygienic practices are standard. Process control limits should be reviewed regularly, particularly if processing conditions change in any way. Such reviews should be included as part of the commissioning of new processes and equipment or during a review of HACCP.
- The number of samples taken must comply with the requirements of the relevant document (usually a minimum of 5 samples are required, per batch of a particular food product).
- Ensure that the organisms chosen for testing in a product will provide useful information.
- Before you sample, determine and document what your actions will be with regards to all possible results.
Note that microbiological limits for imported foods are not covered in this guidance note. Find out more:
Reviewing Standard 1.6.1 – Microbiological Limits for Foods
FSANZ is reviewing Standard 1.6.1, which became part of the Food Standards Code in 2000. The review is looking at what microbiological limits are required and for what purpose. For example, microbiological limits may be set to determine the safety of a specific batch of food (food safety criteria) or to verify that the production process or good operating practices is working (process hygiene criteria).
The review is considering microbiological limits applicable to different food product types. To date the review has considered :
- Listeria monocytogenes in ready-to-eat (RTE) foods
- Raw milk products
- Powdered infant formula products
- Poultry products
Read a background paper and find out more about the review, including its scope, principles, and guidelines:
Two sets of criteria for L. monocytogenes now apply, based on whether growth of L. monocytogenes will or will not occur in the RTE food:
- RTE foods in which growth of L. monocytogenes will not occur (less than 100 cfu/g).
- RTE foods in which growth of L. monocytogenes will occur (not detected in 25 g).
Guidance documents for Listeria
Refer to the following 3 fact sheets for guidance on the application of microbiological criteria for Listeria monocytogenes in RTE foods:
- FSANZ guidance on the application of microbiological criteria for Listeria monocytogenes in RTE foods
- Food Standard 1.6.1 Listeria in RTE foods [PDF, 162 KB]
- Listeria in fresh salads, sprouted seeds, smoked seafood [PDF, 134 KB]